donsutherland1

As of 3 pm PDT, the temperature had reached 79° at Seattle. That set a new March record high temperature. The previous monthly record was 78°, which was set on March 29, 2004. The ENSO Region 1+2 anomaly was +0.70°C and the Region 3.4 anomaly was +1.00°C for the week centered around March 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.45°C and the ENSO Region 3.4 anomaly has averaged +0.80°C. Similar ENSO conditions will likely persist through much of March. The SOI was -1.44 today. It has been negative for 41 out of the last 42 days. Today's preliminary value of the Arctic Oscillation (AO) was +1.940. The AO has now been positive for 40 consecutive days. The last time the AO was positive for at least that long was during the April 13, 2018 through June 3, 2018 period when the AO was positive for 52 consecutive days. Historic probabilities favor the continuation of a predominantly positive AO through the remainder of March. On March 18, the MJO was in Phase 3 at an amplitude of 0.382 (RMM). The amplitude was lower than the March 17-adjusted figure of 0.481. The MJO could approach or reach Phase 2 in the next day or so. Thursday into Friday, a strong storm will move along the coastline of the Northeastern United States. Much of the region could receive 0.50"-1.00" rain with locally higher amounts. Another system could bring the risk of precipitation to the region during the March 26-28 period. Some of the guidance suggests the possibility of at least some frozen precipitation from that latter system. Such an outcome would be consistent with historical experience. A small number of the 12z EPS members showed 4" or more snow. Since 1869, New York City has had 10 cases during the March 1-7 period when 6.0" or more snow fell and the average temperature was 32.0° or below. All 10 cases had additional measurable snowfall afterward.

Seattle reached 79 degrees at 3 pm PDT. That set a new monthly record high temperature.

I agree about the importance of the storm track. Last year, ISP saw 4.6" snow on April 2 and NYC saw 5.5" snow. It has been uncommon for ISP or NYC to have 2 or more consecutive years during which 2" or more snow fell during the March 25-April 30 period. ISP has had 1 such case (1996 and 1997) during its 57-year climate record; NYC has had 3. ISP would equate to around 3 over the same period of time as NYC's climate record. Neither location has had 2 or more consecutive years when 4" or more snow fell during the March 25-April 30 period. Then again, the 2010s have set a lot of snowfall records, so one can't completely rule out such a scenario, which appeared on a few of the EPS members (0z run).

Later this week, a storm will likely bring rain to parts of the Northeast, especially coastal areas. Accumulating snow is possible in higher elevations across Upstate New York, Quebec, and New England. The greatest risk of a moderate or significant snowfall (4” or more) exists in the higher elevations of Quebec north and west of Quebec City and in an area running across western Maine and northern New Hampshire. Next week could favor a better chance at a measurable snowfall. Some of the guidance is suggesting that the March 26-28 period could offer a window of opportunity for a measurable snowfall in at least parts of the Philadelphia to Boston corridor. But at this time scale, uncertainty remains high. The 0z EPS ensemble mean figures are: Boston: 3.0” (8/51 members at 4” or more; 4 of those members show 10” or more) New York City: 2.0” (5/51 members at 4” or more) Philadelphia: 1.0” (4/51 members at 4” or more) The 0z GGEM also highlighted the possibility of measurable snow. Some historical data is provided below for perspective as it relates to 4” or greater snowfalls for Boston, New York City, and Philadelphia in the March 25-April 30 timeframe: Even in Boston, a 4” or greater snowfall would be an infrequent event this late in the season.

