donsutherland1

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°.

Two final photos from the snowstorm following the sun’s coming out:

It just started snowing lightly in Larchmont.

It’s partly sunny in Larchmont. The North Shore of the Island has a better chance of receiving ocean effect snow than Larchmont.

5th earliest. November 26-27, 1898 had 10.0”.

The sun is now breaking out in Larchmont, NY.

The latest PNS doesn’t contain the near final numbers.

One short video clip from this morning:

Three photos from this morning:

For context, BGM’s 2-day record snowfall had been 35.3” (March 14-15, 2017). Prior to that, the record was 24.0” (February 19-20, 1972).

057 NOUS41 KBGM 171153 PNSBGM NYZ009-015>018-022>025-036-037-044>046-055>057-062-PAZ038>040-043-044-047- 048-072-172353- Public Information Statement National Weather Service Binghamton NY 653 AM EST Thu Dec 17 2020 ...SNOWFALL REPORTS... Location Amount Time/Date Provider ...New York... ...Broome County... 2 SW Nws Binghamton 41.0 in 0640 AM 12/17 NWS Employee Endicott 40.5 in 0550 AM 12/17 Trained Spotter Nws Binghamton 39.1 in 0605 AM 12/17 Official NWS Obs Johnson City 37.5 in 0455 AM 12/17 Public Vestal 37.0 in 0600 AM 12/17 Public 1 WSW Endwell 35.0 in 0510 AM 12/17 Public 2 E Vestal 31.7 in 0300 AM 12/17 NWS Employee 2 NNE Johnson City 31.0 in 0500 AM 12/17 Public Nanticoke 29.0 in 0636 AM 12/17 Public 2 SW Vestal Center 29.0 in 0235 AM 12/17 NWS Employee 2 NNW Port Crane 28.6 in 0615 AM 12/17 NWS Employee 1 WSW West Corners 28.5 in 0245 AM 12/17 NWS Employee 2 SE Union Center 27.0 in 0225 AM 12/17 NWS Employee Kirkwood 24.0 in 0625 AM 12/17 Public Whitney Point 21.0 in 0157 AM 12/17 Public ...Cayuga County... Union Springs 4.0 in 0530 AM 12/17 Public ...Chemung County... 1 ESE Horseheads North 13.0 in 0200 AM 12/17 Broadcast Media ...Chenango County... Preston 29.1 in 0535 AM 12/17 Cocorahs 1 N Mt Upton 25.0 in 0455 AM 12/17 Public Sherburne 21.0 in 0456 AM 12/17 Public Plymouth 19.5 in 0400 AM 12/17 Public Greene 15.0 in 0200 AM 12/17 Public ...Cortland County... 2 N Harford 15.0 in 0515 AM 12/17 Public 2 NW Mcgraw 11.5 in 0641 AM 12/17 Public ...Delaware County... Davenport 9.5 in 0110 AM 12/17 Public ...Oneida County... New Hartford 9.1 in 0601 AM 12/17 Trained Spotter Utica 8.6 in 0445 AM 12/17 Trained Spotter ...Onondaga County... Jamesville 8.0 in 0615 AM 12/17 Trained Spotter 1 NW Syracuse 3.5 in 0345 AM 12/17 Broadcast Media Baldwinsville 2.6 in 0626 AM 12/17 Trained Spotter ...Otsego County... Edmeston 24.0 in 0550 AM 12/17 Public 3 NE Mt Vision 20.5 in 0500 AM 12/17 Public Unadilla 19.5 in 0630 AM 12/17 Public Unadilla Forks 17.0 in 0600 AM 12/17 Public Laurens 12.0 in 0100 AM 12/17 Public ...Steuben County... Caton 18.0 in 0625 AM 12/17 Public ...Sullivan County... Kiamesha 12.0 in 0200 AM 12/17 Public ...Tioga County... 1 N Foster 38.0 in 0630 AM 12/17 NWS Employee Apalachin 38.0 in 0510 AM 12/17 Public Tioga Terrace 36.0 in 0445 AM 12/17 NWS Employee Newark Valley 35.0 in 0515 AM 12/17 Public Owego 26.0 in 0317 AM 12/17 Public ...Tompkins County... Freeville 16.0 in 0640 AM 12/17 Public Ithaca 9.0 in 0455 AM 12/17 Public 1 ESE Ithaca 9.0 in 0345 AM 12/17 Trained Spotter Etna 9.0 in 0315 AM 12/17 Trained Spotter ...Yates County... Italy Hill 8.5 in 0500 AM 12/17 Public Penn Yan 6.0 in 0445 AM 12/17 Public ...Pennsylvania... ...Bradford County... Litchfield 40.0 in 0445 AM 12/17 Trained Spotter 3 ENE Alba 36.0 in 0445 AM 12/17 Public 1 N Sayre 32.0 in 0500 AM 12/17 Public 1 SSW Sayre 32.0 in 0332 AM 12/17 Public 1 S Sayre 31.0 in 0545 AM 12/17 Public Alba 26.0 in 0420 AM 12/17 Trained Spotter Towanda 25.5 in 0234 AM 12/17 Public 3 WSW Browntown 20.0 in 0456 AM 12/17 Public ...Lackawanna County... 1 NNE Oakhill 8.0 in 0115 AM 12/17 Public Scranton 7.5 in 0100 AM 12/17 Amateur Radio ...Luzerne County... Dallas 12.5 in 0100 AM 12/17 Amateur Radio Lehman 12.0 in 1255 AM 12/17 Amateur Radio 1 SE Albert 10.0 in 0619 AM 12/17 Public ...Susquehanna County... Lenoxville 21.5 in 0217 AM 12/17 Public 1 N Montrose 18.0 in 0400 AM 12/17 Public Forest City 14.0 in 0630 AM 12/17 Public ...Wayne County... Hawley 14.0 in 0620 AM 12/17 Public &&

