donsutherland1

Morning thoughts... A major to perhaps borderline historic snowstorm (top 20 or above) will affect the region over the next several days. At 6:45 am, snow was falling in Washington, DC and parts of nearby Maryland. That snow will move into Baltimore early this morning and Philadelphia later this morning or early this afternoon. Clouds will increase and snow will push in Newark and New York City late this afternoon or perhaps early this evening. Snow will fall at varying intensities overnight. Temperatures will top out in the upper 20s and lower 30s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 28° Newark: 29° Philadelphia: 32° As the secondary storm develops and then wanders near the Middle Atlantic coastline, blizzard conditions are possible in parts of the northern Mid-Atlantic region tomorrow into tomorrow night. An area running from eastern Pennsylvania through the New York City Metro area and across Nassau County could see some of the storm’s highest snowfall totals with embedded figures approaching or reaching two feet. Estimated snowfall totals: Allentown: 16”-24” Boston: 5”-10” Bridgeport: 12”-18” Islip: 8”-16” New York City: 14”-20” Newark: 14”-20” Philadelphia: 7”-14” Poughkeepsie: 8”-16” This storm will very likely join the 10 one-foot or larger snowstorms that have blanketed New York City since 2000. Six of those storms dumped 18” or more snow. Those 10 storms were: December 30, 2000: 12.0” February 16-17, 2003: 19.8” December 5-7, 2003: 14.0” January 22-23, 2005: 13.8” February 11-12, 2006: 26.9” February 25-26, 2010: 20.9” December 26-27, 2010: 20.0” January 26-27, 2011: 19.0” February 13-14, 2014: 12.5” January 22-24, 2016: 27.5”

The overnight guidance (UKMET excluded) was great.

And Morgantown, PA picked up 50” snow.

The NAM’s focus of heaviest snows closely resembles earlier cycles of the GFSv16.

A storm will move into the Ohio Valley tomorrow with secondary development taking place off the Middle Atlantic coast. As a result, much of the region will experience its biggest snowfall since at least December 16-17, 2020. At present, much of the region appears to be in line for a significant to potentially major snowfall from late Sunday through Tuesday. There will be widespread amounts of 6" or above in the Middle Atlantic and southern New England areas. There will also be a swath of 12" or greater snowfall, but details concerning the location of the heaviest snow still remain somewhat uncertain. Enough warmer air could come in off the Atlantic Ocean to change the snow to mixed precipitation or rain along New Jersey's south shore, parts of Long Island and southeastern New England (Cape Cod and Nantucket). Some of the guidance even brings the mixing into New York City. Initial snowfall estimates: Boston: 5"-10" Bridgeport: 7"-14" Islip: 6"-12" New York City: 7"-14" Newark: 8"-16" Philadelphia: 6"-12" Poughkeepsie: 5"-10" The GFSv16 is more aggressive with snowfall amounts across New York City and Long Island. In contrast, the National Blend of Models shows at least a 40% probability of rain in New York City Tuesday morning, which results in a lower accumulation figure than seen on much of the individual guidance. The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.1°C for the week centered around January 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.85°C and the ENSO Region 3.4 anomaly has averaged -1.07°C. La Niña conditions will likely prevail at least through meteorological winter. The SOI was +6.65 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.904. On January 29 the MJO was in Phase 6 at an amplitude of 2.436 (RMM). The January 28-adjusted amplitude was 2.281. Following a significant stratospheric warming event, the stratosphere has continued to cool. Based on the latest guidance, no significant stratospheric warming event is likely into the first week of February. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 34.8°.

Morning thoughts... Today will be fair but continued unseasonably cold. In spite of bright sunshine, temperatures will likely top out in the upper 20s and lower 30s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 29° Newark: 31° Philadelphia: 33° A significant to potentially major snowstorm is likely in the northern Middle Atlantic and southern New England regions late Sunday through Tuesday.

