***One of the coldest starts to December in many years with a “Siberian” connection…western US snows…interior Northeast snows…Great Lakes snow machine turns on full throttle***

The upcoming cold wave will feature colder-than-normal air penetration all the way into the Gulf of Mexico including the central and southern parts of Florida. This “backward trajectory” map suggests some of the air coming into the US in coming days will have originated over Siberia…i.e., on the other side of the North Pole. Map courtesy NOAA

Overview

One of the biggest weather stories going forward is the cold wave that is coming to much of the nation beginning late this week and likely continuing for much of the first couple weeks of December. In fact, this will likely be one of the coldest starts to the month of December in many years and it will have a “Siberian” connection.

Before we get to the cold wave, there will be a lot of weather to go through across much of the nation with significant snowfall in some areas. Low pressure is currently pushing eastward across the higher elevations of the western US resulting in substantial snow accumulations from the Sierra Nevada Mountains of eastern California to the Colorado Rockies. Some of these locations will end up with snow totals on the order of 1-2 feet before this low spills out into the middle of the nation at mid-week.

From there, this low pressure system will move rather quickly across the Tennessee Valley on Wednesday night and to the southern New England coastline by mid-day Thursday. As a result, rain is likely to reach the DC-to-Philly-to-NYC corridor by late Wednesday night and continue into Thursday (Thanksgiving Day). Farther to the north, accumulating snow is likely to fall from early Thursday into early Friday across interior, higher elevation locations of northern PA, upstate NY and interior New England with several inches on the table.

Following the departure of the low pressure system to the western Atlantic, a northwesterly flow of air will develop across the northeastern quadrant of the nation bringing much colder-than-normal air from Canada into the Great Lakes, Mid-Atlantic, and Northeast US. The “Great Lakes snow machine” will get turned on full throttle with the much colder-than-normal air flowing over the still relatively warm waters of the Great Lakes from later Friday into Saturday and there is likely to be much more in the way of “lake-effect” snow activity during this upcoming cold wave.

Teleconnection indices shown on this forecast map of 5-day mean 500 mb height anomaly are suggestive of a wintry pattern for much of the nation. The combination of high-latitude blocking, ridging along the west coasts of the US, Canada and Alaska, and a deep trough centered over the east coast will allow for the transport of cold air masses from northwestern Canada into the US. In fact, this pattern can result in “cross-polar” flow which will allow for “Siberia-originated” air to make its way from the other side of the North Pole to North America. Map courtesy ECMWF, stormvistawxmodels.com

One of the coldest starts to December in many years with a Siberian connection

An overall very wintry weather pattern is shaping up for much of the central and eastern US beginning late this week and likely continuing through much of the first couple weeks of the new month. In fact, this should turn out to be one of the coldest starts to the month December in many years and it’ll have a Siberian connection. The upper air pattern will favor the transport of cold air masses from northwestern Canada into the US and there are signs for “cross polar” flow to develop which would allow for the transport of very cold “Siberia-originated” air from the Asian side of the North Pole to the North America continent.

This upcoming cold wave will likely feature some well below-normal air all the way down to the Gulf coast. This forecast map for late next Thursday night, December 6th, is indicative of the penetration of this cold air intrusion. Map courtesy ECMWF, weathermodels.com, Dr. Ryan Maue (X)

The upper-atmosphere pattern should feature strong ridging over Alaska (-EPO) which can transport Siberia-originated air into North America and a strong ridge over the west coasts of Canada and the US (+PNA) which can then help to move the cold air masses from northwestern Canada into the US, and, in some cases, all the way down to the Gulf coast including through central and southern Florida. The upper air pattern will also feature continued high-latitude blocking high pressure over northeastern Canada and Greenland (“west-based” -NAO) and this will act to keep this cold weather pattern locked in place for some time…at least until the second week of December.

The mountains from the Sierra Nevada of eastern California to the Colorado Rockies will get substantial snowfall between now and tomorrow night as low pressure cross the interior western US. Map courtesy NOAA, tropicaltidbits.com

Western US mountain snows

Low pressure continues to push eastward today across the interior western US and it is bringing lots of pacific Ocean moisture along with the ride. Significant snow continues to pile up across the Sierran Nevada Mountains of eastern California and it will extend all the way to the Colorado Rockies by tomorrow…some spots in these higher elevation locations will end up with 1-2 feet of snow by later tomorrow...good news for skiers in that part of the nation.

The DC-to-Philly-to-NYC corridor is going to get rain from late tomorrow night into Thursday, but there can be several inches of snow across portions of upstate PA, upstate NY and interior New England. Map courtesy NOAA, tropicaltidbits.com

Rain along I-95 corridor later tomorrow night into Thursday with interior, higher elevation snows

The low pressure system that is bringing substantial snows to the mountains out across the western US will spill out into the nation’s heartland at mid-week and then move rather quickly from the Tennessee Valley on Wednesday night to the southern New England coastline by mid-day Thursday (Thanksgiving Day). Rain is likely to be the predominate precipitation type in the DC-to-Philly-to-NYC corridor from late Wednesday into Thursday which certainly can put a damper on the annual Thanksgiving Day parade in New York City.

Farther north, snow is likely to fall from the northern third of PA to upstate NY to interior New England between early Thursday and early Friday and 6+ inches could pile up in some of those higher elevation locations. By late Friday, the departing low pressure system will intensify over the western Atlantic Ocean and broad northwesterly flow will develop on its backside.

The water temperatures of the Great Lakes are still relatively warm and this will set up a classic lake-effect snow event late this week and upcoming weekend with much colder-than-normal air passing overhead. The combination of cold NW flow above the relatively warm lake waters destabilizes the atmosphere and moisture is squeezed out in the form of snow, heavy at times. Map courtesy NOAA/ERL

Great Lakes snow machine gets turned on full throttle 

A long duration Great Lakes snow event is setting up to begin at the end of the week with substantial snow accumulations on the table in many spots just downstream of the five lakes. This looks like the classic setup for significant “lake-effect” snow as very cold air will flow over the still relatively warm (and unfrozen) waters of the Great Lakes for an extended period of time.

The “Great Lakes snow machine” gets activated on Friday and it may not shut down for quite awhile. Additional lake-effect snow events are likely during this upcoming cold wave which may last into the second week of December. Map courtesy NOAA, weathermodels.com

In fact, lake effect snows can begin later Friday and last all the way through the upcoming weekend and this long duration “lake-effect” snow event may not be the only one as additional chances are likely to take place during this upcoming cold wave that can extend into the second week of December.  

Meteorologist Paul Dorian
Arcfield
arcfieldweather.com

Follow us on Facebook, Twitter, YouTube

Video discussion: