Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
257 AM EST Thu Nov 25 2021

Valid 12Z Thu Nov 25 2021 - 12Z Sat Nov 27 2021

...Developing storm system to produce widespread showers throughout most
of the eastern third of the U.S. this Thanksgiving; thunderstorms and
Excessive Rainfall possible in southeast Texas; heavy snow likely in
northern New England...

...Atmospheric River to generate moderate-to-heavy rainfall in the Pacific
Northwest today...

...Strong Santa Ana wind event to cause threatening fire weather
conditions and destructive wind gusts; cooler temperatures return the East
on Black Friday, warm-up continues out West...

The primary weather maker this Thanksgiving Day is an area of low pressure
tracking through the Upper Great Lakes. Its trailing cold front is causing
numerous showers to develop from the Great Lakes and Mid-South to the
western Gulf Coast. Southeast Texas may observe enough instability within
the atmosphere to trigger thunderstorms, some of which could produce
locally Excessive Rainfall rates. By Thanksgiving night, showers are
forecast to reach the East Coast while colder temperatures funneling
behind the cold front initiate lake effect snow bands across parts of the
eastern Great Lakes and into the interior northern Mid-Atlantic. This
storm system is set to strengthen quickly during the day Friday as an
upper level low deepens over the Northeast. On the northern side of the
upper low, periods of snow are expected with the heaviest totals taking
shape over northern New England. Latest forecast totals show over six
inches in the Adirondack, Green and White Mountains with as much as a foot
of snow possible. Travelers in northern New England may contend with icy
and treacherous conditions, especially on untreated surfaces late Friday
into Saturday morning.

In the West, a new Atmospheric River containing rich subtropical Pacific
moisture takes aim at the Pacific Northwest today. A prolonged stretch of
moderate-to-heavy rainfall combined with rapid snow melt could lead to
excess runoff. This may result quickly rising creeks and streams, making
localized flooding a possibility in parts of western Washington. Locally
heavy rainfall is also possible in far northwestern Oregon, but the
heaviest rainfall totals (1 to 3 inches) are most likes to occur in the
Olympics and northern Cascades. High pressure building in atop the
Northwest on Friday will provide a brief break in the action, but another
round of heavy rain arrives late Saturday. 

In contrast to their neighbors in the Northwest, residents in Southern
California are dealing with Santa Ana winds. High Wind Warnings have been
posted along the mountain ranges with Wind Advisories near the coast. Wide
spread wind gusts of 35 to 50 mph are expected with damaging gusts of 70
mph are possible in the mountains and foothills. In addition, dangerously
low humidity levels support a hazardous environment for fire weather
conditions. Red Flag Warnings and a Critical Risk for hazardous fire
weather conditions, issued by the Storm Prediction Center, were issued for
much of the Southern California mountains and foothills. The Santa Ana
wind event today should wind down to an extent by Thanksgiving night but
an Elevated Risk for favorable fire weather conditions looks to persist
into Black Friday. Temperature-wise, a warm-up in the East today will be
short lived as a cold front ushers in yet another shot of cold Canadian
air on Friday. December-like temperatures look to stick around in the
Mid-Atlantic and New England on Saturday. Meanwhile, a building upper
level ridge over the western third of the Lower 48 means temperatures will
warm-up incrementally each day to close out the week and into the upcoming
weekend.

Mullinax

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