donsutherland1

I continue to believe that proclamations that the La Niña is near its demise are premature. The trade winds have been strong for some time now (the SOI was even +30 or above for three consecutive days for the first time since January 2012), and are forecast to strengthen further. One already saw a fairly sharp cooling in Region 1+2 over the past week. Through February, I believe a gradual fade is more likely than a collapse. Overall, the DJF tri-monthly period will likely have an ENSO anomaly consistent with La Niña.

Morning thoughts... Today will become partly to mostly sunny. It will be mild. Temperatures will likely top out in the lower and middle 40s across most of the region. Likely high temperatures around the region include: New York City (Central Park): 44° Newark: 46° Philadelphia: 45° A strong storm will impact the region Thursday into Friday. Moderate to heavy rain, high winds, and unseasonably mild readings ahead of the frontal passage early Friday can be expected later Thursday and Thursday night.

Following the December 16-17 snowstorm, the temperature anomaly in New York City's Central Park swung to negative values (0.1° below normal). Following the push of dry air into the region, temperatures rose into the middle 40s. As a result, the monthly departure has moved back to slightly above normal levels. Overnight, parts of the region could see some rain and snow showers. Overcast skies will yield to partly sunny conditions tomorrow. A strong storm could pass to the west of the region on Thursday bringing a period of moderate to heavy rain, high winds, and unseasonably warm temperatures before colder air returns afterward. In the wake of that storm, the unseasonably warm air will be driven into Atlantic Canada where record high temperatures are likely Friday and perhaps Saturday. Unseasonably cold air will push into Florida. Record low temperatures are possible in some parts of the state, especially along the Gulf Coast and southern portions of the Florida Peninsula, on Friday. The likely continuation of Arctic blocking into at least the first week of January will provide a higher than climatological probability for above normal snowfall for the December 21-January 10 period. The AO- is particularly important for moderate or significant snowfalls in the New York City and Philadelphia areas. For the December 15-January 15, 1950-2020 period, the following percentages of select snowstorms have occurred when the AO was negative: New York City: 4" or more: 66% 6" or more: 80% 10" or more: 86% Philadelphia: 4" or more: 81% 6" or more: 85% 10" or more: 100% The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 16. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.57°C and the ENSO Region 3.4 anomaly has averaged -1.17°C. La Niña conditions will likely prevail at least through the winter. The SOI was +21.12 today. Today, the preliminary Arctic Oscillation (AO) figure was -1.141. On December 20 the MJO was in Phase 6 at an amplitude of 1.162 (RMM). The December 19-adjusted amplitude was 1.031. Based on the latest guidance, no significant stratospheric warming event is into the final days of December. The highest levels of the stratosphere will warm. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall. The large snowfall that just took place provides a strong contrary signal to the below normal snowfall idea. Should blocking continue, the probability of above normal snowfall would likely increase. The recent 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. For now, blocking appears likely to continue into the start of January. Based on sensitivity analysis applied to the latest guidance, there is an implied 60% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 38.0°.

Some drier air has worked in, so there may be several hours of partly to mostly sunny skies in parts of the region. That should leader to temperatures running several degrees above modeled highs.

Unfortunately, it will likely be mostly cloudy to completely overcast.

There was a dusting on colder surfaces in Rye, NY. South of there in Mamaroneck and Larchmont, there was no accumulation.

Morning thoughts... Today will be variably cloudy. Temperatures will likely top out in the upper 30s and lower 40s across most of the region. Likely high temperatures around the region include: New York City (Central Park): 41° Newark: 41° Philadelphia: 43° After some overnight rain or snow showers, tomorrow will become partly cloudy.

I used zoom. It was about 3 feet away.

