****A look ahead to the month of February…a polar vortex split, plenty of cold air around, and a very active pattern which includes the potential of significant icing in some cases****

There are signs for a polar vortex “split” by mid-month which would be supportive of cold air intrusions into the central and eastern states. Map courtesy ECMWF, Weather Bell Analytics, BAM Weather (X)

Overview

February is now underway and it looks like it will be a very active month with plenty of cold air around and is likely to feature a stratospheric polar vortex split that can impact US temperatures all the way into March. There should be plenty of opportunities for snow, ice and rain in the Mid-Atlantic region and Northeast US as we progress through the new month with just the next week or so likely to feature as many as three precipitation events. Another player on the field that will have to be monitored this month will be the occasional appearance of the Southeast US high pressure ridge – often seen during La Nina winters – and this enhances the possibility of generally warm conditions across the southern states and also chances for severe weather.

The teleconnection index known as the Arctic Oscillation (AO) slips into “negative” territory around mid-month which enhances the chance of “high-latitude blocking” in the atmosphere which, in turn, tends to favor cold air intrusions into the central and eastern US. Plot courtesy NOAA, ECMWF, BAM Weather (X)

Details

If you like winter storms then the next few weeks may be as good as it gets. The month of February is sure to be quite active with plenty of cold air around across the Canadian and US side of the pole. One of the features to watch in coming days in the upper part of the atmosphere will be the stratospheric polar vortex as there are signs that this may “split” by the time we get to mid-month. As such, there can be a “piece” of the polar vortex centered over southeastern Canada by mid-month, and this can be an important source of cold air for the Mid-Atlantic region and Northeast US from mid-February into March.

Teleconnection indices also support the idea of a favorable pattern for cold air intrusions into the eastern states by mid-month as both the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) slip into “negative” territory indicating that high-latitude blocking may become more prevalent. High-latitude blocking in the upper atmosphere tends to be a favorable setup for the transport of cold air masses from northern Canada into the central and eastern US. Another feature to watch will be the occasional emergence of a Southeast US high pressure ridge which is rather typical for La Nina winters. This could act as a warming influence at times up along the east coast into areas such as the southern Mid-Atlantic. In addition, a strong ridge of high pressure in the SE US can produce increasing warm and humid conditions across the southern states which, in turn, can enhance the chances for severe weather.

Somewhere in the circled region on this forecast map produced by the 00Z GFS, there can be some significant icing around the middle of this week along with accumulating snow (in blue) to the north of the “ice” zone and plain rain (in green) to the south. Map courtesy NOAA, tropicaltidbits.com

In terms of the outlook for precipitation, a look ahead to the 500 mb height anomaly pattern (featured in the video discussion) during the next few weeks shows numerous deep troughs and intense ridges across North America…all suggestive of quite an active pattern. In fact, in just the next week or so, it appears there will be as many as three opportunities for snow, ice and rain in the Mid-Atlantic region and Northeast US. The first such chance will come on Sunday night into early Monday across the northern Mid-Atlantic and Northeast US where snow is likely to be the predominate precipitation type and a few inches are on the table in many areas.

The teleconnection index known as the North Atlantic Oscillation (NAO) slips into “negative” territory around mid-month which enhances the chance of “high-latitude blocking” in the atmosphere which, in turn, tends to favor cold air intrusions into the central and eastern US. Plot courtesy NOAA, ECMWF, BAM Weather (X)

By mid-week, another opportunity will come for snow and rain in the Mid-Atlantic/Northeast US and this system may feature significant icing in parts of the area. The setup will include a cold frontal passage on Tuesday which will be followed by an influx of colder air by mid-week as moisture begins to gather over the Tennessee Valley. The cold air will likely be reluctant to give up its ground on Wednesday/Wednesday night as it will be anchored by strong high pressure centered over New England. As a result, surface temperatures may be slow to climb above freezing in portions of the northeastern states during this mid-week event potentially leading to a situation that will feature plenty of sleet and/or freezing rain. To the north of this “ice” zone, accumulating snow is likely, and to the south, plain rain will fall. The exact placement of that “battle zone” region between the cold (below-freezing) air to the north and warmer air to the south will have to wait a bit to be better determined, but the threat of significant icing is on the table for some.

Several signs point to colder-than-normal air overspreading the nation by mid-month as shown here by this Euro-AI 2-meter temperature forecast map for the period of February 11 to February 16. Map courtesy ECMWF, Weather Bell Analytics (Joe Bastardi, X)

Looking farther ahead, there have been rather persistent storm signals for a system next weekend that can have an impact on the Mid-Atlantic/Northeast US. This system could indeed produce some snow, ice and rain on from later Saturday into Super Bowl Sunday, February 9th, but the details on exact timing and precipitation types will have to wait until later this coming week. Even farther ahead, there may even be yet another storm system to deal with just a few days later around the 12th or 13th of February and, by this time, the cold air may have penetrated farther to the south compared with the prior storm systems.

The month of January likely ended up as the coldest since 1994 across the continental US. Map courtesy NOAA, Weather Bell Analytics

Bottom line…February is looking like a very interesting and active month with lots of storms, plenty of cold air around, and a likely important polar vortex “split” that can influence US temperatures all the way into March (take note Punxsutawney Phil). A final note…the month of January likely ended up as the coldest across the continental US since 1994.

Meteorologist Paul Dorian
Arcfield
arcfieldweather.com

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