Weekend weather pattern at 500 mb may be quite volatile for the eastern US with a deep trough aloft and strong ridging across the west coast of Canada and the North Atlantic. Map courtesy ECMWF, Pivotal Weather

…very cold and active pattern next couple of weeks to include a weekend storm threat*

Meteorologist Paul Dorian

Overview

Winter will not loosen its grip anytime soon in the eastern US as it appears a very cold weather pattern will continue through at least the remainder of the month.  In addition, the overall pattern looks to be quite active as well with multiple storm threats possible and perhaps one by the early part of the upcoming weekend.

Colder-than-normal conditions will dominate in the eastern half of the nation during the 5-day period from January 22 – January 27 (days 6-10). Map courtesy NOAA, tropicaltidbits.com

Cold, stormy pattern

After a very mild month of December in much of the eastern US, the first half of January has been quite a different story with normal-to-slightly below-normal temperatures.  The second half of the month is looking quite a bit colder-than-normal and it may even include some extreme cold next week when temperatures could fall far below-normal for late January in portions of the northeastern states. During December, there was certainly some cold air masses around in North America, but they were generally bottled up across northwestern Canada and Alaska without a mechanism to transport them into the northern US.

Colder-than-normal conditions will dominate in the eastern half of the nation during the 5-day period from January 27 – February 01 (days 11-15). Map courtesy NOAA, tropicaltidbits.com

The overall upper air pattern, however, changed notably in the early part of this month to allow for the transport of cold air masses from northwest Canada into the central and eastern US. Specifically, a strong ridge of high pressure intensified and extended northward along the west coast of Canada and Alaska creating a strong northwest flow of air just to its east of the ridge axis.  It looks like this strong ridge will be quite persistent during the next couple of weeks.

Two teleconnection indices that support the idea of the western Canadian ridge holding its ground in coming days include the EPO (in negative territory) and the PNA (in a positive phase). Data courtesy ECMWF (EPO), Weather Bell Analytics (EPO), NOAA (PNA)

Two teleconnection indices that support the idea of this western ridge holding its ground and producing a cold overall pattern in the eastern US are known to meteorologists as the Eastern Pacific Oscillation (EPO) and the Pacific-North American (PNA).  When the EPO is consistently in a negative phase and the PNA is in a sustained positive phase during the winter season, a strong ridge of high pressure typically forms over the northeastern part of the Pacific Ocean and Alaska. This is indeed the likelihood for these teleconnection indices during the next couple of weeks as depicted by many recent computers forecast model runs.  If, in fact, the western ridge can expand far enough to the north, it can result in a “cross-polar” flow of air that can bring Siberian air masses across the North Pole and ultimately into the central and eastern US – not out of the question with this type of pattern over the next couple of weeks.

The next cold air outbreak to reach the eastern states on Thursday could be preceded by some snow as a wave forms along the cold frontal boundary zone. Map courtesy NOAA, tropicaltidbits.com

The next outbreak of cold air that reaches the eastern states will arrive on Thursday and it can be preceded by a period snow in parts as a wave of low pressure forms along the incoming frontal boundary zone.  Temperatures are likely to get progressively colder between Thursday and Friday with very cold conditions in place by week’s end.  Another cold air blast is destined to arrive into the eastern US early next week and this one may feature some extreme cold; especially, across the northeastern states.   

A storm threat exists for the early part of the upcoming weekend in parts of the eastern US with a strong upper-level wave of energy depicted here by the 12Z Euro for early Saturday morning. Map courtesy ECMWF, Pivotal Weather

In addition to the cold, it looks like the overall pattern will be quite active during the next couple of weeks in the eastern US with multiple storm threats on the table.  The two aforementioned upper-level ridges will be joined by a recurring upper-level trough over the eastern states which is likely to deepen appreciably this weekend. Another trough will likely form in the eastern part of the Pacific Ocean in coming days, and this is usually correlated well with an eastern US trough.  By the upcoming weekend, all of these pieces will be getting into place and indeed this can result in a storm system (or two) in the eastern states anywhere in the late Friday-to-Sunday time period.  Any storm that does form this weekend is likely to be followed by some very cold air early next week and additional cold air outbreaks are sure to follow.

Meteorologist Paul Dorian
Arcfield
arcfieldweather.com

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via Watts Up With That?

January 17, 2022

Winter Will not Loosen Its grip Anytime Soon in the Eastern US