Tomorrow will be partly to mostly cloudy. A period of light snow or flurries is possible tomorrow night into Tuesday morning. A strong storm could pass to the west of the region after midweek bringing a period of moderate to heavy rain, high winds, and unseasonably warm temperatures before colder air returns afterward. The likely continuation of Arctic blocking will provide a higher than climatological probability for above normal snowfall for the December 21-January 10 period. The AO- is particularly important for moderate or significant snowfalls in the New York City and Philadelphia areas. For the December 15-January 15, 1950-2020 period, the following percentages of select snowstorms have occurred when the AO was negative: New York City: 4" or more: 66% 6" or more: 80% 10" or more: 86% Philadelphia: 4" or more: 81% 6" or more: 85% 10" or more: 100% The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 9. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.62°C and the ENSO Region 3.4 anomaly has averaged -1.43°C. La Niña conditions will likely prevail at least through the winter. The SOI was +10.02 today. Today, the preliminary Arctic Oscillation (AO) figure was -1.001. On December 19 the MJO was in Phase 5 at an amplitude of 1.031 (RMM). The December 18-adjusted amplitude was 0.864. Based on the latest guidance, no significant stratospheric warming event is likely into the final week of December. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall. The large snowfall that just took place provides a strong contrary signal to the below normal snowfall idea. Should blocking continue, the probability of above normal snowfall would likely increase. The recent 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. For now, blocking appears likely to continue into the start of January. Based on sensitivity analysis applied to the latest guidance, there is an implied 55% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 37.9°.

Following a light snowfall that dusted colder surfaces, a period of drizzle and then mist followed. Some photos from late this afternoon:

Some light snow:

Morning thoughts... At 8:35, an area of light snow extended from northwestern Maryland to near Montreal. There was some additional light snow in southeastern Pennsylvania and rain south of there. Some flurries were scattered across other parts of New Jersey, including one area between Lakewood and Howell. Today will be variably cloudy. Some rain and snow showers are likely. A few places could pick up a coating of snow. Temperatures will be somewhat warmer than yesterday. Temperatures will likely top out in the middle and upper 30s across most of the region. Likely high temperatures around the region include: New York City (Central Park): 37° Newark: 38° Philadelphia: 39° Tomorrow will be a little milder than today.

To date, New York City's Central Park has had a monthly temperature anomaly of 0.1° below normal. However, the month will swing back to positive departures in coming days as slow moderation continues. Tomorrow will be variably cloudy with some rain and snow showers possible. A strong storm could pass to the west of the region after midweek bringing a period of moderate to heavy rain, high winds, and unseasonably warm temperatures before colder air returns afterward. Parts of western Canada again experienced record cold. At Norman Wells, Northwest Territories, where the temperature plunged to a record -54° yesterday, the temperature fell to -52° today. That broke the daily record of -50°, which was set in 1956. With the persistence of Arctic blocking, uncertainty about the closing days of December has increased. A possible piece of an Arctic air mass could even push into parts of the region on or just after December 25. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 9. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.62°C and the ENSO Region 3.4 anomaly has averaged -1.43°C. La Niña conditions will likely prevail at least through the winter. The SOI was +30.57 today. That is the 3rd consecutive day on which the SOI was +30.00 or above. The last time that happened was January 24-26, 2012. Today, the preliminary Arctic Oscillation (AO) figure was -1.506. On December 18 the MJO was in Phase 5 at an amplitude of 0.869 (RMM). The December 17-adjusted amplitude was 0.785. Based on the latest guidance, no significant stratospheric warming event is into the final week of December. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall. The large snowfall that just took place provides a strong contrary signal to the below normal snowfall idea. Should blocking continue, the probability of above normal snowfall would likely increase. The recent 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. For now, blocking appears likely to continue into the start of January. Based on sensitivity analysis applied to the latest guidance, there is an implied 53% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 37.9°.

There is model consensus for weakening. But it’s premature to assume that it dissipates entirely in the near-term. On Monday, we’ll get the latest weekly numbers to see where things stood for the week centered around December 16.

