donsutherland1

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

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

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

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

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

Two photos from this morning.

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

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

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

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

A quick video clip:

Flurries in Larchmont, NY.

Morning thoughts... At 8:05 am, pockets of snow, sleet, and freezing rain were moving north and eastward in central and southern Pennsylvania. That precipitation/will move into the region later this morning or early this afternoon. Today will be cloudy with periods of light snow, sleet, freezing rain, and rain developing. Minor accumulations are possible in New York City and Philadelphia (generally 1” or less). North and west of New York City, from the Hudson Valley into southern New England, 1”-3” snow is possible. East of a line running from Philadelphia to New York City, including Long Island, generally 0.5” or less of snow is likely. Temperatures will likely top out in the middle and upper 30s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 37° Newark: 38° Philadelphia: 39° Precipitation will end tomorrow morning.

Tomorrow into Wednesday morning, a weak system will come eastward bringing snow, sleet, freezing rain and rain to parts of the region. Snowfall amounts will be fairly light. Initial snowfall estimates include: Allentown: 2" or less Boston: 1"-3" Hartford: 1"-3" Islip: 0.5" or less New York City: 2" or less Newark: 1" or less Philadelphia: 1" or less Worcester: 2"-4" A few days later during January 28-29, another storm will impact parts of the East Coast. That storm will likely exit off the Southeast coast bringing some accumulating snow to parts of the Southeast and lower Middle Atlantic region, including the Richmond and Washington, DC areas. It now appears that the storm could develop too far offshore to produce an appreciable snowfall. AO-/PNA- patterns typically do not produce significant or major snowstorms for the Middle Atlantic or southern New England regions in late January or early February. During the January 20-February 7, 1950-2020 period, there have been 5 storms that brought 4" or more snow to at least two of the following cities--Boston, New York City, or Philadelphia--during an AO-/PNA- pattern. None of those storms brought 6" or more snow to two or more of those cities. Therefore, until the potential events are within 72 hours or less and the guidance suggests otherwise, the base case is against a widespread significant or major snowfall. Overall, the final week of January will feature generally below normal readings. The coldest air mass so far this season could bring the temperature below 20° in Central Park on one or two days late this week. The ensembles suggest that the PNA could briefly go positive near the end of the month and start of February. That could allow for the potential of a snow event during the February 1-2 period before milder air returns during the first week of February. Some of the guidance suggests that a period of much warmer than normal temperatures could develop for a time once the warmer air moves in. The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.1°C for the week centered around January 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.85°C and the ENSO Region 3.4 anomaly has averaged -1.07°C. La Niña conditions will likely prevail at least through meteorological winter. The SOI was +10.13 today. Today, the preliminary Arctic Oscillation (AO) figure was -3.380. On January 24 the MJO was in Phase 6 at an amplitude of 1.900 (RMM). The January 23-adjusted amplitude was 1.766. Following a significant stratospheric warming event, the stratosphere is now cooling. The cooling will likely accelerate during the second half of January. As is typical for vortex-splitting events, the major piece of the polar vortex migrated to Eurasia. The end result has been an absence of severe cold in much of North America. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Based on sensitivity analysis applied to the latest guidance, there is an implied 99% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.0°.

Probably midweek if the guidance remains as is.

The idea of a possible snow event during the February 1-2 period has some merit. First, there is a clustering of ensemble members around that timeframe. Second, that timeframe will coincide with a rise in the PNA to briefly positive levels allowing for a temporarily more favorable pattern. Having said that, it's too soon to lock in such an event, even as the probability is higher than climatology. It's also too soon to speculate as to potential impacts.

Morning thoughts... Today will be partly sunny and somewhat warmer than yesterday. Clouds will increase as the day progresses. Temperatures will likely top out in the middle and upper 30s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 36° Newark: 37° Philadelphia: 39° Tomorrow and tomorrow night, a weakening system will bring a light snowfall to parts of the region. An area running from Philadelphia to New York City remains in line for 1”-3” snow. Lesser amounts are likely to the east. A second larger storm will pass too far to the south and east to do more than graze much of the region. It increasingly appears that this storm will intensify too far off shore to bring a significant snowfall to the Middle Atlantic region.

Tomorrow will be dry and continued cold. On Tuesday into Tuesday night, a weakening system will come eastward bringing a swath of 1"-3" snowfall in an area running from Philadelphia to New York City and north and west of those areas. Areas just to the east of New York City could see little accumulation. A few days later during January 28-29, another storm will impact parts of the East Coast. That storm will likely exit off the Southeast coast bringing accumulating snow to parts of the Southeast and lower Middle Atlantic region. The heaviest snows could be focused on the Richmond to Washington, DC areas and eastward. That area could pick up light or moderate snowfall. As the storm rapidly intensifies offshore, it could still bring a period of heavy wind-swept snow to parts of eastern Virginia, Maryland's Eastern Shore, and extreme southeastern New Jersey. AO-/PNA- patterns typically do not produce significant or major snowstorms for the Middle Atlantic or southern New England regions in late January or early February. During the January 20-February 7, 1950-2020 period, there have been 5 storms that brought 4" or more snow to at least two of the following cities--Boston, New York City, or Philadelphia--during an AO-/PNA- pattern. None of those storms brought 6" or more snow to two or more of those cities. Therefore, until the potential events are within 72 hours or less and the guidance suggests otherwise, the base case is against a widespread significant or major snowfall. Overall, the final week of January will feature generally below normal readings. Milder temperatures will likely return during the first week of February. Some of the guidance suggests that a period of much warmer than normal temperatures could develop for a time. The ENSO Region 1+2 anomaly was -0.3°C and the Region 3.4 anomaly was -1.2°C for the week centered around January 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.73°C and the ENSO Region 3.4 anomaly has averaged -1.08°C. La Niña conditions will likely prevail at least through meteorological winter. The SOI was +5.66 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.462. On January 23 the MJO was in Phase 6 at an amplitude of 1.765 (RMM). The January 22-adjusted amplitude was 1.489. Following a significant stratospheric warming event, the stratosphere is now cooling. The cooling will likely accelerate during the second half of January. As is typical for vortex-splitting events, the major piece of the polar vortex migrated to Eurasia. The end result has been an absence of severe cold in much of North America. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Based on sensitivity analysis applied to the latest guidance, there is an implied 99% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.3°.

Morning thoughts... Today will be partly sunny and cold. Temperatures will likely top out in the lower 30s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 32° Newark: 34° Philadelphia: 34° On Tuesday and Tuesday night, a weakening system will bring a light snowfall to parts of the region. An area running from Philadelphia to New York City appear to be in line for 1”-3” snow. Lesser amounts are likely to the east. Later this week, a second larger storm will pass too far to the south and east to do more than graze much of the region. That storm’s heaviest snow will likely occur in eastern Virginia, Maryland’s Eastern Shore, and extreme southeastern New Jersey.

Tomorrow will be another fair and cold day. Afterward, parts of the East could see one or two snowfall possibilities during the upcoming week. During January 25-27, a system coming eastward could bring a swath of 1"-3" snows from Philadelphia to New York City with a few locally higher amounts. The higher amounts would likely be confined to the west of both cities. Areas just to the east of New York City could see little accumulation. A few days later during January 28-29, another storm will impact parts of the East Coast. That storm will likely exit off the Southeast coast bringing accumulating snow to parts of the Southeast and lower Middle Atlantic region. The heaviest snows could be focused on the Richmond to Washington, DC areas and eastward. That area could pick up a moderate snowfall. As the storm rapidly intensifies offshore, it could bring a period of heavy wind-swept snow to parts of eastern Virginia, Maryland's Eastern Shore, and extreme southeastern New Jersey. AO-/PNA- patterns typically do not produce significant or major snowstorms for the Middle Atlantic or southern New England regions in late January or early February. During the January 20-February 7, 1950-2020 period, there have been 5 storms that brought 4" or more snow to at least two of the following cities--Boston, New York City, or Philadelphia--during an AO-/PNA- pattern. None of those storms brought 6" or more snow to two or more of those cities. Therefore, until the potential events are within 72 hours or less and the guidance suggests otherwise, the base case is against a widespread significant or major snowfall. Overall, the final week of January will feature generally below normal readings. Milder temperatures will likely return during the first week of February. Some of the guidance suggests that a period of much warmer than normal temperatures could develop. The ENSO Region 1+2 anomaly was -0.3°C and the Region 3.4 anomaly was -1.2°C for the week centered around January 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.73°C and the ENSO Region 3.4 anomaly has averaged -1.08°C. La Niña conditions will likely prevail at least through meteorological winter. The SOI was +4.86 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.075. On January 22 the MJO was in Phase 6 at an amplitude of 1.489 (RMM). The January 21-adjusted amplitude was 1.073. Following a significant stratospheric warming event, the stratosphere is now cooling. The cooling will likely accelerate during the second half of January. As is typical for vortex-splitting events, the major piece of the polar vortex migrated to Eurasia. The end result has been an absence of severe cold in much of North America. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Based on sensitivity analysis applied to the latest guidance, there is an implied 99% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.5°.