I agree. As long as the AO stays negative, there could be some more chances. As for Central Park, I suspect the final figure will be close to 10”. We’ll probably know soon.

IEMBot BGM @iembot_bgm · 13m At 5:50 AM EST, Endicott [Broome Co, NY] TRAINED SPOTTER reports HEAVY SNOW of 40.50 INCH https://mesonet.agron.iastate.edu/lsr/#BGM/202012171050/202012171050 IEMBot ALY @iembot_aly · 2m At 6:27 AM EST, Clifton Park [Saratoga Co, NY] SOCIAL MEDIA reports HEAVY SNOW of 26.50 INCH. ESTIMATED BY PICTURE https://mesonet.agron.iastate.edu/lsr/#ALY/202012171127/202012171127

Here is the daily listing. Climatological Data for New York-Central Park Area, NY (ThreadEx) - December 1896 Click column heading to sort ascending, click again to sort descending. Date Max Temperature Min Temperature Avg Temperature Avg Temperature Departure HDD CDD Precipitation Snowfall Sum 1241 892 - - 941 0 1.13 13.0 Average 40.0 28.8 34.4 -3.1 - - - - Normal 43.0 32.0 37.5 - 852 0 4.00 4.8 1896-12-01 32 26 29.0 -13.4 36 0 0.00 0.0 1896-12-02 26 22 24.0 -18.1 41 0 0.00 0.0 1896-12-03 32 21 26.5 -15.2 38 0 0.00 0.0 1896-12-04 43 26 34.5 -6.8 30 0 0.00 0.0 1896-12-05 46 35 40.5 -0.5 24 0 0.00 0.0 1896-12-06 51 42 46.5 5.9 18 0 0.00 0.0 1896-12-07 55 41 48.0 7.7 17 0 0.00 0.0 1896-12-08 54 38 46.0 6.1 19 0 0.00 0.0 1896-12-09 54 44 49.0 9.5 16 0 0.26 0.0 1896-12-10 50 44 47.0 7.8 18 0 0.00 0.0 1896-12-11 46 39 42.5 3.6 22 0 0.03 0.0 1896-12-12 50 37 43.5 5.0 21 0 0.00 0.0 1896-12-13 57 45 51.0 12.8 14 0 0.00 0.0 1896-12-14 47 35 41.0 3.1 24 0 0.00 0.0 1896-12-15 35 28 31.5 -6.0 33 0 0.02 S 1896-12-16 31 23 27.0 -10.2 38 0 0.55 7.0A 1896-12-17 35 23 29.0 -7.9 36 0 0.00 0.0 1896-12-18 44 30 37.0 0.4 28 0 0.00 0.0 1896-12-19 37 25 31.0 -5.3 34 0 0.00 0.0 1896-12-20 34 26 30.0 -6.0 35 0 0.00 0.0 1896-12-21 35 25 30.0 -5.8 35 0 0.00 0.0 1896-12-22 38 25 31.5 -4.0 33 0 0.12 S 1896-12-23 35 14 24.5 -10.7 40 0 0.15 6.0A 1896-12-24 22 9 15.5 -19.5 49 0 0.00 0.0 1896-12-25 32 15 23.5 -11.3 41 0 0.00 0.0 1896-12-26 34 23 28.5 -6.0 36 0 0.00 0.0 1896-12-27 29 14 21.5 -12.8 43 0 0.00 0.0 1896-12-28 31 20 25.5 -8.6 39 0 0.00 0.0 1896-12-29 37 25 31.0 -2.9 34 0 0.00 0.0 1896-12-30 43 38 40.5 6.8 24 0 0.00 0.0 1896-12-31 46 34 40.0 6.4 25 0 0.00 0.0 Reliable observation times are not available prior to 1982.