Those La Niña events developed prior to June-July-August. In any case, the widespread warm SSTAs over the Pacific, the IOD, and AO- have laid the basis for a different outcome this winter. Things are now leaning decidedly toward a snowier outcome in the northern Middle Atlantic region into New England. Unless the AO blocking is sustained, it’s too soon to be confident about snowfall totals from Baltimore and southward.

The December 16-17, 2020 snowstorm dumped 10.5" snow on New York City. December cases when 10" or more snow falls have generally seen 20" or more additional snowfall from January to the last snowfall. The historic data suggests that seasonal guidance notwithstanding, the New York City area now has a high probability of seeing 30" or more seasonal snowfall. January-May Snowfall (1869-2020) following December Monthly Snowfall of 10" or More: Number of cases by DJF ENSO: La Niña: 8 Neutral: 13 El Niño: 6 Total: 27 What could result in less snowfall: 1. Collapse of the ongoing La Niña and/or 2. The persistent AO- blocking yields to a sustained AO+ regime

Morning thoughts... Today will be mostly sunny in much of the region. It will remain unseasonably cold. Temperatures will likely top out in the lower and 30s across most of the region. Likely high temperatures around the region include: New York City (Central Park): 31° Newark: 33° Philadelphia: 33° Tomorrow will be variably cloudy with some rain and snow showers, along with moderating temperatures.

IMO, the NWS is an invaluable resource. It is among the most effective and beneficial federal entities and provides proof to skeptics that government can perform at a consistently high level. I appreciate and applaud all that NWS does even with severe resource constraints in recent years.

That’s fairly common, unfortunately.

@bluewave was discussing the areas where 20”-40” snow just fell as having the highest risk of a flood threat, not here.

To date, the Arctic Oscillation (AO) has averaged -1.678 this month. It has been negative on 89% of days. It has been -1.000 or below 78% of the time and -2.000 or below on 39% of the days. A negative AO has been present in more than three-quarters of cases where Philadelphia and New York City saw 6" or greater snowstorms during the December 10-31 period, one of which occurred during December 16-17. Since 2000, December snowfall exceeded 6" or more in 5/7 (71%) of cases in both New York City and Philadelphia when the AO averaged -1.000 or below in December. In Philadelphia, seasonal snowfall exceeded 20" or more in 80% of those December cases when 6" or more snow fell and 30" or more in 60% of those cases. In New York City, seasonal snowfall exceeded 30" or more in all those December cases with 6" or more snowfall and 40" or more in 80% of those cases. The recent snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. Nevertheless, there remains a chance that the current La Niña could adversely influence the pattern leading to a disappearance of the blocking. Were blocking to disappear, snowfall prospects would diminish. For now, blocking appears likely to continue into the start of January. Temperatures will slowly moderate this weekend. Tomorrow will be fair and still cool. Sunday will be variably cloudy with some rain and snow showers possible. A strong storm could pass to the west of the region after midweek. With the persistence of Arctic blocking, uncertainty about the closing days of December has increased. A possible piece of an Arctic air mass could even push into parts of the region on or just after December 25. Frigid Arctic air is currently centered in northwestern Canada. Earlier today, near record and record cold was reported in parts of the Northwest Territories. At Norman Wells, the temperature fell to -53° (old record: -50°, 1961). At Yellowknife, the temperature fell to a near-record -48°. Historic experience following exceptionally warm November cases suggests that a warmer than normal December remains the base case. Almost 90% of cases with a November mean temperature of 51.5° or above in Central Park (2020 saw the temperature average a record 52.9° in November) went on to record a warmer than normal December and just over three-quarters of such cases saw December register a monthly mean temperature of 40.0° or above. Sustained Arctic blocking will produce a much cooler outcome. The monthly temperature anomaly could wind up only somewhat above normal. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 9. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.62°C and the ENSO Region 3.4 anomaly has averaged -1.43°C. La Niña conditions will likely prevail at least through the winter. The SOI was +34.10. Today, the preliminary Arctic Oscillation (AO) figure was -2.035. On December 17 the MJO was in Phase 5 at an amplitude of 0.790 (RMM). The December 16-adjusted amplitude was 0.845. Based on the latest guidance, no significant stratospheric warming event is into the final week of December. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall. The large snowfall that just took place provides a strong contrary signal to the below normal snowfall idea. Should blocking continue, the probability of above normal snowfall would likely increase. Based on sensitivity analysis applied to the latest guidance, there is an implied 54% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 38.0°.

