donsutherland1

000 NOUS41 KBOX 041054 PNSBOX CTZ002>004-MAZ002>024-026-RIZ001>008-042254- Public Information Statement Spotter Reports National Weather Service Boston/Norton MA 554 AM EST Mon Jan 04 2021 The following are unofficial observations taken during the past 23 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/boston ********************STORM TOTAL SNOWFALL******************** LOCATION STORM TOTAL TIME/DATE COMMENTS SNOWFALL OF /INCHES/ MEASUREMENT CONNECTICUT ...Hartford County... Burlington 3.5 519 AM 1/04 Trained Spotter Bradley AP 1.7 1200 AM 1/04 CWOP ...Windham County... East Killingly 1.2 509 AM 1/04 NONE MASSACHUSETTS ...Essex County... Saugus 1.0 952 PM 1/03 Trained Spotter ...Hampden County... Longmeadow 2.0 1138 PM 1/03 Trained Spotter Westfield 1.3 933 PM 1/03 CWO West Springfield 1.0 821 PM 1/03 Ham Radio Agawam 1.0 1037 PM 1/03 Ham Radio ...Hampshire County... Easthampton 1.3 1035 PM 1/03 Ham Radio ...Middlesex County... Hopkinton 1.5 446 AM 1/04 Trained Spotter Lexington 1.3 1155 PM 1/03 Public ...Norfolk County... Medway 1.9 919 PM 1/03 Ham Radio Millis 1.2 1030 PM 1/03 Trained Spotter ...Worcester County... Grafton 1.8 1200 AM 1/04 Trained Spotter Westborough 1.7 949 PM 1/03 NWS Employee Milford 1.6 932 PM 1/03 Trained Spotter Leominster 1.5 1200 AM 1/04 Public Boylston 1.3 1041 PM 1/03 Trained Spotter Worcester 1.1 1144 PM 1/03 CWO Holden 1.0 841 PM 1/03 Ham Radio &&

000 NOUS41 KBGM 041149 PNSBGM NYZ009-015>018-022>025-036-037-044>046-055>057-062-PAZ038>040-043-044-047- 048-072-042349- Public Information Statement National Weather Service Binghamton NY 649 AM EST Mon Jan 4 2021 ...SNOWFALL REPORTS... Location Amount Time/Date Lat/Lon ...New York... ...Broome County... 2 E Vestal 6.0 in 1212 AM 01/04 42.08N/76.01W 2 SW Vestal Center 5.8 in 1015 PM 01/03 42.01N/76.05W 2 N Johnson City 5.7 in 0646 AM 01/04 42.15N/75.96W 1 S Nineveh 5.5 in 1220 AM 01/04 42.19N/75.60W Port Crane 5.1 in 0830 PM 01/03 42.17N/75.84W 4 SE Nineveh 5.0 in 1105 PM 01/03 42.17N/75.54W 3 SSW Sanitaria Spgs 4.2 in 0830 PM 01/03 42.13N/75.79W 2 E Whitney Point 4.0 in 0754 PM 01/03 42.33N/75.93W Vestal 4.0 in 0717 PM 01/03 42.08N/76.05W Nws Binghamton 3.8 in 1219 AM 01/04 42.21N/75.99W 1 SW Endwell 2.7 in 1015 PM 01/03 42.11N/76.03W Whitney Point 2.5 in 0511 PM 01/03 42.33N/75.97W Port Dickinson 2.2 in 0845 PM 01/03 42.14N/75.89W Endwell 2.0 in 0621 PM 01/03 42.12N/76.02W ...Chemung County... Van Etten 2.3 in 0432 PM 01/03 42.20N/76.55W Elmira 1.5 in 0736 PM 01/03 42.09N/76.81W ...Chenango County... 3 SW Greene 4.8 in 1010 PM 01/03 42.30N/75.81W Nineveh 4.0 in 0637 PM 01/03 42.20N/75.60W ...Delaware County... Hobart 4.0 in 0755 PM 01/03 42.37N/74.67W Delhi 2.5 in 0600 PM 01/03 42.28N/74.91W East Meredith 2.0 in 0234 PM 01/03 42.42N/74.88W ...Oneida County... 1 NNW Utica 0.5 in 0632 PM 01/03 43.11N/75.24W ...Onondaga County... 2 SSE North Syracuse 1.5 in 1100 PM 01/03 43.11N/76.11W Syracuse 1.0 in 0500 PM 01/03 43.04N/76.14W Marcellus 0.8 in 0700 PM 01/03 42.98N/76.34W ...Otsego County... Hartwick 6.0 in 1200 AM 01/04 42.65N/75.05W Milford 4.5 in 0900 PM 01/03 42.59N/74.95W 1 NNE Oneonta 4.0 in 0900 PM 01/03 42.47N/75.06W Unadilla 3.5 in 0950 PM 01/03 42.33N/75.32W 1 WSW Emmons 3.3 in 0900 PM 01/03 42.46N/75.04W 1 N Oaksville 3.1 in 0845 PM 01/03 42.75N/75.00W Edmeston 3.0 in 0930 PM 01/03 42.70N/75.24W ...Sullivan County... 1 ENE Callicoon Center 7.0 in 0620 AM 01/04 41.84N/74.95W Callicoon Center 6.0 in 1030 PM 01/03 41.83N/74.97W 1 ESE Callicoon Center 1.0 in 1045 AM 01/03 41.83N/74.95W ...Pennsylvania... ...Bradford County... New Albany 14.0 in 1100 PM 01/03 41.60N/76.44W 4 WSW South Branch 11.0 in 0945 PM 01/03 41.64N/76.50W 3 SSW West Burlington 7.1 in 1045 PM 01/03 41.72N/76.69W 3 ENE Alba 4.2 in 0845 PM 01/03 41.72N/76.77W Alba 4.0 in 1000 PM 01/03 41.71N/76.83W 1 SSE Towanda 4.0 in 0930 PM 01/03 41.76N/76.44W Litchfield 3.0 in 0730 PM 01/03 41.97N/76.43W ...Lackawanna County... Clarks Summit 6.2 in 0900 PM 01/03 41.49N/75.70W 1 SSE Clarks Summit 5.7 in 0800 PM 01/03 41.48N/75.70W Taylor 5.5 in 0845 PM 01/03 41.40N/75.72W 1 NW Throop 4.5 in 0800 PM 01/03 41.45N/75.61W 1 S Blakely 4.0 in 0800 PM 01/03 41.47N/75.60W Scranton 3.5 in 0718 PM 01/03 41.40N/75.67W 1 NE Moosic 3.2 in 1100 PM 01/03 41.37N/75.68W Richmondale 2.0 in 0511 PM 01/03 41.63N/75.50W ...Luzerne County... Edwardsville 5.0 in 0945 PM 01/03 41.26N/75.91W 2 WNW Harveys Lake 3.8 in 0900 PM 01/03 41.37N/76.06W 1 S Exeter 3.8 in 0800 PM 01/03 41.32N/75.82W Harveys Lake 2.5 in 0724 PM 01/03 41.36N/76.03W ...Susquehanna County... Dimock 4.0 in 0638 PM 01/03 41.75N/75.90W Harford 4.0 in 0559 PM 01/03 41.78N/75.70W Susquehanna 3.0 in 0744 PM 01/03 41.93N/75.60W Forest City 2.6 in 0600 PM 01/03 41.65N/75.47W ...Wayne County... Beach Lake 6.0 in 0541 AM 01/04 41.60N/75.15W 1 WNW Hawley 1.0 in 0954 AM 01/03 41.48N/75.19W 2 ESE Beach Lake 1.0 in 0950 AM 01/03 41.59N/75.11W ...Wyoming County... 1 NNW Factoryville 6.5 in 1015 PM 01/03 41.57N/75.79W &&