A very weak system passed well south of the region today. However, none of its precipitation reached the New York City region and nearby suburbs. The ENSO Region 1+2 anomaly was +0.70°C and the Region 3.4 anomaly was +1.00°C for the week centered around March 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.45°C and the ENSO Region 3.4 anomaly has averaged +0.80°C. Similar ENSO conditions will likely persist through much of March. The SOI was -8.86 today. It has been negative for 40 out of the last 41 days. Today's preliminary value of the Arctic Oscillation (AO) was +0.900. The AO has now been positive for 39 consecutive days. The last time the AO was positive for at least that long was during the April 13, 2018 through June 3, 2018 period when the AO was positive for 52 consecutive days. Historic probabilities favor the continuation of a predominantly positive AO through the remainder of March. On March 17, the MJO was in Phase 3 at an amplitude of 0.480 (RMM). The amplitude was lower than the March 16-adjusted figure of 0.635. The MJO could approach or reach Phase 2 in the next day or so. By the midweek, the temperature could be warmer than normal. There is some chance of another brief push of cooler air late in the week as a strong system passes offshore, possibly grazing the region with some light precipitation on Thursday into Friday. Another system could bring the risk of precipitation to the region during the March 26-28 period. Some of the guidance suggests the possibility of at least some frozen precipitation from that latter system. Such an outcome would be consistent with historical experience. Since 1869, New York City has had 10 cases during the March 1-7 period when 6.0" or more snow fell and the average temperature was 32.0° or below. All 10 cases had additional measurable snowfall afterward. Since 1950, 9/11 (82%) of New York City's 4" or greater snowstorms that occurred on or after March 20 occurred when the PNA was negative. The two that occurred with a positive PNA were the only two cases that featured an ENSO Region 1+2 anomaly > 0°C. None of the 11 cases occurred with the PNA at +1.000 or above. Smaller snowfalls, some of which exceeded 3.0", did occur when the PNA was at or above +1.000.

On numerous occasions this winter, the ECMWF has shown the snowiest solution that was at odds with the other guidance in the medium term and then wound up incorrect. The PNA+ and lack of support from its ensemble members suggests that this could be another such case. Seasonal climatology also argues for caution when it comes to the ECMWF’s snowy solution.

The ENSO Region 1+2 anomaly was +0.50°C and the Region 3.4 anomaly was +1.00°C for the week centered around March 6. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.50°C and the ENSO Region 3.4 anomaly has averaged +0.69°C. Similar ENSO conditions will likely persist through much of March. The SOI was -9.10 today. It has been negative for 39 out of the last 40 days. Today's preliminary value of the Arctic Oscillation (AO) was +0.454. The AO has now been positive for 38 consecutive days. The last time the AO was positive for at least that long was during the April 13, 2018 through June 3, 2018 period when the AO was positive for 52 consecutive days. Historic probabilities favor the continuation of a predominantly positive AO through the remainder of March. On March 16, the MJO was in Phase 3 at an amplitude of 0.637 (RMM). The amplitude was lower than the March 15-adjusted figure of 0.706. The MJO could approach or reach Phase 2 in the next day or so. Tonight into tomorrow morning, a fast-moving weak system could bring some light rain or snow across parts of the northern Middle Atlantic region. However, the precipitation looks to pass south of New York City. By the middle of the week, temperatures could again be rising to levels above seasonal norms. There is some chance of another brief push of cooler air late in the week as a strong system passes offshore. Another system could bring the risk of precipitation to the region during the March 26-28 period.

Following last night's line of thunderstorms, some of which brought small hail to parts of the region, a cooler air mass has returned to the region. Temperatures struggled to reach 50° whereas yesterday the mercury soared into the 70s. The ENSO Region 1+2 anomaly was +0.50°C and the Region 3.4 anomaly was +1.00°C for the week centered around March 6. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.50°C and the ENSO Region 3.4 anomaly has averaged +0.69°C. Similar ENSO conditions will likely persist through much of March. The SOI was -9.53 today. It has been negative for 38 out of the last 39 days. Today's preliminary value of the Arctic Oscillation (AO) was +0.677. The AO has now been positive for 37 consecutive days. The last time the AO was positive for at least that long was during the April 13, 2018 through June 3, 2018 period when the AO was positive for 52 consecutive days. Historic probabilities favor the continuation of a predominantly positive AO through the remainder of March. On March 15, the MJO was in Phase 3 at an amplitude of 0.707 (RMM). The amplitude was lower than the March 14-adjusted figure of 0.805. The MJO will likely remain in Phase 3 at a low amplitude for at least several days. Tomorrow night into Monday morning, a fast-moving weak system could bring some light rain or snow across parts of the northern Middle Atlantic region. However, most of the precipitation looks to pass south of New York City. Cities most likely to pick up a small accumulation (probably a coating to an inch) include Harrisburg, Philadelphia, and Trenton. By the middle of the week, temperatures could again be rising to levels above seasonal norms. There is some chance of another brief push of cooler air late in the week. Overall, the implied probability of a colder than normal March has rebounded to 66% based on sensitivity analysis applied to the latest guidance. In short, even as there have been fluctuations in the implied probabilities on account of the recent warmth, the overall idea of a colder than normal March as a whole for the New York City remains on track. April looks to be warmer than normal as per multiple pieces of guidance. Finally, through March 16 at 5 pm, Atlanta has received 0.0" snow. Since snowfall recordkeeping began, Atlanta has never had a winter when it received less than a trace of snow. Atlanta's snowfall records go back to 1928-29.

