donsutherland1

Some of the guidance has suggested the potential for a moderate to significant snowfall (4" or more snow) in and around Richmond next week. An AO-/PNA- pattern is a favorable pattern for snow events in Richmond. Since 1950, there have been 24 days on which 2" or more snow fell during the January 20-February 10, 1950-2020 period in Richmond. Based on the AO/PNA states, the breakdown was as follows: AO-/PNA-: 25% AO-/PNA+: 46% AO+/PNA-: 4% AO+/PNA+: 17% AO-: 71% AO+: 29% PNA-: 29% PNA+: 71% Below is a bubble chart showing the distribution of such days, with bubble size based on the amount of snowfall. The AO and PNA are forecast to be negative through the remainder of January. Richmond's largest snowstorms during the above January 20-February 10, 1950-2020 timeframe were: 6.4", February 7, 1979 (AO: -1.696; PNA: -1.080) 5.6", January 22-23, 1954 (AO: -0.082; PNA: -0.747) 5.3", February 2, 1972 (AO: -1.896; PNA: -1.097) In addition, a storm brought 3.0" on January 20, 2000 during an AO-/PNA- state. A much larger snowstorm occurred shortly thereafter. The three largest AO-/PNA- storms also brought accumulating snowfall to to Washington, DC: January 22-23, 1954: 6.4" February 2, 1972: 3.4" February 7, 1979: 5.6" Only one of those storms brought more than 1.0" snow as far north as New York City: the February 7, 1979 storm, which brought 5.0" to Central Park.

0.2” at both JFK and LGA.

I suspect that the second storm could be even more suppressed, if anything. If so, it is possible that it would bring little or nothing to the New York City or Newark areas.

Morning thoughts... At 7:45 am, a line of snow showers, with some embedded pockets of moderate to heavy snow, stretched from central Vermont down to western Massachusetts. That area of snow was pushing eastward. The potential existed for Boston to pick up a small accumulation later this morning or early this afternoon. That area of snow was associated with a strong push of colder air. The frontal passage will likely be dry in the New York City and Philadelphia areas. As a result, under partly sunny skies, readings will likely top out in the lower and middle 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 45° Newark: 47° Philadelphia: 47° Tomorrow will be fair and much colder. The temperature will struggle just to reach freezing in parts of the region.

Temperatures again rose into the lower 40s across much of the region today. The remainder of the week will be fair and seasonably cold. A much colder air mass will arrive for the weekend. Parts of the region could struggle to reach freezing on Saturday and Sunday. Meanwhile, Nunavut experienced another day with near record and record high temperatures. High temperatures included: Eureka: -4° (just missed its daily record from 1985 by 0.2°C) Grise Fiord: 16° (old record: 9°, 1985) Iqaluit: 32° Kimmirut: 35° (old record: 23°, 2003) Pangnirtung: 30° (old record: 24°, 2007) Qikiqtarjuaq: 13° (old record: 12°, 2013) Resolute: 9° The abnormal warmth will likely continue in Nunavut through Saturday. 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 on the Washington, DC to Philadelphia area. A widespread significant snowfall (6" or above) still appears relatively unlikely. 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. Afterward, the evolution of the AO will determine whether potential for measurable snow events will continue into February. 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 -1.27 today. That is the first negative value since November 23, 2020 when the SOI was -7.83. Today, the preliminary Arctic Oscillation (AO) figure was -2.510. On January 20 the MJO was in Phase 6 at an amplitude of 0.682 (RMM). The January 19-adjusted amplitude was 0.424. 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 91% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.0°.

Morning thoughts... An area of clouds may move across parts of the region this morning, but the afternoon should be mostly sunny throughout the region. Temperatures will likely reach the lower to perhaps middle 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 42° Newark: 44° Philadelphia: 45° A strong cold front could bring another period of light snow or flurries on Friday.