000 NOUS41 KPHI 041022 PNSPHI DEZ001>004-MDZ012-015-019-020-NJZ001-007>010-012>027-PAZ054-055-060>062-070- 071-101>106-042222- Public Information Statement National Weather Service Mount Holly NJ 522 AM EST Mon Jan 4 2021 ...SNOWFALL REPORTS... Location Amount Time/Date Provider ...New Jersey... ...Hunterdon County... Tewksbury Twp 0.5 in 0954 AM 01/03 Trained Spotter Lebanon 0.4 in 0953 AM 01/03 Trained Spotter ...Morris County... Ledgewood 1.5 in 1032 AM 01/03 Trained Spotter 1 NE Rockaway 1.5 in 1100 AM 01/03 Cocorahs Lake Hopatcong 1.5 in 1000 PM 01/03 Public 2 NNE Brookside 1.2 in 1030 AM 01/03 Trained Spotter Budd Lake 1.2 in 1140 AM 01/03 Public 2 ESE Randolph 0.9 in 1045 AM 01/03 Cocorahs Long Valley 0.8 in 0955 AM 01/03 Public Denville 0.6 in 1109 AM 01/03 Trained Spotter Montville 0.4 in 1205 PM 01/03 Trained Spotter ...Somerset County... Bridgewater 0.6 in 0925 PM 01/03 Trained Spotter Branchburg Twp 0.5 in 1005 AM 01/03 Public ...Sussex County... Wantage Twp 3.5 in 1041 PM 01/03 Public 4 SW Wantage 2.3 in 0245 AM 01/04 Trained Spotter ...Warren County... 1 NNW Stewartsville 1.6 in 0942 AM 01/03 Public 1 ENE Pohatcong Twp 1.6 in 1100 AM 01/03 Cocorahs Blairstown 1.1 in 1000 AM 01/03 Public 2 NW Hope 1.0 in 0926 AM 01/03 Trained Spotter ...Pennsylvania... ...Berks County... 2 W Colebrookdale Twp 1.4 in 0850 AM 01/03 Trained Spotter 1 N Huffs Church 1.1 in 1000 AM 01/03 Trained Spotter Douglassville 0.5 in 0830 AM 01/03 Trained Spotter ...Bucks County... Chalfont 0.5 in 0921 AM 01/03 Trained Spotter Furlong 0.5 in 0955 AM 01/03 Trained Spotter New Hope 0.4 in 0915 AM 01/03 Trained Spotter ...Carbon County... 2 ENE Palmerton 1.0 in 1100 AM 01/03 Trained Spotter ...Chester County... Elverson 1.0 in 0811 AM 01/03 Public East Nantmeal Twp 1.0 in 0838 AM 01/03 Trained Spotter East Coventry Twp 1.0 in 0900 AM 01/03 Trained Spotter 1 ENE Modena 0.5 in 0929 AM 01/03 Public 1 WNW Chesterbrook 0.5 in 0208 PM 01/03 Trained Spotter 2 SE Exton 0.4 in 0858 AM 01/03 Cocorahs ...Delaware County... 1 WNW Wayne 0.3 in 0916 AM 01/03 Trained Spotter ...Lehigh County... Macungie 2.0 in 0910 AM 01/03 Public Whitehall Twp 1.5 in 1138 AM 01/03 Public 1 W Hokendauqua 1.4 in 0935 AM 01/03 Public Center Valley 1.3 in 0930 AM 01/03 Trained Spotter 2 NE Emmaus 1.2 in 1100 AM 01/03 Trained Spotter 2 SSE Zionsville 1.0 in 0903 AM 01/03 Public 1 E Allentown 1.0 in 0922 AM 01/03 Public Coopersburg 1.0 in 1014 AM 01/03 Public Lehigh Valley International 1.0 in 0100 PM 01/03 ASOS North Whitehall Twp 0.8 in 0841 AM 01/03 Public ...Monroe County... Coolbaugh Twp 4.2 in 0930 PM 01/03 Trained Spotter Mount Pocono 4.0 in 0915 PM 01/03 Trained Spotter Bossardsville 3.5 in 1030 PM 01/03 Public ...Montgomery County... 1 SSE Trappe 1.0 in 0900 AM 01/03 Trained Spotter Gilbertsville 1.0 in 0916 AM 01/03 Trained Spotter New Hanover Twp 1.0 in 0918 AM 01/03 Public Pottstown 0.5 in 0850 AM 01/03 Public ...Northampton County... Eastlawn Gardens 1.5 in 1001 AM 01/03 Trained Spotter Bushkill Twp 1.5 in 1005 AM 01/03 Trained Spotter Bethlehem 1.4 in 1139 AM 01/03 Public Forks Twp 1.3 in 1020 AM 01/03 Trained Spotter Hellertown 1.1 in 0920 AM 01/03 Trained Spotter Palmer Heights 1.1 in 0957 AM 01/03 Public 1 NNW Danielsville 1.1 in 1020 AM 01/03 Trained Spotter Lower Mount Bethel Twp 1.0 in 0915 AM 01/03 Trained Spotter &&

Morning thoughts... Today will be partly sunny and milder than yesterday. Temperatures will likely reach the lower and middle 40s in much of the region. Likely high temperatures around the region include: New York City (Central Park): 42° Newark: 44° Philadelphia: 44° Mainly fair and somewhat milder than normal temperatures will prevail through much of the week.

