Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
254 AM EST Wed Nov 24 2021

Valid 12Z Wed Nov 24 2021 - 12Z Fri Nov 26 2021

...Unsettled weather to track over the Middle Mississippi Valley Wednesday
night, then into the Great Lakes and Mid-South on Thanksgiving;
thunderstorms and Excessive Rainfall possible in the South Central U.S...

...Atmospheric River to deliver coastal and valley rain, high elevation
snow to the Pacific Northwest on Thanksgiving...

...Critical Risk of fire weather in Southern California today; brief warm
up in the East, cold Canadian air-mass returns by Black Friday...

A progressive jet stream pattern atop the Lower 48 makes for transient
temperature regimes and a fast paced storm system traversing the country
this Thanksgiving. An area of low pressure in the Upper Midwest this
morning will have no issues being stuck in traffic en route to its
destination in the Great Lakes this Thanksgiving. Conditions look mostly
dry today, but showers breaking out along and in front of its associated
cold front will expand from the Lower Great Lakes to South Texas Wednesday
night. By Thanksgiving morning, damp conditions are likely in the Ohio and
mid-Mississippi Valleys. Thunderstorms are also possible in southeast
Texas and in the Lower Mississippi Valley with a Marginal Risk for
Excessive Rainfall from far East Texas to the southern Texas border on
late Wednesday into Thursday. As the front marches east Thanksgiving
night, so will its precipitation shield, reaching the East Coast overnight
but already making a quick exit by Black Friday morning. Cold Canadian air
filtering behind the cold front then triggers the formation of lake effect
snow showers with generally light accumulations expected from the Upper
Great Lakes to the central Appalachians.

After a quiet day weather-wise on Wednesday thanks to a brief bubble of
high pressure aloft, the Pacific Northwest braces for yet another
Atmospheric River that makes its arrival Thanksgiving morning. Western
Washington can expect a prolonged barrage of rich Pacific moisture,
resulting in periods of moderate-to-heavy rainfall on Thanksgiving. A
Marginal Risk for Excessive Rainfall has been posted in parts of Western
Washington for Thanksgiving. Due to unusually high snow levels, only the
highest elevations of the northern Cascades are likely to witness
measurable snowfall. Aside from spotty showers and light snowfall
accumulations in the Rockies this morning, the vast majority of the West
will enjoy an otherwise dry pattern through Thanksgiving and into Black
Friday thanks to a strengthening dome of upper level high pressure
stretching from California to the Great Plains.

Elsewhere, much of the Southern California coast is under Red Flag
Warnings through Thanksgiving due to ongoing Santa Ana winds. The Storm
Prediction Center has also placed the higher elevations of Southern
California under a Critical Risk for fire weather conditions today and for
Thanksgiving. Temperature-wise, the East Coast can expect one more day of
abnormally chilly temperatures today, but a brief warm-up arrives on
Thanksgiving ahead of an approaching cold front. This cold front, the one
responsible for the unsettled weather tracking across the East during the
short term period, is set to bring another intrusion of cold Canadian air
into the Midwest and Southern Plains on Thanksgiving. This surge of colder
temperatures reaches the East Coast and Deep South just in time for the
start of the upcoming weekend. Meanwhile in the West, the aforementioned
ridge of high pressure will lead to a warm-up along the West Coast on
Thanksgiving, then quickly expanding into the Rockies and Great Plains by
Black Friday.

Mullinax

Graphics are available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php