At New York City, the temperature fell to 14°. That was Central Park's coldest reading since February 15, 2020 when the temperature fell to 14°. At Boston, the temperature fell to 7°. That was Boston's coldest temperature since January 31, 2019 when the mercury dipped to 5°. Select low temperatures in the Northeast included: Albany: 0° Allentown: 17° Boston: 7° Bridgeport: 12° Burlington: 2° Concord: 4° Hartford: 6° Islip: 15° New York City: 14° Newark: 16° Philadelphia: 23° Portland: 10° Poughkeepsie: 11° Providence: 9° White Plains: 11° Worcester: 2° Following another very cold night, tomorrow will be a cold but dry day. Temperatures will likely reach only the upper 20s in much of the region with some lower 30s near or around Philadelphia and southern New Jersey. Afterward, the pieces will likely come together for the region's biggest snowfall since at least December 16-17, 2020. The potential currently exists for a significant (6" or greater) snowfall in parts of the Middle Atlantic and southern New England regions from late Sunday through Tuesday. An area of totals of 1 foot or more is likely, but details remain to be resolved. The EPS ensemble forecast 500 mb pattern in eastern North America is somewhat similar to that on January 30, 1966 except that the trough is modeled somewhat to the south of where it was then. The January 29-31, 1966 storm brought a widespread 6" or more snowfall from Washington, DC to Boston. In short, the forecast pattern suggests potential and it is similar to one case where the snowfall potential was realized. Nevertheless, one should not use the 1966 case to infer largely identical outcomes. The evolution of the storm will determine where the heaviest snows fall and how much snow falls. The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.1°C for the week centered around January 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.85°C and the ENSO Region 3.4 anomaly has averaged -1.07°C. La Niña conditions will likely prevail at least through meteorological winter. The SOI was +8.91 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.458. On January 28 the MJO was in Phase 6 at an amplitude of 2.272 (RMM). The January 27-adjusted amplitude was 1.908. Following a significant stratospheric warming event, the stratosphere has continued to cool. Based on the latest guidance, no significant stratospheric warming event is likely into the first week of February. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 34.7°.

One should not use the 1966 blizzard to draw conclusions about the upcoming event. I mentioned it just to illustrate that reasonably similar 500 mb patterns in eastern North America have produced big storms before. The 1966 storm brought 6” or more snow from North Carolina to southern New England. It also triggered lake effect snow around its strong circulation. Some accumulations: Boston: 6.3”; New York City: 6.8”; Philadelphia: 8.3”; and, Washington, DC: 13.8”. New York City changed over to rain as the storm tracked northward just to its west. Where lake effect snow was involved, Rochester received 26.7” and Syracuse picked up 39.0”. Unlike the upcoming storm, the 1966 storm developed along an advancing Arctic front.

Morning thoughts... The coldest air so far this season now covers the region. At 7 am, the temperature in Central Park was 16°. That is New York city’s first reading in the teens since February 15, 2020 when the temperature fell to 14°. Winter 2019-20 had 3 days on which the temperature fell below 20° in New York City. Winter 2018-19 had 11 such days. Despite sunshine, temperatures will likely top out in the lower and middle 20s in most of the region. Areas near Philadelphia could rise into the upper 20s or perhaps lower 30s. Likely high temperatures around the region include: New York City (Central Park): 24° Newark: 25° Philadelphia: 30° A significant snowfall is possible early next week. The 0z GFS and GDPS, along with the 6z GFS favor a significant snowfall. Through 84 hours, both the NAM and RGEM are reasonably in line with the guidance showing a significant snowfall. However, this outcome is not yet cast in stone. The 0z ECMWF is an outlier with a more offshore solution. The percentage of EPS ensemble members showing 6” or more snow for the Philadelphia to Boston area has decreased from 1/28 0z and 12z.

Seasonal snowfall amounts to date include: Albany: 39.5" (6.4" above normal) Baltimore: 2.1" (7.2" below normal) Binghamton: 65.1" (21.0" above normal) Boston: 23.1" (1.1" above normal) Bridgeport: 13.0" (0.3" above normal) Buffalo: 42.0" (17.3" below normal) Burlington: 34.1" (8.3" below normal) Caribou: 44.7" (13.2" below normal) Harrisburg: 11.7" (1.4" below normal) Islip: 7.8" (4.1" below normal) New York City: 10.6" (0.7" below normal) Newark: 12.9" (0.1" above normal) Philadelphia: 6.6" (2.7" below normal) Portland: 25.2" (7.4" below normal) Providence: 15.0" (3.3" below normal) Washington, DC: 0.3" (7.4" below normal) Many of those locations will likely see additions to these figures within the next week. The coldest air mass so far this season is now pushing into the region. As a result, tomorrow and possibly Saturday could see high temperatures only in the lower and middle 20s in much of the region. Central Park will very likely see its first teens of the season overnight tonight. The ensembles suggest that the PNA could approach positive levels or even go positive near the end of the month into the start of February. That could allow for the potential of a snow event during the February 1-2 period before milder air returns during the first week of February. At present, the potential currently exists for a significant (6" or greater) snowfall in some parts of the Middle Atlantic and/or southern New England regions. The EPS ensemble forecast 500 mb pattern in eastern North America is somewhat similar to that on January 30, 1966 except that the trough is modeled somewhat to the south of where it was then. The January 29-31, 1966 storm brought a widespread 6" or more snowfall from Washington, DC to Boston. In short, the forecast pattern suggests potential and it is similar to one case where the snowfall potential was realized. Nevertheless, one should not use the 1966 case to infer largely identical outcomes. The evolution of the storm will determine where the heaviest snows fall and how much snow falls. The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.1°C for the week centered around January 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.85°C and the ENSO Region 3.4 anomaly has averaged -1.07°C. La Niña conditions will likely prevail at least through meteorological winter. The SOI was +21.11 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.601. On January 27 the MJO was in Phase 6 at an amplitude of 1.903 (RMM). The January 26-adjusted amplitude was 1.736. Following a significant stratospheric warming event, the stratosphere has continued to cool. Based on the latest guidance, no significant stratospheric warming event is likely into the first week of February. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 34.7°.