Two photos from Armonk, NY from this evening: A short video clip:

A developing storm was bringing rain and snow to parts of the region this evening. Tomorrow will be drier, milder, with partly sunny skies. The likely continuation of Arctic blocking through at least the first 10 days of January would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait. Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, the EPO continues to show a possible transition that could lead to a trough's moving into the East. Arctic air will likely shift mainly to Eurasia. However, the evolving pattern could be sufficiently cold to afford opportunities for snowfall if the pattern evolves as currently shown on the EPS. The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.70°C and the ENSO Region 3.4 anomaly has averaged -1.15°C. La Niña conditions will likely prevail at least through the winter. The SOI was +23.42 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.437. On January 2 the MJO was in Phase 3 at an amplitude of 0.691 (RMM). The January 1-adjusted amplitude was 0.640. A significant stratospheric warming event is now in its early stages. The highest levels of the stratosphere will continue to warm through the first half of the first week of January. The mean zonal winds will likely reverse at 1 mb, 10 mb, and 30 mb making this a major warming event. Toward the end of the first week in January, the top layers of the stratosphere will likely begin to cool. 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. For now, blocking appears likely to continue through at least the first half of January.

Sleet has resumed falling.

At around 11 am, there was a burst of large snowflakes and sleet in and around Larchmont, NY. The precipitation quickly transitioned to all sleet and a mixture of sleet and rain. Before then, it produced some scattered coatings on colder surfaces. The large flakes of snow melted almost on contact with the pavement.

Morning thoughts... At 8 am, precipitation was advancing north and eastward through eastern Pennsylvania and central New Jersey. Rain was falling at such locations as Atlantic City and Philadelphia. Snow was falling just south of Allentown. Rain and sleet will move into Newark and New York City this morning and continue into the evening. Well north and west of those cities, there will be accumulating snow with 2”-4” and some locally higher amounts likely. Temperatures will likely reach the upper 30s and perhaps lower 40s in much of the region. Likely high temperatures around the region include: New York City (Central Park): 39° Newark: 40° Philadelphia: 42° Drier weather will return tomorrow.

Colder weather will return tonight into tomorrow. Tomorrow will see increasing clouds. A cold rain will overspread the Philadelphia, Newark, and New York City. Some sleet or wet snow is possible at the onset. North and west of the cities, there could be some accumulations. Poughkeepsie and Hartford could see 2"-4" snow. Boston could pick up 1"-2". Afterward, a generally mild regime will likely prevail. The likely continuation of Arctic blocking through at least the first 10 days of January would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait. Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, the EPO continues to show a possible transition that could lead to a trough's moving into the East. Arctic air will likely shift mainly to Eurasia. However, the evolving pattern could be sufficiently cold to afford opportunities for snowfall if the pattern evolves as currently shown on the EPS. The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.70°C and the ENSO Region 3.4 anomaly has averaged -1.15°C. La Niña conditions will likely prevail at least through the winter. The SOI was +18.05 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.910. On January 1 the MJO was in Phase 3 at an amplitude of 0.640 (RMM). The December 31-adjusted amplitude was 0.568. A significant stratospheric warming event is now in its early stages. The highest levels of the stratosphere will continue to warm through the first half of the first week of January. The mean zonal winds will likely reverse at 1 mb, 10 mb, and 30 mb making this a major warming event. Toward the end of the first week in January, the top layers of the stratosphere will likely begin to cool. 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. For now, blocking appears likely to continue through at least the first half of January.

I added the NAO, along with ISP.

HPN should get some accumulation. Probably not 4”, though. 80% of EPS members show 1” or more.

The AO/PNA data for the most recent storm (December 16-17) will be added once the final numbers are available in a few days.

Morning thoughts... Today will be partly sunny and mild. Temperatures will likely reach the lower 50s in much of the region. Likely high temperatures around the region include: New York City (Central Park): 53° Newark: 53° Philadelphia: 54° Clouds will increase tomorrow as another storm approaches the region. Some accumulating snow is a possibility to the north and west of New York City and Newark. From Philadelphia to New York City, mainly or all rain is likely. Boston could see some accumulation of snow.

@LibertyBell, I have created a quick table for the 6" or greater snowstorms for the NYC area locations. JFK had no snow data until 1959. The table can be found at: https://public.tableau.com/profile/don.sutherland#!/vizhome/NYCArea6Snowstorms/Dashboard1

An area of sleet changing to rain moved into the big cities of the northern Middle Atlantic region this afternoon. Overnight, periods of rain are likely and the temperature will likely hold steady and then begin to rise. Tomorrow will become partly sunny and much milder. Readings will likely rise into the 50s in much of the region. The likely continuation of Arctic blocking through at least the first 10 days of January would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait. Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, the EPO continues to show a possible transition that could lead to a trough's moving into the East. The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.70°C and the ENSO Region 3.4 anomaly has averaged -1.15°C. La Niña conditions will likely prevail at least through the winter. The SOI was +15.27 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.950. On December 31 the MJO was in Phase 3 at an amplitude of 0.566 (RMM). The December 30-adjusted amplitude was 0.460. A significant stratospheric warming event is now in its early stages. The highest levels of the stratosphere will continue to warm through the first half of the first week of January. The mean zonal winds will likely reverse at 1 mb, 10 mb, and 30 mb making this a major warming event. Toward the end of the first week in January, the top layers of the stratosphere could begin to cool. 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. For now, blocking appears likely to continue through at least the first half of January. In large account due to a very warm start to the month, January will likely feature above to much above normal temperatures across the northern Middle Atlantic and southern New England regions.

Sleet has commenced falling in Larchmont, NY.

I will have to work on that. It will require some time.

Morning thoughts... Clouds will increase this morning. The line of precipitation currently stretching from central Virginia northwestward into Indiana will reach the region this afternoon or evening. Some mixed or frozen precipitation is possible far north and west of New York City. Elsewhere, periods of rain are likely. Temperatures will likely reach the lower 40s across much of the region. Afterward, temperatures could hold steady or slowly rise overnight. Likely high temperatures include: New York City (Central Park): 43° Newark: 44° Philadelphia: 44° The first 10 days of January will likely feature much above normal temperatures. Afterward, a somewhat colder and potentially snowier pattern could evolve. 30-Day Verification: New York City (Central Park): Average daily forecast: 43.4° Average temperature: 43.8° Average error: 1.3° Newark: Average daily forecast: 44.6° Average temperature: 44.5° Average error: 1.2° Philadelphia: Average daily forecast: 45.1° Average temperature: 45.2° Average error: 1.3°

December is ending with a monthly mean temperature of 39.2° (1.7° above normal). The warmer than normal December was consistent with historic experience following an exceptionally warm November. Nevertheless, parts of the region are currently above normal in terms of seasonal snowfall. Seasonal snowfall amounts to date include: Albany: 27.4" (10.6" above normal) Baltimore: 1.6" (1.8" below normal) Binghamton: 51.6" (27.0" above normal) Boston: 17.3" (10.0" above normal) Bridgeport: 10.0" (4.2" above normal) Buffalo: 33.8" (2.4" below normal) Burlington: 10.9" (12.4" below normal) Caribou: 34.4" (0.7" below normal) Harrisburg: 11.7" (6.0" above normal) Islip: 7.5" (1.6" above normal) New York City: 10.5" (5.4" above normal) Newark: 11.9" (6.1" above normal) Philadelphia: 6.6" (2.9" above normal) Portland: 20.1" (5.0" above normal) Providence: 10.0" (0.2" below normal) Washington, DC: Trace (2.8" below normal) The preliminary AO average for December was -1.673. The AO was negative on 87% of days, at or below -1.000 on 77% of days, and at or below -2.000 on 35% of days. The likely continuation of Arctic blocking through at least the first 10 days of January would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait. Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, there is some indication on the EPS that a transition that could lead to a trough's moving into the East could get underway. The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.70°C and the ENSO Region 3.4 anomaly has averaged -1.15°C. La Niña conditions will likely prevail at least through the winter. The SOI was +32.12 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.984. On December 30 the MJO was in Phase 3 at an amplitude of 0.457 (RMM). The December 29-adjusted amplitude was 0.356. A significant stratospheric warming event is now in its early stages. The highest levels of the stratosphere will continue to warm through the first half of the first week of January. The mean zonal winds will likely reverse at 1 mb, 10 mb, and 30 mb making this a major warming event. Toward the end of the first week in January, the top layers of the stratosphere could begin to cool. 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. For now, blocking appears likely to continue through at least the first half of January. In large account due to a very warm start to the month, January will likely feature above to much above normal temperatures across the northern Middle Atlantic and southern New England regions.