A weak disturbance brought a round of light snow and snow showers across the region today. Snowfall amounts included: Allentown: Trace Bridgeport: Trace Islip: 0.2" New York City: Trace Newark: 0.3" Philadelphia: Trace The remainder of the week will be fair and seasonably cold. A much colder air mass will arrive for the weekend. Parts of the region could struggle to reach freezing on Saturday and Sunday. As Arctic blocking persists, next week could feature one or perhaps two more opportunities for snowfall, with the greatest risk focused on the January 25-28 timeframe. However, a widespread significant snowfall (6" or above) still appears relatively unlikely. A light or moderate snowfall is more likely. 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. Afterward, the evolution of the AO will determine whether potential for measurable snow events will continue into February. 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 -2.124. On January 19 the MJO was in Phase 5 at an amplitude of 0.425 (RMM). The January 18-adjusted amplitude was 0.638. 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 90% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.0°.

Three photos from this morning’s light snow: At 9:46, the sun is shining and the snow is rapidly disappearing.

Falling snow is always beautiful. Even light amounts are special.

Certainly, with a warming climate, moisture content has increased.

Morning thoughts... Following this morning’s light snow and flurries, it will become partly sunny. Temperatures will likely reach the lower 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 41° Newark: 43° Philadelphia: 43° A strong cold front could bring another period of light snow or flurries on Friday.

A quick video of this morning’s light snow:

Through the first 50 days of meteorological winter, the AO has averaged -1.900. It has been negative on 96% of days. It has been at or below -1.000 on 84% of days and at or below -2.000 on 50% of days. This blocking will likely continue into at least the closing days of January. Overnight into tomorrow morning, some snow showers and show flurries are likely. Parts of the region could pick up a coating of snow. There could be some additional opportunities for snowfall during the remainder of January, as blocking continues. However, significant or major snowstorms are probably not very likely. There continues to be ensemble support for some light snow or flurries in parts of the region during the January 21-23 timeframe during the passage of a strong cold front. Another timeframe highlighted by the ensembles is January 25-28. The latter period may have greater potential. However, neither period is likely to produce a significant snowfall (6" or above) for the Washington, DC to Boston corridor. AO-/PNA- patterns are typically not snowy. The frequency of measurable snowfall is just over 90% of climatology in Boston and Philadelphia and around 80% of climatology in New York City for the January 21-31, 1950-2020 period. The frequency of 2" or more daily snowfall was just above 90% of climatology for Philadelphia, but fell sharply to 50% of climatology in New York City and 65% of climatology in Boston. For daily snowfall amounts in excess of 2", the frequency fell sharply for Philadelphia. As a result, such patterns typically have produced significant snowstorms (6" or above snowfall) in the northern Middle Atlantic and southern New England regions during late January. The biggest snowfalls during an AO-/PNA- pattern during the January 20-31, 1950-2020 period were as follows: Boston: 7.3", January 21, 2011; New York City: 4.2", January 21, 2011; and, Philadelphia: 3.0", January 20, 2000. Afterward, the evolution of the AO will determine whether potential for measurable snow events will continue into February. 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 +22.99 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.012. On January 18 the MJO was in Phase 4 at an amplitude of 0.636 (RMM). The January 17-adjusted amplitude was 1.007. 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 87% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.2°.

A quick video clip from a short time ago:

There are some differences from the pattern shown in that late December post concerning January 1-20. In this case, there is model consensus that the EPO will go negative for a time before returning to positive levels. That opens the door for some snowfall potential for the Middle Atlantic region, but that’s not a good pattern for significant (6” or above) snowfalls. It will be interesting to see what the ECMWF shows today after the 0z run had a sizable snow event.

Morning thoughts... Today will be partly sunny. Temperatures will likely reach the lower 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 43° Newark: 44° Philadelphia: 45° A weak cold frontal passage could bring a few snow flurries tomorrow. A strong cold front could move across the region late in the week bringing a period of light snow or flurries.

No. It’s happened before. Here’s one discussion I posted concerning the January 1-20 period: https://www.americanwx.com/bb/topic/54083-december-2020-general-discussions-observations-thread/?do=findComment&comment=5773757 Through January 18, the January mean temperature is 37.9° in New York City.

New England could have some opportunities. The problem for the New York City area is the positioning of the block. It’s too far south (just as has been the case for much of this month). Of course, beyond two weeks the weeklies are little better than climatology.

Under partly sunny skies, the temperature rose into the lower and middle 40s across the region today. Tomorrow will be somewhat cooler. Meanwhile, parts of California experienced record warmth. High temperatures included: Oakland: 83° (old record: 67°, 2014) ***new January record*** Sacramento: 74° (old record: 69°, 2014) San Francisco: 74° (old record: 68°, 1948) ***tied January record*** Stockton: 78° (old record: 69°, 2009) ***new January record*** Oakland's previous earliest 80° temperature on record occurred on February 6, 2011 when the temperature reached 81°. That was Oakland's only 80° temperature on record in February. The previous earliest date on record for an 83° or above temperature was March 10, 2004 when the mercury reached 86°. Records at Oakland go back to 1948. During the second half of January, there will be some potential for snow events in the Middle Atlantic and southern New England regions, even as the forecast AO-/PNA- pattern is typically not a very snowy one. There continues to be ensemble support for some light snow or flurries in parts of the region during the January 21-23 timeframe during the passage of a strong cold front. Another timeframe highlighted by the ensembles is January 25-28. The latter period may have greater potential. However, neither period is likely to produce a significant snowfall (6" or above) for the Washington, DC to Boston corridor. AO-/PNA- patterns are typically not snowy. The frequency of measurable snowfall is just over 90% of climatology in Boston and Philadelphia and around 80% of climatology in New York City for the January 21-31, 1950-2020 period. The frequency of 2" or more daily snowfall was just above 90% of climatology for Philadelphia, but fell sharply to 50% of climatology in New York City and 65% of climatology in Boston. For daily snowfall amounts in excess of 2", the frequency fell sharply for Philadelphia. As a result, such patterns typically have produced significant snowstorms (6" or above snowfall) in the northern Middle Atlantic and southern New England regions during late January. The biggest snowfalls during an AO-/PNA- pattern during the January 20-31, 1950-2020 period were as follows: Boston: 7.3", January 21, 2011; New York City: 4.2", January 21, 2011; and, Philadelphia: 3.0", January 20, 2000. Afterward, the evolution of the AO will determine whether potential for measurable snow events will continue into February. 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 +22.66 today. Today, the preliminary Arctic Oscillation (AO) figure was -1.507. On January 17 the MJO was in Phase 4 at an amplitude of 1.001 (RMM). The January 16-adjusted amplitude was 1.145. 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 87% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.2°.

The 12z GFS notwithstanding, a 6” or greater snowfall in the forecast pattern is not very likely. Until one is within 48-72 hours and there is much greater model consensus, the base case remains a lighter accumulation scenario.

This week’s -1.3C figure of Region 4 was the coldest since the week centered around January 25, 2012 when the anomaly was also -1.3C.

We disagree. If you don’t wish to read a thread, you are not compelled to do so. I, for one, enjoy reading well-reasoned messages. Walt Drag’s posts are outstanding (as were his AFDs for those who recall his tenure at the National Weather Service). One can see both his expertise and passion for the weather.

In December New York City received 10.5” snow. In January, just a trace of snow has fallen. The lowest January snowfall figures following a December with 10.0” or more snow were 0.1” during winter 1933-34 and 0.3” during winter 1912-13. In addition, there have been 10 cases where January received less than 6.0” snow following a December with 10.0” or more snow. In 40% of cases, the remainder of winter saw less than 10.0” snow. In 50% of cases, the remainder of the snow season saw 20.0” or more snow. In all cases during which the remainder of winter picked up more than 10.0” snow, February saw 10.0” or more snow.

The information on social media concerning such events is typically quite poor. Although a lot is still not well understood, there is a large body of evidence that displacement events typically favor North America for cold while vortex-splitting events typically favor Eurasia with the cold. This SSW fell into the latter category. Parts of Asia and Europe have seen some severe cold. Much of North America hasn’t.

First, it’s weather. Second, there is educational value e.g., Walt Drag, explained, “A NAM TSection check is showing the cold pool aloft and the RH spike but only a smattering of measurable around the NYC forum so odds favor no occurrence of 0.1" snowfall in CP.” If one goes to Bufkit, among other places, one can better see what a top meteorologist sees and learn to evaluate potential events in a fashion that can only increase one’s own skill. Third, it’s fun and interesting to read such discussions, if one enjoys meteorology.