While Phase 7 (amplitude 1.000 or above) is typically very warm in February (mean temperature of 43.4° in New York City for the February 1-29, 1974-2020 period), it is somewhat cooler when the AO is at or below -1.000 (41.0°). However, there have been exceptions. Early February 1978, which culminated in a major blizzard was one such case. One long-duration event was February 1-10, 1993. There was a lot of variation in daily temperatures, but the mean temperature was 31.6°. There were also three days on which the temperature fell into single digits (February 1-2, 7). The coldest temperature was 7°, on February 2 and February 7. March 1993 saw a major East Coast snowstorm. Just as one has witnessed competing factors that have precluded a canonical La Niña response to date, despite the La Niña's relative stability at moderate levels), there could be factors that delay or even limit the magnitude of warming should the MJO enter a long-duration pause in Phase 7. Having said that, I think the first week of February will turn warmer following the storm on February 1-2. Whether that warmth is sustained is uncertain. Some of the guidance has periodically suggested another fresh shot of cold near the end of the first week of February or just afterward.

About 75%-80% of the precipitation was snow on the 6z soundings. I haven't looked at the 12z soundings, but will check later. Things, of course, can still change given how far the storm is in the future and the complexity involved with Miller B transitions.

It scores high at 500 mb, but it can be often quite volatile with poor run-to-run continuity. The difference between its 1/28 0z and 1/28 12z runs is a case in point. Let’s see what the ECMWF shows.

Morning thoughts... Today will be variably cloudy and cold. A strong cold front will cross the region this afternoon. Some areas could see some flurries or even a burst of snow. Temperatures will likely top out in the lower and middle 30s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 32° Newark: 33° Philadelphia: 34° A significant snowfall is possible early next week. Approximately 75% of the EPS ensemble members from the 1/28 0z run showed 6” or more snow for New York City. GFS soundings suggest that there will be some rain or sleet in the City and that the snow could be fairly wet as temperatures hover around 33° or 34° during much of the storm.

The recent light snow event brought 0.1" snow to New York City's Central Park. However, Boston picked up 4.6" snow. That was the third 4" or greater snow event Boston has seen during winter 2020-21. The last winter with at least three such events was winter 2017-18 when Boston had five such snowfalls. Tomorrow will be fair and colder. The coldest air mass so far this season will begin moving into the region. In its wake, Friday and possibly Saturday could see high temperatures only in the lower and middle 20s in much of the region. Central Park will very likely see its first teens of the season. The ensembles suggest that the PNA could approach positive levels or even go positive near the end of the month into the start of February. That could allow for the potential of a snow event during the February 1-2 period before milder air returns during the first week of February. The EPS ensemble forecast 500 mb pattern in eastern North America is somewhat similar to that on January 30, 1966 except that the trough is modeled somewhat to the south of where it was then. The January 29-31, 1966 storm brought a widespread 6" or more snowfall from Washington, DC to Boston. In short, the forecast pattern suggests potential and it is similar to one case where the snowfall potential was realized. Nevertheless, one should not use the 1966 case to infer largely identical outcomes. The evolution of the storm will determine where the heaviest snows fall and how much snow falls. At present, the potential currently exists for a significant (6" or greater) snowfall in some parts of the Middle Atlantic and/or southern New England regions. The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.1°C for the week centered around January 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.85°C and the ENSO Region 3.4 anomaly has averaged -1.07°C. La Niña conditions will likely prevail at least through meteorological winter. The SOI was +30.39 today. Today, the preliminary Arctic Oscillation (AO) figure was -3.313. On January 26 the MJO was in Phase 6 at an amplitude of 1.734 (RMM). The January 25-adjusted amplitude was 1.891. Following a significant stratospheric warming event, the stratosphere has continued to cool. Based on the latest guidance, no significant stratospheric warming event is likely into the first week of February. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 34.8°.