I am sorry to read of your mom’s passing. You have my fullest condolences.

Courtesy of the combination of breaks of sunshine and an exceptionally warm air mass aloft, today saw the warmest readings since last autumn. In a few locations, the mercury approached or reached the daily record high temperature. Some highlights: Albany: 72° (tied record set in 1989) -- warmest reading since October 11, 2018 (72°) Allentown: 74° -- warmest reading since October 11, 2018 (79°) New York City: 75° -- warmest reading since October 11, 2018 (77°) Newark: 77° -- warmest reading since October 11, 2018 (81°) Philadelphia: 77° -- warmest reading since October 11, 2018 (83°) Poughkeepsie: 72° -- warmest reading since October 11, 2018 (75°) Teterboro: 76° -- warmest reading since November 2, 2018 (79°) Trenton: 74° (old record: 72°, 1971 and 2002) -- warmest reading since October 11, 2018 (82°) Wilmington, DE: 79° -- warmest reading since October 11, 2018 (83°) The ENSO Region 1+2 anomaly was +0.50°C and the Region 3.4 anomaly was +1.00°C for the week centered around March 6. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.50°C and the ENSO Region 3.4 anomaly has averaged +0.69°C. Similar ENSO conditions will likely persist through much of March. The SOI was -8.33 today. It has been negative for 37 out of the last 38 days. Today's preliminary value of the Arctic Oscillation (AO) was +1.381. The AO has now been positive for 36 consecutive days. The last time the AO was positive for at least that long was during the April 13, 2018 through June 3, 2018 period when the AO was positive for 52 consecutive days. Historic probabilities favor the continuation of a predominantly positive AO through the remainder of March. On March 14, the MJO moved into Phase 3 with at a low amplitude, 0.809 (RMM). The amplitude was lower than the March 13-adjusted figure of 1.063. The MJO will likely remain in Phase 3 at a low amplitude for at least several days. Following today's warmth, a brief shot of cooler air will move into the East. There is even the possibility of some light rain or snow across parts of the northern Middle Atlantic region on Monday morning. However, by late next week temperatures could again be rising to levels above seasonal norms. In part, the forecast strongly positive PNA will contribute to that outcome. Unlike during January and the first half of February, shorter wave lengths now result in the PNA's having a direct relationship with regional temperatures and an inverse relationship with snowfall prospects. During the March 16-31, 1950-2018 period, the mean temperature in New York City was +1.1° above climatology when the PNA was +1.000 or above. The mean temperature was 0.5° below climatology when the PNA was negative. In terms of snowfall, the frequency of measurable snow events in New York City was somewhat less than half of climatology when the PNA was +1.000 or above while that frequency was just over 40% above climatology when the PNA was negative. Based on the latest guidance, New York City's average temperature for the March 16-31 period could be approximately 1.6° above normal. As a result, the implied probability of a colder than normal March in New York City has decreased to 55%.

At 1 pm, the temperature was 71° in Philadelphia, 71° in Newark, and 70° in New York City. Those are the first 70° or warmer readings at those locations since November 2, 2018.

All other variables held constant, it would support milder readings—not exceptional warmth, but still on the warm side of normal for the closing week of March. Both the CFSv2 and EPS support such an idea.

The PNA+ could last for two weeks.

