Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EST Fri Dec 01 2023

Valid 00Z Sat Dec 02 2023 - 00Z Mon Dec 04 2023

...Prolonged winter storm with multi-day atmospheric river activity will
impact the Northwest with significant mountain snowfall and heavy rains...

...Unsettled weather forecast across the eastern third of the country with
heavy rain potential along the Gulf Coast and Southeast, while wintry
weather is expected from parts of the Midwest and Great Lakes to northern
New England...

Meteorological winter is off to a fast and active start across much of the
Pacific Northwest, Great Basin, and the Rockies as plentiful moisture
streams inland from the Pacific Ocean over at least the next few days.
After seeing initially more modest atmospheric river activity today
through Saturday, with generally moderate precipitation, the strongest
atmospheric river related to the series of cold fronts advancing inland
off the Pacific Ocean will be on Sunday. This will drive locally
significant impacts from heavy mountain snow and heavy rainfall. Total
rainfall amounts through this weekend are expected to approach 5 to 10
inches along the coastal ranges of western Washington and Oregon, with
several inches of rain also expected for places such as Portland, OR and
Seattle, WA. Meanwhile, heavy snowfall adding up to at least a few feet is
expected across the Cascades, including many mountain passes. Travel will
be difficult to hazardous due to both heavy snow and blowing snow. Snow
levels are expected to increase by Saturday night and throughout the day
on Sunday as warmer air arrives, leading to heavy rain on top of the
snowpack throughout the Cascades. This combination of heavy rain and
snowmelt on Sunday will likely produce minor to moderate river flooding.

The heavy snowfall threat will also extend well east into the mountainous
terrain of the Great Basin and Rockies as Pacific moisture spilling out of
the Pacific Northwest reaches the windward slopes of the Intermountain
Region. The higher terrain of Idaho, western Montana, northern Utah,
northwest Wyoming and northwest Colorado will see locally as much as 1 to
3 feet of snow by early Monday. Widespread Winter Storm Warnings and
Winter Weather Advisories have been issued for many areas of these areas
in addition to the Pacific Northwest.

Elsewhere across the country, a strong deep layer axis of moisture and
warmer air crossing the Mid-South, Gulf Coast states, and lifting up along
the Eastern Seaboard will foster generally unsettled and mild weather for
these areas for the first weekend of December. An initial weak storm
system is forecast to progress across the Ohio Valley and the Lower Great
Lakes region tonight through midday Saturday as another developing system
right on its heels enters the Great Lakes on Sunday. Overall, light rain
is expected across the Ohio Valley, Appalachians, Northeast, and
Mid-Atlantic. However, elevated atmospheric moisture content and
instability may lead to locally heavy rainfall and thunderstorms along
portions of the central and eastern Gulf Coast through this evening and
overnight. This threat of heavy rainfall will advance into parts of the
Southeast on Saturday out ahead of a very slow-moving front, with the
Florida Panhandle in particular potentially seeing sufficient rainfall for
some flooding concerns. The Weather Prediction Center has highlighted
portions of this area in a Slight Risk of excessive rainfall for Saturday
and Saturday night. Farther north, wintry weather is expected on the
northern periphery of the precipitation shield as cold air remains in
place due to a stretched out high pressure system extending into southeast
Canada. