donsutherland1

Be safe. Have a great Christmas.

Morning thoughts... Today will be partly to mostly sunny. It will remain 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: 45° Philadelphia: 45° A strong storm will impact the region tomorrow into Friday. A general 1.00”-2.00” rainfall with locally higher amounts, along with high winds and unseasonably mild readings is likely. Colder air will return later Friday.

Sample size for the AO-/PNA+ during January 1-15, 1950-2020 is 346 days.

Under partly sunny skies, temperatures rose into the middle 40s across the region. High temperatures included: Bridgeport: 46°; Islip: 45°; New York City: 46°; Newark: 47°; and, Philadelphia: 47°. Across the Atlantic, it was even warmer. Record warmth prevailed in parts of western Europe. Daily record high temperatures included: Brussels: 57°; Chateauroux, France: 63°; Dresden: 59°; Grafenwoehr, Germany: 68° (new December record); Luxembourg: 54°; Paris-Le Bourget: 61°; and, Troyes, France: 61°. 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 Sunday. 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 and perhaps Saturday. 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% Further, an AO-/PNA+ pattern is especially favorable for moderate or significant snowstorms during the first half of January. For the January 1-15, 1950-2020 period, daily snowfall reached or exceeded 4" on 1.7% of days in New York City and 1.2% of days in Philadelphia. During AO-/PNA+ patterns, those respective frequencies were 2.3% and 1.7%. In short, moderate or significant snowfalls were 37% more common in New York City and 42% more common in Philadelphia during AO-/PNA+ patterns. The January 1-10 period likely has more potential than the days leading up to January. 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 +22.26 today. Today, the preliminary Arctic Oscillation (AO) figure was -1.718. The AO has now been negative for 20 consecutive days. On December 21 the MJO was in Phase 6 at an amplitude of 1.107 (RMM). The December 20-adjusted amplitude was 1.162. Based on the latest guidance, the probability of a significant stratospheric warming event near or just after the start of January has increased. The highest levels of the stratosphere will warm during the closing days of December. 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 69% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 38.2°.

I agree. I believe it will be classified as a moderate event when all is said and done.

Yes, there are differences of opinion. My belief is that the La Niña is more likely to fade than collapse. The most recent ENSO anomalies and the trade wind forecast suggest that this line of thinking of a slower decay has merit. Ultimately, we'll see how things turn out.

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.