A brief spring preview is in order for tomorrow. Temperatures will very likely surge into the 60s as far north as southern New England and to or even above 70° in Washington, D.C. The ENSO Region 1+2 anomaly was +0.50°C and the Region 3.4 anomaly was +1.00°C for the week centered around March 6. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.50°C and the ENSO Region 3.4 anomaly has averaged +0.69°C. Similar ENSO conditions will likely persist through much of March. The SOI was -14.12 today. It has been negative for 36 out of the last 37 days. Today's preliminary value of the Arctic Oscillation (AO) was +1.990. The AO has now been positive for 35 consecutive days. The last time the AO was positive for at least that long was during the April 13, 2018 through June 3, 2018 period when the AO was positive for 52 consecutive days. Historic probabilities favor the continuation of a predominantly positive AO through the remainder of March. On March 13, the MJO was in Phase 4 at an amplitude of 1.059 (RMM). The amplitude was somewhat lower than the March 12-adjusted figure of 1.296. The MJO will likely move into Phase 3 and/or at a low amplitude in the next day or two. Following tomorrow's warmth, a brief shot of cooler air will move into the East. However, by late next week temperatures could again be rising above seasonal norms. In part, the forecast strongly positive PNA will contribute to that outcome. Unlike during January and the first half of February, shorter wave lengths now result in the PNA's having a direct relationship with regional temperatures and an inverse relationship with snowfall prospects. During the March 16-31, 1950-2018 period, the mean temperature in New York City was +1.1° above climatology when the PNA was +1.000 or above. The mean temperature was 0.5° below climatology when the PNA was negative. In terms of snowfall, the frequency of measurable snow events in New York City was somewhat less than half of climatology when the PNA was +1.000 or above while that frequency was just over 40% above climatology when the PNA was negative.

Yesterday's 14.0" daily snowfall total at Cheyenne broke the daily record of 9.3", which was set in 1973. It also tied for Cheyenne's 4th biggest daily snowfall on record. That city's biggest daily snowfalls are: 1. 19.8", November 20, 1979 2. 17.3", April 20, 1984 3. 15.9", May 18, 2003 4. 14.0", January 24, 1921; May 2, 1942; and, March 13, 2019 March-May has had the highest frequency of days with 10" or more snow. Those 3 months account for 70% of Cheyenne's days with 10" or more snow. Records go back to 1871.

The record-intense blizzard is now winding down in areas that were battered yesterday. So far, early data shows that the guidance suggesting 12"-18" snow in parts of the affected region has verified. Cheyenne picked up 14.0" snow yesterday. However, there is a large snowfall data void in the region as no snowfall reports were available in such locations as Limon, CO and Pierre, SD, among others (Chinook's posted message above concerning measurements likely explains the lack of such reports).

An extreme blizzard was bringing blinding snows and fierce winds to parts of Colorado, Nebraska, South Dakota and Wyoming this evening. Blizzard conditions will likely continue into tomorrow afternoon and possibly evening in the affected region. The ENSO Region 1+2 anomaly was +0.50°C and the Region 3.4 anomaly was +1.00°C for the week centered around March 6. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.50°C and the ENSO Region 3.4 anomaly has averaged +0.69°C. Similar ENSO conditions will likely persist through much of March. The SOI was -14.84 today. It has been negative for 35 out of the last 36 days. Today's preliminary value of the Arctic Oscillation (AO) was +2.527. The AO has now been positive for 34 consecutive days. The last time the AO was positive for at least that long was during the April 13, 2018 through June 3, 2018 period when the AO was positive for 52 consecutive days. Historic probabilities favor the continuation of a predominantly positive AO through the remainder of March. On March 12, the MJO was in Phase 4 at an amplitude of 1.299 (RMM). The amplitude was somewhat lower than the March 11-adjusted figure of 1.494. The MJO could lose amplitude in coming days as it heads back toward Phase 3. As the seasonal tendency has favored high amplitudes, there is a distinct possibility that it could reach Phase 3 at a high amplitude. Afterward, there is some possibility it could reach Phase 2 before resuming forward progression. However, based on historic experience, it is more likely than not that the MJO won't go all the way back to Phase 2. Temperatures will likely remain generally above normal through the next 3-6 days across much of the region. The warmth could peak on Friday with readings in the 60s extending as far north as southern New England and 70s into the greater Washington, DC area. Beyond that, the possibility exists for a return to cooler temperatures relative to normal into the closing week of the month. However, this period could be short-lived. At that point, there could be some possibility for another measurable snowfall in at least parts of the region. March 18 might offer the strongest prospect of such a snowfall.