Great point about the flood potential.

The latest PNS: 000 NOUS41 KOKX 172217 PNSOKX CTZ005>012-NJZ002-004-006-103>108-NYZ067>075-078>081-176>179-180951- Public Information Statement National Weather Service New York NY 517 PM EST Thu Dec 17 2020 ...SNOWFALL REPORTS... Location Amount Time/Date Provider ...Connecticut... ...Fairfield County... 5 NNW Danbury 14.5 in 0915 AM 12/17 Trained Spotter Shelton 12.0 in 0930 AM 12/17 Amateur Radio Danbury 11.6 in 1210 PM 12/17 Trained Spotter 4 SSE Sherman 11.5 in 0515 AM 12/17 Trained Spotter 2 NW Wilton 10.5 in 0940 AM 12/17 Trained Spotter 3 ESE Georgetown 10.5 in 0715 AM 12/17 Trained Spotter 4 WNW Newtown 10.2 in 0700 AM 12/17 Cocorahs 1 NNE Bethel 10.0 in 0930 AM 12/17 Amateur Radio Ridgefield 10.0 in 0800 AM 12/17 Public 1 E Bethel 10.0 in 0630 AM 12/17 Cocorahs 2 WNW Monroe 9.5 in 0745 AM 12/17 Cocorahs Bridgeport 9.4 in 0100 PM 12/17 Official NWS Obs 3 N Bethel 9.3 in 0916 AM 12/17 Cocorahs Newtown 4.6 SSW 9.0 in 0900 AM 12/17 COCORAHS Darien 1.8 ENE 9.0 in 0740 AM 12/17 COCORAHS 4 N Ridgefield 9.0 in 0630 AM 12/17 Cocorahs 3 NE Fairfield 8.5 in 0700 AM 12/17 Cocorahs 2 ENE New Canaan 8.4 in 0800 AM 12/17 Cocorahs 1 SE Danbury 8.4 in 0700 AM 12/17 Cocorahs Easton 8.0 in 1230 PM 12/17 Public Fairfield 8.0 in 0930 AM 12/17 Amateur Radio 4 NE Georgetown 8.0 in 0815 AM 12/17 Cocorahs Wilton 7.5 in 0930 AM 12/17 Public 2 SSW Monroe 7.0 in 0600 AM 12/17 Cocorahs Norwalk 6.3 in 1130 AM 12/17 Public 1 SSE Trumbull 6.0 in 0630 AM 12/17 Cocorahs 2 ESE New Canaan 5.7 in 0700 AM 12/17 Cocorahs ...Middlesex County... Killingworth 12.0 in 0930 AM 12/17 Amateur Radio 1 N Higganum 11.0 in 0800 AM 12/17 Cocorahs Essex 10.2 in 0605 AM 12/17 Public Westbrook 9.0 in 0930 AM 12/17 Amateur Radio 2 ESE Killingworth 9.0 in 0700 AM 12/17 Cocorahs Clinton 6.0 in 0930 AM 12/17 Amateur Radio ...New Haven County... Wallingford 12.0 in 0930 AM 12/17 Amateur Radio Guilford 12.0 in 0930 AM 12/17 Amateur Radio 3 ESE Cheshire 11.5 in 0700 AM 12/17 Cocorahs Hamden 11.2 in 0100 PM 12/17 Public Cheshire 11.0 in 0400 PM 12/17 Amateur Radio 3 ENE Naugatuck 10.0 in 0800 AM 12/17 Cocorahs Waterbury 9.6 in 0830 AM 12/17 Trained Spotter North Haven 9.5 in 1235 PM 12/17 Trained Spotter 2 WNW Wallingford 9.5 in 0700 AM 12/17 Cocorahs 1 SSE North Madison 9.0 in 0700 AM 12/17 Cocorahs 1 E Seymour 9.0 in 0700 AM 12/17 Cocorahs Prospect 1.9 ENE 9.0 in 0600 AM 12/17 COCORAHS West Haven 8.5 in 0900 AM 12/17 Trained Spotter Branford 8.5 in 1030 AM 12/17 Trained Spotter 1 NW New Haven 8.5 in 0810 AM 12/17 Public Waterbury 1.3 WNW 8.5 in 0700 AM 12/17 COCORAHS 2 WSW Madison 8.5 in 0700 AM 12/17 Cocorahs Woodmont 8.0 in 0930 AM 12/17 Amateur Radio Milford 7.0 in 0930 AM 12/17 Amateur Radio Southbury 2.6 S 7.0 in 0700 AM 12/17 COCORAHS Naugatuck 1.7 NNE 6.5 in 0640 AM 12/17 COCORAHS East Haven 6.0 in 0930 AM 12/17 Amateur Radio ...New London County... 