The forecast discussions explain the National Weather Service’s thinking at present. From Upton’s discussion: LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... The primary focus of the Long Term is the potential storm for the beginning of next week. High pres over Ontario and Quebec over the weekend will funnel arctic air into the region. Temps will be blw normal, with the NBM with local adjustments used for the fcst. The models have been consistent with the potential for low pres impacting the region for the beginning of next week...perhaps for an extended period of time. The GFS has continued this theme, but the 12Z run appears a lot faster than the model consensus has been. The ECMWF is more consistent with a slower timing. The differences are noted with the emergence of the upr low from the Rockies on Sat mrng. The GEM supports the slower ECMWF at H5 early Sat. For these reasons, the fcst leans towards the slower model timing. The GFS wasn`t completely discounted, but pops were limited to slight chance during the day on Sun, which was blw the NBM. In addition to the timing differences, there are also uncertainties with track and intensity. The ECMWF continues to resemble the progs it has been putting out for several runs, and the GFS is echoing this type of soln as well. Both models have a blocking high over the Atlc which will serve to slow the sys. The fcst keeps pops at high chance Mon and Mon ngt. Pops were raised abv the NBM on Tue to the chance category due to increased confidence in a slowing sys. Depending on the exact track, srn and ern areas could see mixing or a changeover to rain by Mon, lasting thru Mon ngt before everything ends as snow. Typical north and west areas mainly snow attm. Using the 12Z runs as perfect progs, the ECMWF would be a lot of rain for the coasts and ern areas with the low slipping inside the benchmark. The GFS would be mainly snow with the low staying s and e of the benchmark.