From the NWS at Cheyenne: At 2:04 PM MDT, 5 E Hemingford [Box Butte Co, NE] MESONET reports NON-TSTM WND GST of M89 MPH. MESONET STATION NE023, 5 E HEMINGFORD NE - HEMINGFORD HWY 385 (HMG).

Transition from rain to blizzard at Denver (next hour should make the blizzard official):

Mesoscale Discussion 0194 NWS Storm Prediction Center Norman OK 1127 AM CDT Wed Mar 13 2019 Areas affected...Southeast Colorado...Northeast Colorado...the Nebraska panhandle...and far southwest South Dakota Concerning...Blizzard Valid 131627Z - 131930Z SUMMARY...Heavy snow is expected through the afternoon with snowfall rates of 1 to 2 inches per hour. In areas where it is currently raining, a transition to snow is expected within the next 2 hours. Blizzard conditions are expected across this entire region by early afternoon. DISCUSSION...A rapidly deepening surface low with a minimum pressure around 971 mb is currently located in southeast Colorado. This surface cyclone is likely near peak intensity as current water vapor analysis suggests the system has become mostly vertically stacked and occlusion will likely begin soon. This is supported by a relative stall in surface pressure falls in southeast Colorado between 15Z and 16Z after several hours of 2 to 3 mb per hour falls. Rapidly falling heights have quickly cooled the column and transitioned rain to snow across much of the Front Range with moderate to heavy snow. There are still a few locations which are still observing rain, but these locations should transition to snow in the next few hours. In addition, snowfall rates have rapidly increased over the last 2 hours as dCVA, frontogenesis, and isentropic ascent have maximized across this region. As mid-level temperatures continue to rapidly cool, thermal profiles will support occasional convective elements with thundersnow potential across much of this region. In addition to the increasing snowfall rates, sustained surface northerly winds of 25 to 30 mph with gusts 40 to 50 mph are present across most of this area. Current surface temperatures near freezing are likely limiting significant additional visibility reduction due to blowing snow, but this will change quickly in the next few hours as temperatures continue to fall. By early afternoon, most of this region will likely be observing blizzard conditions with visibilities less than a tenth of a mile in many locations. ..Bentley.. 03/13/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LBF...UNR...GLD...PUB...BOU...CYS... LAT...LON 39180521 39790581 40520606 41170618 42270614 42990581 43430522 43550407 43470328 43080173 42300169 41230221 40270282 39030329 38590359 38380429 38650500 39180521

It’s a truly amazing storm. The images from the radar are remarkable.

From WPC: NWS WPC‏Verified account @NWSWPC 2h2 hours ago New preliminary record low pressure set at Pueblo, CO! At 7am MDT Pueblo reported a sea level pressure of 975.5 MB. Their previous record low pressure was 976.6 MB, with records dating back to 1893. From NWS Pueblo: NWS Pueblo‏Verified account @NWSPueblo 1h1 hour ago NWS Pueblo Retweeted ColoClimateCenter Not official, but La Junta is at 973.4 mb central pressure! #COwx #Colorado

It looked like a double-phaser the last few runs I saw.

Even as the weather is poised to be fairly quiet in the East over the next several days with the thermometer reaching springlike readings in the 60s on Friday and possibly 70° or better in the Washington, DC area, the extreme storm moving across the Plains States will present a meteorological marvel. Its central pressure will probably bottom out close to 970 +/- a few mb late today. It will produce a severe blizzard in parts of the Plains, centered around southeast Wyoming, northwest Nebraska, and southwest South Dakota where 12"-18" of wind-whipped snow will fall creating whiteout conditions and huge drifts.

Also, New York City has never had consecutive years during which April saw a 4" or greater snowstorm since regular recordkeeping began in 1869.