3 N Norwich 11.5 in 0830 AM 12/17 Public Lebanon 10.0 in 0100 PM 12/17 Public New London 9.5 in 0400 PM 12/17 Trained Spotter Gales Ferry 9.4 in 0920 AM 12/17 Trained Spotter Ledyard Center 9.3 in 0900 AM 12/17 Public 1 E Ledyard Center 9.1 in 0800 AM 12/17 Trained Spotter 2 SE Norwich 8.0 in 0700 AM 12/17 CO-OP Observer Central Waterford 2.7 SSW 8.0 in 0700 AM 12/17 COCORAHS 3 NW Niantic 8.0 in 0600 AM 12/17 Cocorahs 3 NNW Mystic 7.4 in 0700 AM 12/17 Cocorahs Mystic 1.6 W 6.5 in 0700 AM 12/17 COCORAHS Stonington 0.5 NNE 6.0 in 0800 AM 12/17 COCORAHS Mystic 0.9 W 6.0 in 0700 AM 12/17 COCORAHS Pawcatuck 1.8 SSE 5.7 in 0700 AM 12/17 COCORAHS ...New Jersey... ...Bergen County... Fort Lee 10.1 in 1100 AM 12/17 Public East Rutherford 9.5 in 1030 AM 12/17 Trained Spotter Westwood 9.3 in 1020 AM 12/17 Trained Spotter 1 SE Oakland 8.0 in 0800 AM 12/17 Cocorahs 2 NNW Ramsey 7.8 in 1100 AM 12/17 Public Ridgewood 7.3 in 1000 AM 12/17 Trained Spotter Bergenfield 7.1 in 0846 AM 12/17 Trained Spotter Dumont 7.0 in 1035 AM 12/17 Broadcast Media Fair Lawn 6.5 in 0852 AM 12/17 Public Franklin Lakes 6.3 in 0800 AM 12/17 Trained Spotter Glen Rock 6.1 in 1200 PM 12/17 Public Tenafly 1.3 W 5.8 in 0730 AM 12/17 COCORAHS 1 NNW Saddle Brook 5.4 in 1016 AM 12/17 Cocorahs ...Essex County... Newark Airport 11.4 in 0100 PM 12/17 Official NWS Obs 1 NNE West Orange 7.5 in 1040 AM 12/17 Public Cedar Grove 7.5 in 1015 AM 12/17 Public 1 ENE North Caldwell 7.1 in 0500 AM 12/17 Trained Spotter 1 N Montclair 7.0 in 0800 AM 12/17 Cocorahs 1 W Verona 6.7 in 0845 AM 12/17 Cocorahs Belleville 6.4 in 0945 AM 12/17 Trained Spotter 1 SE Maplewood 5.6 in 0800 AM 12/17 Cocorahs ...Hudson County... Kearny 10.5 in 1137 AM 12/17 Cocorahs 1 NE East Newark 10.2 in 1115 AM 12/17 CO-OP Observer Harrison 10.2 in 1115 AM 12/17 Trained Spotter ...Passaic County... 5 W Bloomingdale 8.5 in 0700 AM 12/17 Mesonet 1 WSW Haledon 8.0 in 0800 AM 12/17 Cocorahs 1 E Prospect Park 6.5 in 0700 AM 12/17 Cocorahs Little Falls Twp 0.5 WNW 5.8 in 0700 AM 12/17 COCORAHS ...Union County... Elizabeth 8.1 in 0926 AM 12/17 Trained Spotter Union 6.7 in 0938 AM 12/17 Public Cranford 6.4 in 0810 AM 12/17 Trained Spotter Plainfield 6.0 in 1000 AM 12/17 Trained Spotter Westfield 1.2 SE 5.6 in 0700 AM 12/17 COCORAHS New Providence 0.8 ESE 4.5 in 0800 AM 12/17 COCORAHS ...New York... ...Bronx County... 1 NE Fordham 12.8 in 1100 AM 12/17 Public 1 S East Tremont 12.4 in 0145 PM 12/17 Trained Spotter 1 NW Mott Haven 12.2 in 1245 PM 12/17 CO-OP Observer 1 NNE East Tremont 12.1 in 0200 PM 12/17 Public 1 W Woodlawn 10.5 in 0630 AM 12/17 Public 1 SE Washington Heights 9.0 in 0700 AM 12/17 Public Riverdale 6.7 in 0700 AM 12/17 Emergency Mngr ...Kings County... Bay Ridge 9.6 in 1130 AM 12/17 Emergency Mngr 1 W Greenpoint 9.0 in 1145 AM 12/17 Public 3 SSE Flatbush 7.5 in 1000 AM 12/17 Public 2 NE Coney Island 6.5 in 0830 AM 12/17 Trained Spotter 1 SSW Flatbush 5.9 in 0945 AM 12/17 Broadcast Media ...Nassau County... Syosset 8.0 in 1200 PM 12/17 Trained Spotter Melville 8.0 in 1200 PM 12/17 Trained Spotter 1 E Searingtown 7.6 in 0730 AM 12/17 Cocorahs West Hempstead 7.5 in 1145 AM 12/17 Public East Williston 7.3 in 1201 PM 12/17 Public 1 ENE Syosset 7.0 in 0825 AM 12/17 CO-OP Observer East Meadow 6.2 in 1215 PM 12/17 NWS Employee Farmingdale 5.9 in 1220 PM 12/17 NWS Employee 1 SSE Merrick 5.6 in 0100 PM 12/17 Trained Spotter 2 SSE Plainedge 5.5 in 1233 PM 12/17 Public Floral Park 5.5 in 0800 AM 12/17 Trained Spotter Plainview 5.3 in 1211 PM 12/17 Public 2 E Roosevelt 5.2 in 0600 AM 12/17 Trained Spotter ...New York County... Central Park 10.5 in 0100 PM 12/17 Central Park Conservancy 2 SSE Greenwich Village 9.9 in 1105 AM 12/17 Emergency Mngr 1 NNE Greenwich Village 7.1 in 0900 AM 12/17 Cocorahs ...Orange County... 1 S Walden 14.0 in 0700 AM 12/17 Cocorahs Newburgh 13.1 in 1000 AM 12/17 Trained Spotter Monroe 13.0 in 0900 AM 12/17 Trained Spotter 3 SW Greenwood Lake 12.0 in 0800 AM 12/17 Cocorahs Middletown 11.8 in 1015 AM 12/17 Fire Dept/Rescue 1 WNW Gardnertown 11.5 in 1045 AM 12/17 Trained Spotter New Windsor 11.2 in 0955 AM 12/17 Public 1 W Kiryas Joel 11.0 in 1100 AM 12/17 Trained Spotter Warwick 11.0 in 1050 AM 12/17 Trained Spotter Port Jervis 2.9 ESE 10.8 in 0630 AM 12/17 COCORAHS 3 WNW Warwick 10.0 in 0700 AM 12/17 Cocorahs ...Putnam County... Mahopac 13.0 in 1100 AM 12/17 Trained Spotter Brewster 11.7 in 0945 AM 12/17 Trained Spotter Putnam Valley 10.5 in 1015 AM 12/17 Broadcast Media Cold Spring 10.0 in 0930 AM 12/17 Amateur Radio 4 N Carmel 10.0 in 0800 AM 12/17 COOP Beacon 4.2 ESE 10.0 in 0700 AM 12/17 COCORAHS 1 N Cold Spring 9.5 in 0715 AM 12/17 Public ...Queens County... Jamaica 11.8 in 1140 AM 12/17 Emergency Mngr Whitestone 10.5 in 1130 AM 12/17 Public Laguardia Airport 10.1 in 0100 PM 12/17 Official NWS Obs 3 S Jackson Heights 9.3 in 0230 PM 12/17 Trained Spotter 2 NW Ozone Park 9.1 in 1055 AM 12/17 Public 2 SSW Russell Gardens 8.0 in 1210 PM 12/17 Trained Spotter 1 SW Russell Gardens 8.0 in 1000 AM 12/17 Trained Spotter 1 NNW Whitestone 8.0 in 0645 AM 12/17 Public 1 SSE Whitestone 7.5 in 1130 AM 12/17 Trained Spotter Howard Beach 7.5 in 0800 AM 12/17 Trained Spotter Kennedy Airport 7.2 in 0100 PM 12/17 Official NWS Obs ...Richmond County... 1 WNW Todt Hill 7.0 in 1007 AM 12/17 Public 1 W Huguenot 6.7 in 1100 AM 12/17 Broadcast Media 2 SW New Dorp 6.6 in 0700 AM 12/17 Cocorahs ...Rockland County... New City 10.0 in 1100 AM 12/17 Trained Spotter 1 NNW Pomona 10.0 in 0930 AM 12/17 Amateur Radio Chestnut Ridge 9.5 in 0945 AM 12/17 Public 1 NW New City 9.2 in 0915 AM 12/17 Trained Spotter 1 NW Stony Point 7.0 in 0700 AM 12/17 Trained Spotter Nyack 6.8 in 0909 AM 12/17 Public ...Suffolk County... Miller Place 8.2 in 0240 PM 12/17 Public Commack 8.1 in 0900 AM 12/17 Public East Northport 8.0 in 0852 AM 12/17 Trained Spotter 1 SSW Nesconset 8.0 in 0845 AM 12/17 Cocorahs Upton 7.7 in 0100 PM 12/17 Official NWS Obs Islip Airport 7.4 in 0100 PM 12/17 Official NWS Obs Port Jefferson Station 0.3 S 7.2 in 0900 AM 12/17 COCORAHS 2 E Yaphank 7.0 in 0214 PM 12/17 Fire Dept/Rescue Centerport 6.9 in 0650 AM 12/17 CO-OP Observer Smithtown 6.7 in 0200 PM 12/17 Public 1 ENE Calverton 6.5 in 0700 AM 12/17 CO-OP Observer 1 SSE Stony Brook 6.4 in 1030 AM 12/17 NWS Employee Orient Point 6.0 in 0800 AM 12/17 COOP Bay Shore 0.5 ESE 5.7 in 0900 AM 12/17 COCORAHS Riverhead 5.2 in 1000 AM 12/17 NWS Employee 1 NNW Remsenburg-Speonk 5.2 in 0930 AM 12/17 Public 1 SSE Manorville 4.9 in 0800 AM 12/17 Cocorahs Sayville 4.5 in 0900 AM 12/17 NWS Employee 1 SW West Islip 4.0 in 0755 AM 12/17 Cocorahs Amityville 0.6 NNE 3.5 in 0900 AM 12/17 COCORAHS Southampton 3.3 in 1008 AM 12/17 Trained Spotter 1 SSW Islip Terrace 3.3 in 0700 AM 12/17 Trained Spotter ...Westchester County... Mamaroneck 12.5 in 1214 PM 12/17 Public Mount Kisco 12.5 in 1055 AM 12/17 Public New Rochelle 12.2 in 1115 AM 12/17 Public White Plains 12.0 in 1200 PM 12/17 Public Rye 11.5 in 1110 AM 12/17 Public Armonk 11.1 in 1005 AM 12/17 Public 2 E Yorktown Heights 11.0 in 0800 AM 12/17 Cocorahs 2 S Peach Lake 10.9 in 0138 PM 12/17 Trained Spotter 5 S Peach Lake 10.7 in 0715 AM 12/17 Cocorahs 2 NW Yorktown Heights 10.5 in 0930 AM 12/17 Amateur Radio 2 SSW Golden`s Bridge 10.5 in 0930 AM 12/17 Amateur Radio Peekskill 10.5 in 0800 AM 12/17 Cocorahs Croton-on-Hudson 10.0 in 1145 AM 12/17 Trained Spotter Hastings-on-Hudson 9.0 in 0205 PM 12/17 Public 2 ESE Putnam Valley 9.0 in 0700 AM 12/17 CO-OP Observer Irvington 8.2 in 1230 PM 12/17 Trained Spotter 1 N Harrison 8.0 in 0800 AM 12/17 Cocorahs 2 ENE Elmsford 6.0 in 0800 AM 12/17 Trained Spotter &&