The position and strength of the block.

It’s definitely having an impact. At the regional scale, not all of its impacts are evident.

The exceptionally warm SSTs may have played a role in influencing the position of the block.

Morning thoughts... Today will be partly sunny and cold. Temperatures will likely top out in the lower 30s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 33° Newark: 34° Philadelphia: 35° Tomorrow will be fair and continued cold.

Colder air drilled into the region with a few snow flurries and snow showers. A much colder air mass will cover the region during the weekend. Parts of the region could struggle to reach freezing tomorrow and again on Sunday. The closing week of January will likely be colder than normal across the region. Milder weather will likely return during the first week of February. Some of the guidance suggests that temperatures could surge to much above normal levels for a time. Meanwhile in northern Canada, Nunavut experienced another day with near record and record high temperatures. High temperatures included: Coral Harbour: 22° (old record: 20°, 1963) Iqaluit: 33° Kimmirut: 36° (old record: 14°, 2003) Kinngait: 29° (old record: 17°, 1980) Kugaaruk: 19° (old record: 6°, 1995) Naujaat: 25° (old record: 3°, 1995) Pangnirtung: 32° (old record: 20°, 2000) Qikiqtarjuaq: 15° (missed record from 2013 by 0.2°C) The abnormal warmth will likely continue in Nunavut through tomorrow. As Arctic blocking persists, next week could feature two opportunities for snowfall. The earlier event (January 25-27 timeframe) will likely focus its heaviest snows on the Philadelphia to New York City area. The latter event (January 28-29 timeframe) will likely focus its heaviest snows in an area running from Richmond to Washington, DC. A widespread significant snowfall (6" or above) still appears relatively unlikely, especially for the first event. A light or moderate snowfall (2"-4" or 3"-6") remains more likely. However, some of the guidance suggests that the second storm could rapidly intensify, so there is a greater degree of uncertainty for that event in terms of amounts. AO-/PNA- patterns typically do not produce significant or major snowstorms for the Middle Atlantic or southern New England regions in late January or early February. During the January 20-February 7, 1950-2020 period, there have been 5 storms that brought 4" or more snow to at least two of the following cities--Boston, New York City, or Philadelphia--during an AO-/PNA- pattern. None of those storms brought 6" or more snow to two or more of those cities. Therefore, until the potential events are within 72 hours or less and the guidance suggests otherwise, the base case is against a widespread significant or major snowfall. The ENSO Region 1+2 anomaly was -0.3°C and the Region 3.4 anomaly was -1.2°C for the week centered around January 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.73°C and the ENSO Region 3.4 anomaly has averaged -1.08°C. La Niña conditions will likely prevail at least through meteorological winter. The SOI was +1.14 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.238. On January 21 the MJO was in Phase 6 at an amplitude of 1.071 (RMM). The January 20-adjusted amplitude was 0.684. Following a significant stratospheric warming event, the stratosphere is now cooling. The cooling will likely accelerate during the second half of January. As is typical for vortex-splitting events, the major piece of the polar vortex migrated to Eurasia. The end result has been an absence of severe cold in much of North America. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Based on sensitivity analysis applied to the latest guidance, there is an implied 95% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.2°.