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Quincy

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  1. Quincy
    The image is comprised of snowfall totals from various sources, some of which include the New England forum on here. Snowfall totals across Connecticut were pretty uniform around 3-4", although slightly lower amounts occurred along I-95 and there were a few isolated amounts around 5".
    I'll post a contoured color map within the next 12 to 18 hours.
  2. Quincy
    The National Weather Service (NWS) reported that an EF-0 tornado touched down in eastern Massachusetts Thursday afternoon, shortly after 4:30 p.m.
    An upper level low lifted northward through New England on Thursday. An unseasonably cold air mass was in place, resulting in cold temperatures aloft. It was the combination of low Lifted Condensation Levels (LCL's) and moderate wind shear aloft that helped create an environment that was marginally supportive of tornado development. It is possible that a land-sea interaction with winds off of the nearby ocean may have played a role in spawning this tornado. The NWS reported that it was a case of a cold air funnel.
    The tornado touched down in Stoughton, M.A. in Norfolk County and stayed on the ground for 0.25 miles. The tornado was a strong EF-0 with maximum sustained winds of 85 MPH. Damage was minimal, but a local car dealership reported seeing the tornado and had some vehicles blown around by the winds.
    Looking back at historical tornadoes in the Northeastern United States, the helicity values and amounts of instability in place on Thursday were relatively low compared to prior tornadic events. However, it was the low LCL heights and moderate wind shear that did elevate the tornado potential somewhat. On a scale of 0-5, 0 being unfavorable and 5 being highly favorable for tornadoes (based on local climatology), the environment yielded a value of 1.9.
    A note that a 2.5 value would be equal to the mean of past tornadoes.
    PUBLIC INFORMATION STATEMENT
    NATIONAL WEATHER SERVICE TAUNTON MA
    158 PM EDT FRI MAY 10 2013
    ..TORNADO CONFIRMED IN STOUGHTON IN NORFOLK COUNTY MA
    LOCATION...
    STOUGHTON IN NORFOLK COUNTY MA
    DATE...MAY 9 2013
    ESTIMATED TIME...431 PM EDT
    MAXIMUM EF-SCALE RATING...EF0
    ESTIMATED MAXIMUM WIND SPEED...85 MPH
    MAXIMUM PATH WIDTH...50 YARDS
    PATH LENGTH...0.25 MILES
    BEGINNING LAT/LON...42.10N / 71.10W
    ENDING LAT/LON...42.10N / 71.10W
    * FATALITIES...0
    * INJURIES...0
    * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN
    NWS STORM DATA.
    ..SUMMARY
    THE NATIONAL WEATHER SERVICE IN TAUNTON MA HAS CONFIRMED A BRIEF TORNADO TOUCHDOWN IN STOUGHTON MA ON MAY 9 2013.
    THE TORNADO TOUCHED DOWN AT A CAR DEALERSHIP ON ROUTE 138 WHERE IT WAS CAPTURED BY A SECURITY CAMERA AND RECORDED ON CELL PHONE CAMERAS BY SEVERAL OF THE DEALERSHIP EMPLOYEES.
    THREE RV TRAILERS...WEIGHING ABOUT 5000 POUNDS EACH...WERE PUSHED BACK ABOUT 6 FEET AGAINST A CHAIN LINK FENCE. ONE TRAILER WAS LIFTED ABOUT 15 FEET INTO A LIGHT POLE BUT LANDED ON ITS WHEELS WITH MINIMAL DAMAGE.
    AN ALUMINUM DOOR ABOUT 20 FEET HIGH AND 15 FEET WIDE WAS BLOWN OUT OF THE SERVICE GARAGE. EYEWITNESSES REPORTED CEILING TILES BEING LIFTED INSIDE THE DEALERSHIP AS THE TORNADO PASSED OVERHEAD.
    THE TORNADO ENTERED A WOODED AREA JUST TO THE NORTHEAST OF THE DEALERSHIP. ABOUT 0.25 MILES AWAY...TWO LARGE PINE TREES WERE DOWNED ON ERICA DRIVE AND DEAN ROAD BEFORE IT DISSIPATED.
    BASED UPON A SURVEY OF THE DAMAGE...THE TORNADO IS CLASSIFIED AS EF0 ON THE ENHANCED FUJITA SCALE WITH MAXIMUM WINDS OF 85 MPH. THE PATH LENGTH WAS 0.25 MILES AND THE MAXIMUM WIDTH WAS ABOUT 50 YARDS.
    Here's a look at radar imagery about a half hour before the time of the tornado:

    The Supercell Composite Parameter was relatively low, although some slightly higher values did target the area near the tornado touchdown:

    The only severe weather report in the Northeast on Thursday was that tornado in Massachusetts!
  3. Quincy
    Here are some snowfall maps that I created using reports from various sources. Many of the reports came from this forum and the National Weather Service. Only social media reports that passed through quality control were considered. It should be noted that some of the reports include sleet.
    A general 4 to 8 inch snowfall blanketed the state before a changeover to sleet and in some cases freezing rain/rain. Very few totals deviated from that range, except for a few 8"+ reports in northwestern Connecticut and totals less than 4" across coastal New London County.
    Precipitation came in multiple waves between December 14th and 15th. Periods of light snow fell from morning through early afternoon. Radar imagery showed pronounced dryslots and breaks in the snow shield through much of the afternoon and early evening hours before a slug of heavier precipitation moved back in. This lack of steady snow likely cut down on some of the snowfall totals.
    Warmer air began to work north overnight as low pressure developed along the New Jersey coast. It took quite some time to erode the cold air that was in place prior to the event. Even though areas such as KGON and KIJD changed to rain, KHVN never rose above freezing during the steady precipitation. There, there was even a pronounced temperature drop of 7 degrees within an hour around midnight as the wind shifted to the north, allowing for colder air to drain into the city. As a result, New Haven and nearby North Haven reported an ice accretion of 0.3 inches. Other areas between I-95 and I-84 saw some icing, but most of the freezing rain was confined to lower Fairfield and lower New Haven Counties.
    If any amounts you reported conflict with these amounts, please comment back with your total(s).
    Here is an alternate black and white version of the map:

  4. Quincy
    Over a 50-year span from 1962 to 2011, the most violent (F/EF-4 and F/EF-5) tornadoes occurred over Oklahoma and Mississippi. The maximum grid-points reported 16 over that period, with two of those grid-points in central Oklahoma and one in central Mississippi.
    While a broad area from the Plains to the mid-South sees the most tornadoes overall across the United States, there are three sub-areas with the most violent tornadoes. Much of Oklahoma falls into that category, as it is widely considered to be in the heart of tornado alley. Further north into Iowa is another area that has seen the most violent tornadoes during the period. The third area falls across Mississippi, where the tornado season is relatively elongated from the heart of winter into mid-Spring. The tornado season in Oklahoma generally occurs in a narrower window in mid-Spring. The season in Iowa tends to fall from mid to late spring with a secondary peak in the fall. A smaller and less significant maximum for violent tornadoes can also be identified across the upper Ohio Valley. While the tornado season tends to peak there in mid-Spring, a few events have also occurred in the fall.
    An interesting tornado minimum occurs in a small portion of central Missouri. Among multiple factors is the unique geographical area Missouri falls into. The classic tornado setup in the Plains is driven largely by lee-side cyclogenesis and the dryline. As storm systems move across the Plains, the bulk of the violent tornadoes tend to occur west and northwest of Missouri. Also, the dryline tends to have trouble advancing enough east to penetrate far into Missouri. Likewise, typical tornado events in the mid-South tend to thrive off of moisture from the Gulf of Mexico, producing tornadoes east of Missouri. With that said, higher instances of violent tornadoes have been noted across northwestern Missouri (tornado alley), far southeastern portions of the state (Dixie alley) and the devestating EF-5 tornado in Joplin, in far southwestern Missouri in 2011.
    East of the Appalachians, violent tornadoes are fairly uncommon. However, two particular regions have reported three or more violent tornadoes from 1962 to 2011. Portions of the Carolinas fall into that category. Further north, grid-points in the mid-Hudson Valley into southwestern New England have reported four violent tornadoes in that same span.

  5. Quincy
    I see this event as a widespread 2-4 incher across most of interior SNE. The tough call comes along I-95 for BOS-PVD-GON, as often is the case. I do think most areas even along the South Shore get a thump of snow/sleet at the beginning.
    I'm not really all that confident on widespread 4"+ amounts, but I've outlined an area with a black dotted line that could see locally 5-6 inches.
    I also expect precipitation to quickly shut off in the morning (by 7 or 8 a.m. across much of Connecticut) and taper to drizzle near and SE of I-84 with pockets of "snizzle" or flurries/freezing drizzle across the higher terrain.
    Connecticut Forecast:
    On the shoreline...(< 2 inches)
    Although there may be a period of snow and sleet, temperatures near the ground will likely remain above freezing through most of the event. Combine this with with a changeover to plain rain and areas near the coast should see less than 2 inches of snow/sleet.
    Inland...(generally 2-4 inches)
    Most areas should see a period of moderate snow before a changeover to sleet. Precipitation may actually end as a period of drizzle late Wednesday morning, with pockets of freezing drizzle in the hills. Before the changeover, generally 2 to 4 inches of snow/sleet is expected.
    Highest elevations...(locally 4"+)
    Due to colder air in place, Litchfield County and northern Tolland County may stay near or below freezing throughout the entire event. The end result is NEAR 4 inches of snow with localized totals that could reach perhaps 5 or 6 inches.
  6. Quincy
    Two tornadoes (an EF-2 and an EF-1) touched down in eastern New York on Wednesday, both around 7:00 p.m., according to the National Weather Service (NWS).
    The stronger tornado, an EF-2, had winds of up to 125 MPH and caused damage along a relatively wide and long path. The tornado width was estimated at 1 mile wide with a track length of 17 miles from Florida to Rotterdam.
    The second tornado formed just to the southwest of the EF-2 tornado, around the same time. It was a weaker and shorter-lived tornado, but was associated with the same powerful squall line that was moving east-southeast across New York.
    An upper level shortwave disturbance passed across New York state on Wednesday. Daytime heating across the state helped destabilize the atmosphere. Veering winds aloft created an environment that was conducive for the formation of tornadoes.
    I was actually chasing the EF-2 tornado, but was too far west to catch up to it. Heavy rain, flash flooding and traffic didn't help matters. As I drove into the Rotterdam area along I-90, I noticed cars parked under overpasses. While they may have not witnessed the tornado, I'm sure they experienced strong winds and may have been aware of the Tornado Warning. Personally, I did not see a lot of damage, but the tracks of the tornadoes were mainly south of I-90, which was my route of travel.
    PUBLIC INFORMATION STATEMENT
    NATIONAL WEATHER SERVICE ALBANY NY
    1209 PM EDT FRI MAY 31 2013
    ...PUBLIC INFORMATION STATEMENT...
    TORNADO TOUCHDOWN IN MONTGOMERY AND SCHENECTADY COUNTIES ON WEDNESDAY MAY 29 2013.
    LOCATION...
    BEGAN IN FLORIDA IN MONTGOMERY COUNTY NEW YORK TO ROTTERDAM IN SCHENECTADY COUNTY NEW YORK.
    DATE...05/29/2013.
    ESTIMATED TIME...647-700 PM.
    MAXIMUM EF SCALE RATING...EF-2.
    ESTIMATED MAXIMUM WIND SPEED...125 MPH.
    ESTIMATED PATH WIDTH...1 MILE WIDE.
    PATH LENGTH...17 MILES.
    BEGINNING LAT/LON...42.8457/-74.2034
    ENDING LAT/LON...42.8042/-74.0208
    * FATALITIES...NONE.
    * INJURIES...1.
    * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT AND PUBLICATION IN NWS STORM DATA.
    SUMMARY...PATH WIDTH WAS CONSISTENT ALONG THE ENTIRE PATH LENGTH. MAXIMUM DAMAGE INCLUDED ROOFS TORN OFF OF MULTIPLE STRUCTURES AND HIGH TENSION POWER LINE TOWERS TOPPLED. LARGE NUMBER OF HARD AND SOFT WOOD TREES WERE EITHER TOPPLED...UPROOTED AND OR SHEARED. WIDESPREAD POWER OUTAGES OCCURRED AS WELL.
    ******************************************************
    PUBLIC INFORMATION STATEMENT
    NATIONAL WEATHER SERVICE ALBANY NY
    1241 PM EDT FRI MAY 31 2013
    ...PUBLIC INFORMATION STATEMENT...
    TORNADO TOUCHDOWN IN SCHOHARIE COUNTY ON WEDNESDAY MAY 29 2013.
    LOCATION...
    SUMMIT AND EAST JEFFERSON IN SCHOHARIE COUNTY NEW YORK.
    DATE...05/29/2013.
    ESTIMATED TIME...657 PM TO 702 PM.
    MAXIMUM EF SCALE RATING...EF-1.
    ESTIMATED MAXIMUM WIND SPEED...100 MPH.
    ESTIMATED PATH WIDTH...200 YARDS.
    PATH LENGTH...2 MILES.
    BEGINNING LAT/LON...42.515196/-74.554181
    ENDING LAT/LON...42.522471/-74.578385
    * FATALITIES...NONE.
    * INJURIES...NONE.
    * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT AND PUBLICATION IN NWS STORM DATA.
    SUMMARY...BRIEF TOUCHDOWN ALONG RIDGE LINE SEEN FROM JUNCTURE OF DUTCH HILL ROAD AND WHARTON HOLLOW ROAD. DOZENS OF SOFT AND HARD WOOD TREES FALLEN IN DIFFERENT DIRECTIONS AND SHEARED OFF. ALSO TREES DOWN IN DIFFERENT DIRECTIONS ALONG ENID ROAD AND PERAGLIA ROAD.
    Here's a look at radar imagery at 7:00 p.m. when both tornadoes were on the ground:

    Notice overlap of strong bulk wind shear and MUCAPE leading up to the touchdowns:

    Here's a look at storm reports from across the area:

    Here are the tornado tracks to date (2013) in the region:

    Here's a look at my closest pass to the EF-2 tornado, which was basically at the time that it was reported to have lifted off the ground:

  7. Quincy
    The potential exists for a low-end severe weather outbreak across portions of the Plains this weekend, April 12th-13th.
    The first focus is on Saturday afternoon into the overnight period across the central Plains. Surface low pressure is forecast to move to a position in the vicinity of the Oklahoma panhandle by 00z Sunday. Now while there is good agreement among the models of destablization in the warm sector, capping will likely mitigate any convective activity for most of the day. However, by late afternoon and into the evening hours enough of the CAP may erode to allow for some isolated severe thunderstorms.
    In the upper levels, a broad positively-tilted trough is projected to be crossing the Rockies late Saturday. The NAM and GFS show an embedded, but small vortmax being ejected northeast from Kansas toward the Missouri/Iowa border Saturday night. Wind fields are not overly impressive and the 18z NAM low level jet appears overdone. With that said, at least 30 knots of bulk wind shear is modeled.
    CAPE values via the NAM and GFS exceed 2000 J/kg from Oklahoma up into Kansas and northern Missouri. The Euro has increased instability somewhat from the 00z run, but only maxes out values around 2000 in eastern Kansas. Given the amount of CIN that has to be overcome, the severe potential here is marginal at best. Given the time-frame three days out, the exact positioning and severity of this threat could shift.

    A somewhat more favorable severe setup may develop on Sunday. As the upper level trough digs into the southern Plains, surface low pressure deepens and slides southeast through Oklahoma and into northern Texas. With the trough axis approaching a neutral tilt, the overall dynamics alone become supportive for severe thunderstorms.
    At the surface, low pressure matures across far northern Texas Sunday afternoon as a strong cold front quickly dives south. A moist southerly flow will aid with moisture transport as dew-points move into the mid and upper 60s. The GFS also shows lifted indicies as low as -12. Ahead of the dryline, a moderately unstable air-mass is forecast on both the GFS and Euro. The GFS has 1500-2500 J/kg of CAPE across eastern portions of Texas into southern Oklahoma with the Euro showing similar instability levels. There should not be much capping, so convective can initiate ahead of the dryline with isolated supercells possible in the warm sector as well.
    Kinematic support increases with bulk shear in excess of 50 knots possible further south of the low across Texas. While damaging winds and hail may be the most significant threats, the setup may also be supportive of at least a few tornadoes. Severe thunderstorms could continue into early Monday, with at that point the cold front should have overtaken the dryline. The result would be more of a squall line with potentially damaging winds than discrete supercell structures. If the somewhat faster GFS is correct, the threat would extend further east into Arkansas and Louisiana.
    While confidence is greater in the severe threat on Sunday, a faster-moving cold front or weaker storm system could alter the forecast. There is relatively narrow window during the second half of Sunday that this system must align with in order for severe weather to be a significant concern. A quick note that the 18z GFS has trended toward stronger kinematic support for Sunday.
  8. Quincy
    Map above is based on reports from various sources, including this board, the National Weather Service and data viewers from across the state sent in.
    Event Summary:
    Scattered snow showers reached portions of western Connecticut by late morning on the 29th. This snow was associated with weakening low pressure over Pennsylvania.
    The main storm began to develop east of Virginia during the afternoon.
    Steady precipitation overspread the state from southwest to northeast between about 1 and 3 p.m. Most areas saw snow, but some ice pellets and graupel were reported near and southeast of I-95. Coastal New London County even switched to rain for a time.
    Colder air moved in and a heavy band of snow set up over central and eastern Connecticut.
    Snowfall rates between 1 and 3 inches per hour hammered portions of New Haven, Middlesex and New London Counties. This area of heavy snow eventually moved northeast and also impacted Tolland and Windham Counties. This band was a bit more intense than some predictions, resulting in higher snowfall amounts than forecast.
    Extreme western Connecticut was too far west to be affected by this heavy snow.
    The heaviest snow fell between about 4 p.m. and 9 p.m. before the shield of precipitation began to break apart. After midnight, the only leftover precipitation was occasional snow showers. By then, the bulk of the accumulation was over.
    I still find the Feb. 7, 2003 analog to be quite good for this event, with respect to Connecticut. It's clear that with a warmer solution, southeastern Mass. could not have had such high snowfall amounts.
    Shift the axis about 75 miles SW and you get a VERY good match-up. This analog showed up as a strong match about 2-3 days before the event: The point was that interior eastern Conn. and NW R.I. was favored for the highest amounts.

    Forecasts for the storm were decent within 24 hours of the event, but before that, most were playing catch-up. What was expected to be a minor event turned into a moderate one with several snowfall totals in the 10-12 inch range, especially across eastern Connecticut.
    My own forecast (from 5 p.m. the night before the storm) was too high for areas SW of Conn. and was generous as well for eastern Mass. With that said, I could have also pushed the 6-10" zone back further west:

    The image below shows approximate snowfall totals from across the region:

    Heavy snow focused in on the eastern half of Connecticut and the radar image below shows moderate to heavy precipitation pounding southern portions of the state. At the same time, some observed 2 to 3 inches of snow per hour for a few hours.

  9. Quincy
    Thanks to some feedback, I cleaned up this map and added a few additional reports.
    There are still some gaps in Litchfield County, a report of 4.0 inches in Torrington made more sense based off of observations and radar imagery for that area. You can see how the higher amounts were generally confined to the higher terrain, with lower amounts in the Conn. River and Shetucket River valleys.
    Below is a color, contoured map I put together:

  10. Quincy
    This isn't really a big event, but due to the amount of discussion it's had, I felt a map was warranted.
    Low pressure moving through the Great Lakes brings an usual push of generally light snow towards the Appalachians. A new area of low pressure is forecast to form east of the mid-Atlantic region, enhancing snowfall amounts ever so slightly around the coastal plain. This map does not show it, but light snow should extend southward into Virginia.
    I believe that most areas will see an inch or less of snowfall, with interior Mass. seeing little or no snow at all. I'm not even all that confident for 3" amounts, but I added them as a potential outcome for northern Pennsylvania, the outer Cape (Cod) and the Islands of southeastern Massachusetts.
    The column is fairly cold, from the surface right up through 850mb and 700mb, promoting snow growth and higher than "typical" liquid to snowfall ratios. I could see 15:1 ratios on the shoreline and 20:1 further inland. The end result is a light, fluffy snow that pretty much sticks on contact to most surfaces.
    Basically, most areas may see up to an inch, with the highest probability of 1"+ amounts occurring along and south of a line from Binghamton to Bridgeport to Groton to Providence to Taunton.
  11. Quincy
    I expect light snow to reach the NY/CT and NY/MA border around 9 a.m. or so and then overspread the area from west to east. The heaviest precipitation amounts impact northern Connecticut into central and western Massachusetts.
    Quick warming at 850mb should push most areas over to sleet and freezing rain. The cold layer aloft up to about 925mb looks deep enough where the inland hills may get a thump of sleet, while the interior coastal plain could see several hours of freezing rain.
    By late afternoon precipitation tapers off, but freezing drizzle could linger for many inland areas through much of the night.
    Basically expecting 1-3" of snow and sleet, followed by a glaze of ice for inland areas. Best shot at 3" is across the higher terrain of the Berkshires and Worcester County. Keep in mind that this total accounts for snow AND ice. The only area that is a bit of a question mark is the I-95 corridor (approximately). Will have to keep a close eye on surface temperatures and see how cold air damming is verifying. Right now I think that the immediate coast gets a brief period of snow/sleet/ice and then changes to plain rain. Also, somewhat lighter precipitation amounts here may also result in less of an ability for near-surface temperatures to cool. In a marginal setup, heavier precipitation can help result in more freezing/frozen precipitation.
  12. Quincy
    Generally light snow overspread Connecticut from west to east during the morning on January 28th. Snow continued into the early afternoon and at the same time, warmer air moved in aloft. A change to sleet and freezing rain occurred from southwest to northeast, with portions of the I-95 corridor changing over to plain rain.
    Precipitation tapered off to intermittent drizzle with freezing drizzle across much of the interior by early evening.
    Snowfall totals were fairly uniform with most areas picking up 1 to 2 inches. The I-95 to I-395 corridor and points southeast generally received less than 1 inch of snow. A quicker changeover in lower Fairfield County may have also led to slightly lower snowfall amounts. Some of the hilly terrain of northwestern Connecticut picked up a little more than 2 inches of snow.
    I usually do color contoured maps as well, but I'm not sure it's really necessary for a relatively minor event.
    If you have any totals to add or ones that don't match up, please let me know. Sources include this forum, the National Weather Service, social media reports, WXedge.com, the Conn. Dept. of Transportation and CoCoRaHS.
  13. Quincy
    I just want to quickly share my latest thoughts for Connecticut and surrounding areas.
    There's little doubt that a strong storm with plenty of precipitation will impact the tri-state area and southern New England Friday into early Saturday, but there are still a few details to discuss.
    Concern #1:
    Mixing along the shoreline. An initially "warm" boundary layer may cause mixed precipitation to fall near the Connecticut shoreline and coastal Rhode Island for several hours. With that said, as low pressure really intensifies southeast of Cape Cod, winds shift to the north and cold air pours on down. This will suddenly change everyone back to snow, even across eastern Long Island.
    Concern? Well, right now I have a wide range of 6 to 12 inches in the forecast. I'm leaning on the higher end of those numbers for coastal sections of Conn. and R.I., but there's still some room for change. These numbers could go higher, although I really doubt they'd trend lower...
    Concern #2:
    Deformation band of intense snowfall. These bands can be difficult to predict with accuracy and a slight shift could be the difference between 8 inches and 18 inches. With that said, I expect this band to impact the eastern half of Conn., especially areas like Tolland, Union and Woodstock that stay all snow and hang onto precipitation the longest. In that band, I am predicting more than 20 inches of snowfall.
    Bottom line...heavy snow, strong winds and coastal flooding are likely. I can see widespread blizzard conditions verifying for IJD, ORH, BOS and surrounding areas. (many areas not included in this map, such as northeastern Mass. and southern N.H.
  14. Quincy
    I expect mostly snow for just about all of southern New England (pictured on this map). Although there may be a brief mixture along the I-95 corridor in Conn./RI, I expect crashing temperatures and heights to bring a wind-driven snow right down to the coast and into eastern Long Island.
    As far as snowfall totals go, I think that higher ratios will help push NW Conn. and W Mass. to 20"+. Further east, heavy precipitation will offset somewhat lower ratios for 20"+ from IJD to BOS. There is still some uncertainty with areas further south on this map, such as NYC, BDR, GON...lower ratios and possible mixing don't give me enough confidence to go with higher snowfall amounts. With that said, I could see a scenario where even the Conn. coast gets 20". The Euro is basically a 15-25"+ event region-wide and this model has been outstanding with overall consistency in this forecast.
    Bands of heavy snow are expected to form and some orographic enhancement may bring this heavy snow right back into the higher terrain of western Conn. and the Berkshires. A snow-shadow effect may limit totals somewhat in the Conn. River Valley, but even there I think totals will come close to 20". Potential exists for 2+ feet, especially across central and eastern Massachusetts.
    The other story is the strong winds and power outages are a real concern along and SE of I-95. I think drier snow and somewhat lighter winds inland will limit power issues there.
    What really captures my interest here is that expansive moisture field aloft. Past storms, like Feb. 2006, for example, had a relatively narrow area of moisture. This was able to produce intense banding and 20-30" totals from NYC into W Conn. However, with this storm, the moisture field backs into most of NY and covers just about all of New England. The end result is several bands of heavy snow, perhaps even a "mega" band. Snowfall rates of 2-3" per hour will be likely for several hours and convection/isolated thunder is possible.
    Winds may gust to 50 MPH along and NW of I-95, with higher gusts to the east. I think we'll see many stations verify official blizzard conditions and Cape Cod/Islands could see hurricane force wind gusts.
  15. Quincy
    What a challenging forecast and I still think the models have more to resolve, mainly on Sunday with respect to enhancement of snow along a trough.
    Essentially, a light mixture of rain and snow overspreads the region through later today. Across the lower Hudson Valley, Connecticut, Rhode Island and southeastern Massachusetts, I expect virtually no daytime snow accumulation. Low pressure develops south of the area tonight, but the heaviest precipitation and best lift also stays south.
    Some snow falls early Sunday morning and a period of light to moderate snow may develop for a good chunk of the second half of the day, especially across northern Massachusetts and central New England. Here, snowfall totals are forecast to finish in the 4 to 8 inch range by 12:00 a.m. Monday. (Could snow possibly linger later? Yes.)
    We'll see how things continue to change!
  16. Quincy
    Outside of the hilly terrain across the interior, this snow event does not look like a big deal. I expect 3-6"+ across the east slopes of the Berkshires and much of Worcester County. Connecticut only sees a brief period of rain, with generally 1-3" across the northern hills.
    The boundary layer temperatures are simply too marginal for much to change, especially with dew-points in the upper 20's as of early Tuesday evening. Downstream observations don't indicate that cold air damming across New England will verify stronger than modeled.
  17. Quincy
    Just a very brief discussion:
    Low pressure slowly moves east of the mid-Atlantic coast Wednesday night into Thursday. A relatively broad storm with possible multiple low centers spin around and pinwheel periods of snow (some rain mixing in at the coastal plain) through the region from Wednesday into Friday.
    This looks to be an elevation-dependent event, but heavy amounts or precipitation across eastern Mass., eastern Conn. and much of R.I. will help offset some of the "snow losses." In those areas, 1 to perhaps 2" liquid equivalent precipitation could still result in a solid 5-10, perhaps 12" heavy, wet snowfall. The highest risk for 12" would probably be in southern Worcester County.
    Power outages are a concern, especially in southern and eastern areas. There, the water content will be higher and stronger winds are expected.
    Forecast confidence is moderate...the shoreline and southeastern Mass. could see an even sharper gradient. The banding nature of snow and timing with respect to day vs. night will be crucial in determining snowfall amounts. The snowfall totals above are cumulative, so a total of 10" may actually result in a snow-depth of 7" (for example) by midday Friday.
    The computer models are in decent agreement, although the GFS is a lot more conservative than all other guidance. I feel the GFS has had issues with this storm, despite originally bringing it back when the other models were keeping it south. Recall that the GFS backed off on the blizzard the day it started and totals were close to double what it had predicted.
  18. Quincy
    I don't really expect much snowfall at all tonight. For some continuity and a slight amount of uncertainty, I painted the entire area with 2" or less of snow. Eastern Conn. and northern R.I. have perhaps a 50/50 shot at 1-2": of snow, while the rest of the area has a high probability of receiving less than 1".
    Temperatures and moisture look very marginal and although some precipitation should back southern sections of southern New England, I don't see it being a big deal. There may be a few slushy roads for the Thursday morning commute.
    I don't think it's fair to make a total snowfall map for both events. The coastal plain should rise several degrees above freezing during the day on Thursday with most inland areas also cracking 32F. Also, western areas that may see no accumulation at all tonight could easily end up with some of the higher amounts tomorrow night.

    The snow Thursday night into Friday morning ("Round 2") looks a bit more significant. It gets tricky nailing down enhanced snow along an inverted trough across eastern N.Y. and western New England. At the same time, precipitation closer to a center of low pressure well south of Cape Cod may bring a period of snow to northeastern Conn., northern R.I. and interior eastern Mass. Here, it's a big question mark where totals could verify either low or high. The computer models are having issues nailing down precipitation totals, while some say widespread amounts over 6" could be realized in my eastern 3-6" zone. I don't see it happening, but take that for what it's worth.
    The confidence for the latter forecast is only moderate, but this will be my last snowfall map for the period. Confidence is higher for the first round.
  19. Quincy
    Here are some maps that I compiled from various sources. Most of the reports came in through the National Weather Service, with a few from this forum and social media reports that passed through quality control.
    Snowfall amounts were greatest across the higher terrain of Tolland County. This was due to a persistent band of moderate to heavy snow, as well as the altitude as temperatures were marginal through a portion of the event.
    Totals in the Connecticut River valley and the immediate shoreline were generally lower than surrounding areas. If any amounts you reported conflict with these amounts, please comment back with your total(s).
    Here is an alternate black and white version of the map:

  20. Quincy
    A strong low pressure system is forecast to move up into the Great Lakes by Thursday and eventually into southeastern Canada late Friday into Saturday. A potent cold front associated with this storm will move towards the Appalachians by the second half of Friday. (For Wednesday and Thursday, severe thunderstorm activity is probable for the Mississippi Valley and portions of the western Ohio River Valley.
    I see a marginal setup for severe storms from Central N.Y. into the middle Appalachians. Even though a strong shortwave and upper level jet is expected to move into New York state and Pennsylvania, there are several factors which will likely limit the severe threat...
    With low-level moisture and clouds, daytime heating will not be maximized along the East Coast. Right now, the areas shown in green can expect gradually steepening lapse rates. However, dew-points are only expected to be in the mid-50's to around 60 north of Washington D.C., along with 2-meter temperatures in the mid-60's to lower 70's. eastern Pennsylvania and New Jersey could get well into the 70's, but with the front lagging further to the west, there really isn't much of a trigger to kick off any storms in that area. The SREF/NAM/GFS/Euro are actually fairly similar in timing and overall evolution of this storm system.
    Without much heating, relatively low CAPE values are forecast. The SPC SREF does show a ribbon of slightly negative (0 to -2) Lifted Index values from central Pennsylvania southward. This indicates a marginally unstable atmosphere. As one goes further south into Virginia, the severe weather indices increase, including dew-points into the 60's. This is why that area is outlined in a "low" threat potential.
    Wind shear values are a bit more supportive for severe weather, but even here, the storm system loses some of its punch as it reaches the Appalachian mountains. Effective bulk shear of 40-45kts is forecast across the region. Some strong winds aloft are expected with the front, but this area of stronger winds lags far enough back to really minimize the severe weather threat.
    Overall threats...
    -Damaging wind gusts could be supported anywhere in the green or yellow shadings.
    -In the yellow shading, there's a very slight risk of hail and isolated tornadoes.
    -In New England, gusty winds are possible with a band of rain and thunderstorms late Friday night into early Saturday, but damaging winds are not terribly likely.
    As the spring season goes forward, I will be making more severe weather outlooks. Any feedback is appreciated and I am still working on the outlook/threat scale. I would like to compare forecasts to verification in the future, so some thought will be needed to address just how best to do so. Learning is an ongoing process as I learned a lot about severe weather forecasting last spring/summer and there's still a lot more to cover. Experience also helps!
  21. Quincy
    A strong cold front approaches the Appalachians Friday afternoon and evening. Along that cold front, a squall line with thunderstorms is currently expected is develop.
    (Marginal threat)
    Middle Appalachians into Pennsylvania, northwestern New Jersey and interior New York:
    Daytime heating is expected to push temperatures into the low to mid-70's in the valley locations with mid to upper 60's in the higher elevations. Low and mid-level clouds will likely limit just how unstable the atmosphere can get. As a result, relatively low SBCAPE below 500 J/KG combined with near-zero or marginally negative Lifted Index values are expected. Despite strong winds aloft and effective bulk shear values increasing to 35 to 50kts along a cold front, the lack of instability will likely minimize the threat of severe weather. In addition, dew-points are forecast to stay in the 50's, perhaps coming close to 60° in Maryland and eastern Pennsylvania.
    However, a few isolated strong thunderstorms could develop Friday afternoon ahead of a cold front. There is a marginal threat of a few damaging wind gusts associated with a squall line along the cold front Friday afternoon into Friday night.
    (Low threat)
    Interior Virginia, east of the Appalachians:
    The atmosphere is likely to become slightly more unstable further south. SBCAPE values of 500 to 750 J/KG are forecast based off of SREF guidance. Lifted Index values as low as -3 combined with dew-points in the 60's and higher helicity values would support more strong to severe thunderstorm activity.
    Based off of this, there is a low threat of severe thunderstorms with damaging winds and large hail in this area. Some isolated thunderstorm cells are possible Friday afternoon, but locally severe storms could develop along a squall line Friday night as the cold front approaches.
    There is a marginal threat for an isolated tornado or two, but confidence in this potential is not particularly high at this point.
    (No appreciable severe weather threat)
    Connecticut (southern new England), NYC, Long Island and coastal plain of NJ/DE:
    With more of a marine influence allowing for less daytime heating, there is no appreciable threat of severe weather in these areas. Also, with the cold front not expected to move through until after midnight Friday (into early Saturday), this further implies that the severe weather threat is virtually non-existent.
    With that said, some locally strong wind gusts are possible as a decaying squall line and associated cold front moves through late Friday night into early Saturday morning.
    As the spring season goes forward, I will be making more severe weather outlooks. Any feedback is appreciated and I am still working on the outlook/threat scale. I would like to compare forecasts to verification in the future, so some thought will be needed to address just how best to do so. Learning is an ongoing process as I learned a lot about severe weather forecasting last spring/summer and there's still a lot more to cover. Experience also helps!
  22. Quincy
    The National Weather Service (NWS) confirmed that an EF-1 tornado touched down in New York state Friday evening, shortly before 8 p.m.
    A strong cold front moved across Pennsylvania and New York state late Friday evening. At the same time, a marginally unstable air-mass was in place closer to the surface. With moderate to strong wind shear in place and significant storm relative helicity in place, the stage was set for damaging winds and even a marginal tornado threat.
    As a result, a Tornado Watch for a large portion of Pennsylvania and New York state. A tornado touched down near Bainbridge, N.Y. in Chenango County and stayed on the ground for 3.2 miles. The tornado was a strong EF-1 with maximum sustained winds of 110 MPH.
    Looking back at historical tornado environments in the same general area, the wind shear and helicity values in place on Friday were actually more "severe" than the climatological mean for past tornadoes. The only thing that was lacking was instability, as there was very little in place. Despite this fact, strong, twisting and turning winds aloft combined with an approaching squall line ahead of a cold front resulted in the tornado.
    PUBLIC INFORMATION STATEMENT...UPDATED
    NATIONAL WEATHER SERVICE BINGHAMTON, NY
    954 AM EDT MON APR 22 2013
    ...TORNADO CONFIRMED FROM 4 SSE BAINBRIDGE IN CHENANGO COUNTY TO 3 S SIDNEY IN DELAWARE COUNTY NEW YORK...
    UPDATED DATA ON LAT/LON POINTS AND WIDTH.
    LOCATION...
    FROM 4 SSE BAINBRIDGE IN CHENANGO COUNTY TO 3 S SIDNEY IN DELAWARE COUNTY NEW YORK
    DATE...APRIL 19 2013
    ESTIMATED TIME...753 PM TO 758 PM EDT
    MAXIMUM EF-SCALE RATING...EF1
    ESTIMATED MAXIMUM WIND SPEED...110 MPH
    MAXIMUM PATH WIDTH...200 YARDS
    YARDS PATH LENGTH...3.2 MILES
    BEGINNING LAT/LON...42.2481N / 75.4516W
    ENDING LAT/LON...42.2674N / 75.3939W
    * FATALITIES...0
    * INJURIES...0
    * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS STORM DATA.
    ..SUMMARY
    THE NATIONAL WEATHER SERVICE IN BINGHAMTON, NY HAS CONFIRMED THAT A TORNADO TOUCHED DOWN ABOUT 4 MILES SSE OF BAINBRIDGE IN CHENANGO COUNTY...TRACKED NORTHEAST ABOUT 3.2 MILES...AND THEN ENDED ABOUT 3 MILES SOUTH OF SIDNEY IN DELAWARE COUNTY NEW YORK FROM 753 PM EDT TO 758 PM EDT ON APRIL 19 2013.
    THE TORNADO TOUCHED DOWN BETWEEN INTERSTATE 88 AND HIGHWAY 206...ON EAST AFTON ROAD...WHERE 2 POWER POLES WERE SNAPPED AND A CAR WAS DESTROYED BY A LARGE TREE BRANCH. ANOTHER VEHICLE WAS ALSO DAMAGED. SEVERAL TREES WERE SNAPPED OR UPROOTED. A BARN HAD MINOR ROOF DAMAGE. THE TORNADO CONTINUED NORTHEAST AND CROSSED HIGHWAY 206...WHERE A FARM EQUIPMENT BUILDING AND A MOBILE HOME WERE HEAVILY DAMAGED...AND A STORAGE TRAILER WAS DESTROYED. OTHER NEARBY HOMES HAD MINOR DAMAGE...AND A CARPORT WAS LIFTED AND MOVED 75 FEETFARTHER DOWN ITS PATH...THE TORNADO INTENSIFIED TO A HIGH END EF1 STRENGTH WHILE TRAVELING IN THE VICINITY OF HOUCK DRIVE. IN THIS AREA IT UPROOTED OR SNAPPED MANY 1 TO 2 FOOT DIAMETER TREES ALONG ITS PATH...BOTH HARDWOODS /MAPLES/ AND SOFTWOODS /PINES/...WITH THE LARGEST MORE THAN 3 FEET WIDE. IT ALSO CAUSED STRUCTURAL DAMAGE TO A SINGLE FAMILY RESIDENCE AND GARAGE...WHILE TRANSPORTING A SIGNIFICANT AMOUNT OF DEBRIS A HUNDRED YARDS OR MORE. THE TORNADO THEN CROSSED INTO DELAWARE COUNTY...DOWNING SEVERAL MORE TREES ON SOME PROPERTIES ALONG HIGHWAY 8 BEFORE DISSIPATING.
    Here's an SPC archived radar image from 00z, just minutes after the tornado touched down. A noticeable kink can be seen along the squall line near the location of the tornado, along with the approximate track below it:


    Here are some more storm reports from Friday:


  23. Quincy
    A cold front is forecast to move from west to east across the East Coast on Wednesday. The result could mean scattered thunderstorms along the front, along with a few severe thunderstorms.
    (Marginal threat)
    Middle Appalachians into DE, PA, inland NJ and interior NY.
    A similar setup to this past Friday is expected on Wednesday, with a cold front moving across the area during the afternoon and evening hours. The only difference here is that the cold front is not as strong as that scenario (last Friday) and less convective activity is expected.
    Ahead of the cold front, some marginal destabilization is expected as near-surface temperatures rise into the 70's, slightly steepening lapse rates. As a result, Lifted Index values between 0 and -2 are forecast. MUCAPE is meager, with values generally less than 500 J/Kg. Although dew-points are forecast to be in the mid to upper 50's, wind shear and helicity is forecast to be somewhat less than the last event. Bulk shear of 30 to 50kt is forecast across eastern Pennsylvania, coupled with storm relative helicity values of 100-200, so some isolated damaging wind gusts are possible.
    (Low threat)
    Interior Virginia, Central Maryland and portions of eastern Pennsylvania.
    In this region, the timing of the cold front corresponds closely with the peak daytime heating. There's also a sliver of 500 to 1000 J/Kg CAPE values expected in south-central Pennsylvania, down into Maryland and Virginia. It's also in this general area that there is a marginal tornado threat, however the tornadic setup on Wednesday is also less impressive than it was last Friday.
    Graphics to differentiate between the damaging wind and tornado threats:

    (No appreciable severe weather threat)
    Southern New England, Long Island and coastal plain of New Jersey.
    The cold front does not make it into this area until midnight or a few hours afterward. At that time, moisture is very limited, wind shear values relax and there should be little to no instability to fuel thunderstorm activity.
    Threat definitions...(Severe thunderstorm = wind gusts to 58 MPH and/or >1" hail)
    Marginal: Conditions are marginally favorable for severe thunderstorms.
    Low: Conditions are somewhat favorable for severe thunderstorms.
    Moderate: Conditions are moderately favorable for severe thunderstorms.
    High: Conditions are very favorable for severe thunderstorms.
    Extreme: Conditions are extremely favorable and dangerous thunderstorms are likely.
    As the spring season goes forward, I will be making more severe weather outlooks. Any feedback is appreciated and I am still working on the outlook/threat scale. I would like to compare forecasts to verification in the future, so some thought will be needed to address just how best to do so.
    *Disclaimer* The intent here is somewhat different than SPC severe weather outlooks. The green, yellow, etc. shadings do not directly correlate between SPC and my own outlooks. I'm still getting a feel for these outlooks, but I imagine that in more impressive severe setups, I will use red and orange colors a bit more generously than SPC might. Also, green colors on my maps indicate a marginal severe weather threat, while on SPC it corresponds to a general thunderstorm (not necessarily severe) threat.
  24. Quincy
    I've been creating daily 6-day forecasts for the better part of this year, with a focus on inland Connecticut. Before making any forecast, I take a close look at the computer model forecasts through Day 6, including a few forecast techniques to see how verification pans out. In April, I had 29 days worth of data, out of a possible 30, to measure forecast accuracy.
    As expected, forecast error generally increases with time. It is interesting to note a spike at Day 5 and a decrease at Day 6. That goes back to two particular days that had poor Day 5 forecasts vs. actual temperatures. The spread is relatively uniform as well. The error with the NAM model does seem to increase faster with time than the others, which is not a surprise. DGEX data was used for Days 5 and 6.
    With respect to my own forecasts, I measure verification as a mean of inland temperatures across the state. When I look at the computer models, I choose Meriden (KMMK) as a central point. This is due to its location near the center of the state. With that said, since my own verification is slightly different than the control (KMMK), this may skew results slightly. For that reason, I will be creating 6-day forecasts specifically for Meriden as a go-forward.
    The Euro and MAV MOS rank fairly close, but it is very interesting to note that the negative (cold) bias the Euro has is almost a mirror reflection of the MAV MOS positive (warm) bias:

    The MAV MOS appears to correct some of its bias towards Days 5 and 6. That can perhaps be partially explained by the fact that MOS is skewed towards climatological temperatures. The NAM also seems to have somewhat of a cool bias. I re-project highs from the NAM for Day 1, but that re-projection seems to over compensate the bias, at least in the case of April.
    Explaining the models/forecasts...
    Q: My forecast high temperatures for inland Connecticut. (mean of inland stations)
    MAV MOS: Forecast high temperatures for KMMK. (06z model run)
    ECMWF: Forecast grid-point high temperatures for KMMK. (00z model run)
    NAMDGEX: Approximate high temperatures for KMMK. These values are interpolated off of a graphical forecast, so the numbers are estimated. I use the NAM for Days 1-4 and the DGEX for Days 5 and 6. (06z model runs)
    850mb: An 850mb forecast technique that I have been working on for quite some time. Because this technique is based off of Danbury (KDXR), that station is used for verification.
    LAMP MOS: Forecast high temperatures for KMMK. (most recent run in morning)
    NAM Re-projection: This takes into account the actual 9 a.m. temperature vs. the 06z forecast for 9 a.m. for KMMK. That error is then re-projected into the high temperature forecast. Example: If the 9 a.m. temperature was 2°F warmer than forecast, then 2°F is added to the high temperature forecast.
    Consensus: A mean of each forecast above, including my previous forecast (continuity)
    How accurate was a Euro/MAV MOS blend? Well, not only do the opposing biases balance out close to zero, but the overall forecast error was less than any other forecast technique for Days 2-6:

    It's pretty interesting to see the results. It goes beyond comparing computer model verification. In order to become a better forecaster, I want to see what forecasts have worked out, which ones haven't and if I have any biases. This is only one month's worth of data, so more will need to be compiled over the long-run to see how models perform. I also expect that different models/techniques will perform differently depending on the season, weather pattern, etc.
  25. Quincy
    As a cold front moves towards the East Coast on Saturday, some thunderstorm development is possible during the afternoon and early evening hours.
    Low threat (Conditions are somewhat favorable for severe thunderstorms)
    Mid-Atlantic region (east of Appalachians), lower Hudson Valley and SW New England.
    Conditions will destabilize in a warm, somewhat moist air-mass before an approaching cold front swings from west to east through the area. The biggest question mark is how much daytime heating will take place. Across Virginia, there will likely be more heating and with higher dew-points here as well, in the mid-60's, some thunderstorm development is likely. Some of these storms could reach severe limits.
    Further north, across eastern Pennsylvania, interior New Jersey, southeastern New York, northwestern Connecticut and the Berkshires, the threat of severe thunderstorm activity relies heavily upon daytime heating. The NAM continues to show some scattered showers and mid-level moisture limiting the destabilization process. With that said, the SREF/NAM/GFS still show a narrow finger of somewhat unstable air in this region. CAPE values between 250-500 J/kg, LI values around -2 and bulk shear around 30kt could result in a few thunderstorms reaching severe limits. Dew-points are progged to reach the lower 60's by the NAM. The 18z NAM simulated radar shows a squall line developing from Baltimore to Philadelphia to Poughkeepsie. However, this line is relatively short-lived as it collapses upon reaching the coastal plain and western Connecticut.
    It should be noted that helicity values increase towards the northeast, especially in New England. This may work to offset the slightly less unstable atmosphere.
    Bottom line, some thunderstorms may produce damaging winds from the mid-Atlantic region into southwestern New England. Some hail is possible here, but there's a stronger potential for severe hail further south.
    The tornado risk is relatively low, although Significant Tornado Parameter (STP) values indicate that a brief tornado or two could form anywhere in the yellow shading. Local topography across the Appalachians could aid in some rotation with any cells. When running the numbers, the tornado parameters are a bit below the mean tornado environments for historic tornadoes in the region, but are higher than what verified on Thursday with the brief EF-0 tornado in eastern Massachusetts.
    A few renegade thunderstorm cells could fire ahead of a cold front Saturday afternoon, especially across Virginia, where there may be a few supercells. A squall line along the cold front is more likely, advancing through eastern Pennsylvania early in the afternoon and towards the NYC metropolitan area and the coastal plain by mid to late afternoon. Instability will be key in the formation of and ability of this line to maintain itself.
    Marginal threat (Conditions are marginally favorable for severe thunderstorms)
    Mid and upper Appalachians and portions of southern New England.
    Shower and thunderstorm activity is likely across the entire area, but less daytime heating will limit the severe weather threat. As one moves eastward, especially towards the coastal plain of New England, the threat decreases significantly.
    Threat definitions...(Severe thunderstorm = wind gusts to 58 MPH and/or >1" hail)
    Marginal: Conditions are marginally favorable for severe thunderstorms.
    Low: Conditions are somewhat favorable for severe thunderstorms.
    Moderate: Conditions are moderately favorable for severe thunderstorms.
    High: Conditions are very favorable for severe thunderstorms.
    Extreme: Conditions are extremely favorable and dangerous thunderstorms are likely.
    *Disclaimer* The intent here is somewhat different than SPC severe weather outlooks. The green, yellow, etc. shadings do not directly correlate between SPC and my own outlooks. I'm still getting a feel for these outlooks, but I imagine that in more impressive severe setups, I will use red and orange colors a bit more generously than SPC might. Also, green colors on my maps indicate a marginal severe weather threat, while on SPC it corresponds to a general thunderstorm (not necessarily severe) threat.

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