Morning thoughts... Snow will end early this morning as a strengthening storm moves away from the region. It will turn partly cloudy in much of the region during the afternoon, but remain windy. 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): 30° Newark: 32° Philadelphia: 34° In the wake of the snowstorm, temperatures will run below normal for the remainder of the week.

There was a 7.0” figure in 1896. It was a 2-day figure (12/15-16) in the daily data, but all but 0.02” precipitation fell on 12/16. That may explain why all 7.0” was allocated to 12/16.

Numerous mPING reports show either sleet or a snow-sleet mixture in Westchester County right now.

The precipitation has lightened. Sleet is now falling in Larchmont, NY.

Two photos from this evening:

A major snowstorm is now blanketing much of the region. By the time the snow ends tomorrow, much of central Pennsylvania to New England will have picked up a foot or more of snow. Estimated total snowfall amounts include: Allentown: 12"-18" Boston: 8"-16" Bridgeport: 8"-16" Hartford: 12"-18" Islip: 5"-10" New York City: 7"-14" Newark: 7"-14" Philadelphia: 4"-8" Poughkeepsie: 12"-18" Providence: 6"-12" Some areas could see 20" or above snowfall amounts. Since 2010, the three biggest December snowstorms for Boston, New York City, and Philadelphia were: Boston: 18.2", December 25-27, 2010 7.1", December 1-3, 2019 6.4", December 17, 2013 New York City: 20.0", December 25-27, 2010 5.0", December 14-15, 2013 4.6", December 9-10, 2017 Philadelphia: 12.4", December 25-27, 2010 8.6", December 8, 2013 4.1", December 9-10, 2017 During the December 10-31, 1950-2019 period, an AO- was the most important teleconnection for a significant Middle Atlantic (6" or more) snowstorm. Since 1950, the following percentage of 6" or greater snowstorms occurred when the AO was negative: Boston: 50%; New York City: 75%; and, Philadelphia: 88%. There were 8 snowstorms that brought 6" or more snow to at least two of the following cities: Boston, New York City, and Philadelphia. 7/8 (88%) occurred when the AO was negative. All storms from the subset from these 8 storms where 10" or more snow fell in at least one of those cities occurred with a negative AO. The most common synoptic pattern when at least two of the aforementioned cities picked up 6" or more snow (63%) was an AO-/PNA+ combination. The most recent such storm was the December 25-27, 2010 "Boxing Day Blizzard." With the persistence of Arctic blocking, uncertainty about the closing days of December has increased. At present, the guidance has backed off somewhat from the warmth that had been shown previously. 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 +28.65. Today, the preliminary Arctic Oscillation (AO) figure was -3.009. That is the lowest AO value since February 1, 2019 when the AO was -3.315. On December 15 the MJO was in Phase 5 at an amplitude of 0.868 (RMM). The December 14-adjusted amplitude was 1.070. 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. Based on sensitivity analysis applied to the latest guidance, there is an implied 56% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 38.4°.

It’s colder than modeled.