In coming days, a positive to strongly positive EPO will coincide with a negative to strongly negative AO. Since 1950, there were 13 cases where the EPO was +1.000 or above while the AO was -1.500 or below for at least three consecutive days during the January 1-20 period. In 3 cases, the Arctic block extended southward into the Middle Atlantic region (January 1-4, 1955; January 15-17, 1998; and, January 1-3, 2003). The composite pattern is one that favors above to much above normal temperatures and little or no snowfall through at least the first 10 days of January in much or all of the Middle Atlantic Region and southern New England. Central and Upstate New York, along with central and northern New England would have greater opportunities for snowfall. Based on the latest guidance, there is a growing possibility that New York City’s Central Park could have a mean temperature of 40° or above during the January 1-10 period. There have been 20 prior cases since record-keeping began in 1869. It still appears possible that the January 10-15 period could mark a transition to a potentially snowier pattern. The key will be the continuation of Arctic blocking. Following such warm starts to January, 60% of the above cases saw less than 2” snow during the second half of January. However, in the 30% of cases with 4” or more snow during the second half of January, the AO was predominantly negative. Half of those cases saw 10” or more snow during the second half of January (1907, 1966, and 2005). Although a continuation of Arctic blocking cannot ensure a snowy second half of January—1998 is one such exception, largely on account of the super El Niño—the general absence of such blocking has seen little or no snowfall during the January 16-31 period following such warm starts to January. Things to watch for going forward if a snowy second half of January is likely: Continuation or reinforcement of the persistent AO- regime Development of a trough underneath the block that extends into the Middle Atlantic region The coldest air in the hemisphere will likely be focused on Europe on account of what increasingly looks like a polar vortex-splitting major stratospheric warming event. Severe cold’s migration to Europe does not mean that snowfall will be lacking. In the meantime, inspired by the work of Hooralph, here’s a sortable table of New York City’s 10” or greater snowstorms (1950-present): https://public.tableau.com/profile/don.sutherland#!/vizhome/NYC10Snowstorms1950-Present/Dashboard1

The new normals are implemented simultaneously worldwide. The WMO is scheduled to meet on the new normals on May 25, 2021. The new normals should then be adopted and implemented, probably starting in June. January-May anomalies might then be retroactively adjusted to fit the 1991-2020 base period.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 4.1 4.4 4.6 5.0 2.5 1.8 1.8 0.7 3.5

Morning thoughts... Rain will end from west to east from late this morning to mid-afternoon. Temperatures will likely hold nearly steady in the middle 40s across most of the region. Likely high temperatures around the region include: New York City (Central Park): 45° Newark: 46° Philadelphia: 46° Clouds will increase tomorrow and rain could arrive.

Tomorrow will be mostly cloudy and milder. Some rain showers or a period of rain is likely, especially during the morning hours. Well north and west of Newark and New York City, there could be some mixed or frozen precipitation. The likely continuation of Arctic blocking through at least the first 10 days of January would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait. Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, there is some indication on the EPS that a transition that could lead to a trough's moving into the East could get underway. The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.70°C and the ENSO Region 3.4 anomaly has averaged -1.15°C. La Niña conditions will likely prevail at least through the winter. The SOI was +25.01 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.446. On December 29 the MJO was in Phase 4 at an amplitude of 0.355 (RMM). The December 28-adjusted amplitude was 0.163. A significant stratospheric warming event is now in its early stages. The highest levels of the stratosphere will continue to warm through the first half of the first week of January. The mean zonal winds will likely reverse at 1 mb, 10 mb, and 30 mb making this a major warming event. Toward the end of the first week in January, the top layers of the stratosphere could begin to cool. 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. For now, blocking appears likely to continue through the first half of January. 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 December. December will likely finish with a mean temperature near 39.2°.