000 NOUS41 KOKX 271704 PNSOKX CTZ005>012-NJZ002-004-006-103>108-NYZ067>075-078>081-176>179-280504- Public Information Statement Spotter Reports National Weather Service New York NY 1204 PM EST Wed Jan 27 2021 The following are unofficial observations taken during the past 24 hours for the storm that has been affecting our region. Appreciation is extended to highway departments, cooperative observers, Skywarn spotters and media for these reports. This summary also is available on our home page at weather.gov/nyc ********************STORM TOTAL SNOWFALL******************** LOCATION TOTAL TIME/DATE COMMENTS SNOWFALL MEASURED (inches) CONNECTICUT ...Fairfield County... 3 W Danbury 3.0 900 AM 1/27 CoCoRaHS New Fairfield 2.7 600 AM 1/27 Trained Spotter 1 ENE Norwalk 2.0 800 AM 1/27 CoCoRaHS Bethel 2.0 902 AM 1/27 CoCoRaHS 2 ENE New Canaan 1.9 800 AM 1/27 CoCoRaHS Bridgeport Airport 1.6 700 AM 1/27 Official NWS Obs 3 SSE Brookfield 1.5 700 AM 1/27 CoCoRaHS 3 NNW Norwalk 1.5 700 AM 1/27 CoCoRaHS 2 NW Darien 1.5 700 AM 1/27 CoCoRaHS Bethel 1.5 700 AM 1/27 CoCoRaHS 1 W Shelton 1.4 700 AM 1/27 CoCoRaHS 4 NNE Ridgefield 1.3 700 AM 1/27 CoCoRaHS 5 SE Newtown 1.2 800 AM 1/27 CoCoRaHS Darien 1.2 750 AM 1/27 CoCoRaHS Stratford 1.0 600 AM 1/27 CoCoRaHS Old Greenwich 1.0 800 AM 1/27 CoCoRaHS Monroe 1.0 600 AM 1/27 CoCoRaHS 5 SSW Newtown 1.0 700 AM 1/27 CoCoRaHS 4 N Ridgefield 1.0 630 AM 1/27 CoCoRaHS ESE Stratford 1.0 700 AM 1/27 CoCoRaHS ...Middlesex County... 1 SE Middlefield 1.8 700 AM 1/27 CoCoRaHS 3 ESE Killingworth 1.7 700 AM 1/27 CoCoRaHS 1 N Higganum 1.6 800 AM 1/27 CoCoRaHS 1 W Durham 1.5 700 AM 1/27 CoCoRaHS 1 N Killingworth 1.5 700 AM 1/27 CoCoRaHS Clinton 1.1 230 AM 1/27 Broadcast Media ...New Haven County... 2 ENE Prospect 2.5 611 AM 1/27 CoCoRaHS 1 SW Prospect 2.1 800 AM 1/27 CoCoRaHS Milford 2.0 603 AM 1/27 Trained Spotter 4 N Madison Center 2.0 700 AM 1/27 CoCoRaHS 2 W Wallingford 2.0 816 AM 1/27 CoCoRaHS 2 NNE Naugatuck 2.0 700 AM 1/27 CoCoRaHS Guilford 1.9 700 AM 1/27 Co-Op Observer 3 NNW Wallingford Ce 1.8 700 AM 1/27 CoCoRaHS 2 WNW Wallingford Ce 1.7 700 AM 1/27 CoCoRaHS Hamden 1.5 745 AM 1/27 Trained Spotter 3 NNW New Haven 1.1 700 AM 1/27 CoCoRaHS 2 W Madison Center 1.0 700 AM 1/27 CoCoRaHS 2 NE Seymour 1.0 700 AM 1/27 CoCoRaHS 1 SW Northford 1.0 700 AM 1/27 CoCoRaHS ...New London County... 2 SSE Pawcatuck 2.5 700 AM 1/27 CoCoRaHS 3 NNE Norwich 2.1 600 AM 1/27 CoCoRaHS 2 ENE Uncasville-Oxo 2.0 700 AM 1/27 CoCoRaHS 2 SE Norwich 2.0 700 AM 1/27 Co-Op Observer 1 NNE Stonington 2.0 700 AM 1/27 CoCoRaHS 3 WNW Oakdale 2.0 700 AM 1/27 CoCoRaHS 3 SSW Central Waterf 2.0 700 AM 1/27 CoCoRaHS 1 W Mystic 2.0 700 AM 1/27 CoCoRaHS 3 NW Mystic 1.8 700 AM 1/27 CoCoRaHS 1 SW East Lyme 1.7 600 AM 1/27 CoCoRaHS 1 NNW New London 1.6 730 AM 1/27 CoCoRaHS 3 ESE Old Lyme 1.5 700 AM 1/27 CoCoRaHS 1 SW Niantic 1.5 800 AM 1/27 CoCoRaHS NEW JERSEY ...Bergen County... 1 SSE Oakland 2.0 800 AM 1/27 CoCoRaHS 1 W Tenafly 0.8 730 AM 1/27 CoCoRaHS 1 SE Fair Lawn 0.8 653 AM 1/27 CoCoRaHS ...Essex County... 1 N Montclair 0.2 800 AM 1/27 CoCoRaHS ...Hudson County... 2 NW Kearny 0.5 1200 AM 1/27 CoCoRaHS ...Passaic County... 2 ESE Wayne Twp 1.0 800 AM 1/27 CoCoRaHS Wayne 0.9 800 AM 1/27 Trained Spotter 1 WNW Little Falls T 0.8 700 AM 1/27 CoCoRaHS ...Union County... Newark Airport 0.5 700 AM 1/27 FAA Observer 1 ESE New Providence 0.4 730 AM 1/27 CoCoRaHS 1 ENE Clark Twp 0.1 900 AM 1/27 CoCoRaHS NEW YORK ...Nassau County... SSE Albertson 0.5 730 AM 1/27 CoCoRaHS W Floral Park 0.1 700 AM 1/27 CoCoRaHS ...New York County... Central Park 0.1 700 AM 1/27 PARK CONSERVANCY ...Orange County... 1 S Walden 2.4 700 AM 1/27 CoCoRaHS Monroe 2.0 425 AM 1/27 Trained Spotter 1 N Port Jervis 2.0 700 AM 1/27 Co-Op Observer 3 ESE Port Jervis 1.8 630 AM 1/27 CoCoRaHS 1 NNW Cornwall On Hu 1.8 700 AM 1/27 CoCoRaHS 3 WNW Warwick 1.7 700 AM 1/27 CoCoRaHS 3 SW Greenwood Lake 1.0 800 AM 1/27 CoCoRaHS ...Putnam County... Carmel Hamlet 2.0 800 AM 1/27 Co-Op Observer Cold Spring 1.8 721 AM 1/27 CoCoRaHS ...Queens County... NYC/LaGuardia Airpor 0.1 700 AM 1/27 FAA Observer NYC/JFK Airport T 700 AM 1/27 FAA Observer ...Richmond County... 1 SE Staten Island 0.2 700 AM 1/27 CoCoRaHS ...Rockland County... 1 NW Stony Point 1.5 700 AM 1/27 CoCoRaHS ...Suffolk County... Orient Point 0.4 800 AM 1/27 Co-Op Observer SSW Port Jefferson S 0.4 830 AM 1/27 CoCoRaHS Centerport 0.4 700 AM 1/27 Co-Op Observer Riverhead 0.3 800 AM 1/27 CoCoRaHS 1 SSW Nesconset 0.3 857 AM 1/27 CoCoRaHS Baiting Hollow 0.2 824 AM 1/27 Co-Op Observer Upton 0.2 700 AM 1/27 NWS Office Islip Airport 0.1 700 AM 1/27 FAA Observer ...Westchester County... Harrison 2.0 841 AM 1/27 Trained Spotter N Peekskill 1.5 800 AM 1/27 CoCoRaHS SE Armonk 1.5 800 AM 1/27 CoCoRaHS Thornwood 1.5 1050 AM 1/27 CoCoRaHS South Salem 1.1 747 AM 1/27 CoCoRaHS Katonah 1.0 900 AM 1/27 CoCoRaHS Shrub Oak 1.0 645 AM 1/27 Co-Op Observer