Morning thoughts... Today will become partly to mostly sunny in much of the region. It will remain unseasonably cold. Temperatures will likely top out in the lower and middle 30s across most of the region. Likely high temperatures around the region include: New York City (Central Park): 33° Newark: 34° Philadelphia: 36° Temperatures will moderate during the weekend.

In the wake of a snowstorm that brought widespread 10" or above amounts from New York City into New England with several areas of excessive amounts of 30" or more, tomorrow will be fair and unseasonably cold. With the persistence of Arctic blocking, uncertainty about the closing days of December has increased. A possible piece of an Arctic air mass could even push into parts of the region on or just after December 25. Historic experience following exceptionally warm November cases suggests that a warmer than normal December remains the base case. Almost 90% of cases with a November mean temperature of 51.5° or above in Central Park (2020 saw the temperature average a record 52.9° in November) went on to record a warmer than normal December and just over three-quarters of such cases saw December register a monthly mean temperature of 40.0° or above. The probability of December's having a 40.0° or above mean temperature has fallen sharply with the development of strong AO blocking. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 9. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.62°C and the ENSO Region 3.4 anomaly has averaged -1.43°C. La Niña conditions will likely prevail at least through the winter. The SOI was +34.10. That is the highest figure since March 17, 2018 when the SOI reached +35.90. Today, the preliminary Arctic Oscillation (AO) figure was -2.620. On December 16 the MJO was in Phase 5 at an amplitude of 0.839 (RMM). The December 15-adjusted amplitude was 0.880. Based on the latest guidance, no significant stratospheric warming event is into the final week of December. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall. The large snowfall that just took place provides a strong contrary signal to the below normal snowfall idea. Should blocking continue, the probability of above normal snowfall would likely increase. Based on sensitivity analysis applied to the latest guidance, there is an implied 55% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 38.1°.