The pattern for this event has potential. The GEFS has even more members showing the development of a PNA+ around the time of the storm. Details will need to be worked out, but this should have a much higher impact than anything the region has seen since December 16-17, 2020.

Morning thoughts... In the wake of yesterday’s minor system, today will be variably cloudy and seasonably cold. Temperatures will likely top out in the upper 30s and lower 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 39° Newark: 41° Philadelphia: 42° A more significant snowfall is possible early next week. More than half the EPS ensemble members from the 1/27 0z run showed 6” or more snow for New York City.

Two photos from this morning.

There was a brief burst of snow that whitened the untreated streets and sidewalks in Larchmont, NY just past 9:00 PM.

I haven't really tried to compare the GEFS and EPS per se. However, both have had persistent difficulty beyond a week when it comes to the EPO. I'm not sure about the reason for that.

Since December 1, the Arctic Oscillation (AO) has averaged -1.987. Winter 2020-21 is the 11th winter since 1950-51 where the AO averaged -1.500 or below for the December 1-January 26 period. Winter 2020-21 is unique in that it is the only winter from those cases that had no mean trough anywhere over the CONUS. Snowfall totals today included: Allentown: Trace Bridgeport: 0.8" Islip: 0.1" New York City: 0.1" Newark: 0.5" The weak storm responsible for today's precipitation wil slowly move away overnight into tomorrow with a few additional periods of light preciptitation. All precipitation will end tomorrow followed by slow clearing. The coldest air mass so far this season will begin moving into the region on Thursday. In its wake, Friday and Saturday could see high temperatures only in the lower and middle 20s in much of the region. Central Park will likely see its first teens of the season. The ensembles suggest that the PNA could approach positive levels or even briefly go positive near the end of the month into the start of February. That could allow for the potential of a snow event during the February 1-2 period before milder air returns during the first week of February. The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.1°C for the week centered around January 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.85°C and the ENSO Region 3.4 anomaly has averaged -1.07°C. La Niña conditions will likely prevail at least through meteorological winter. The SOI was +25.16 today. Today, the preliminary Arctic Oscillation (AO) figure was -3.444. On January 25 the MJO was in Phase 6 at an amplitude of 1.890 (RMM). The January 24-adjusted amplitude was 1.903. Following a significant stratospheric warming event, the stratosphere is now cooling. The cooling will likely accelerate during the second half of January. As is typical for vortex-splitting events, the major piece of the polar vortex migrated to Eurasia. The end result has been an absence of severe cold in much of North America. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.0°.

Some of the ensemble members still suggest that the PNA could be nearing positive levels or even briefly reach positive levels by February 1. At the same time, the AO is forecast to remain negative, as has been the case throughout almost all of meteorological winter so far. This trend in the PNA would suggest a pattern with greater potential for significant snowstorms unlike at present. The February 1-2 event showing up on the guidance and highlighted by the ensembles for several days will bear watching.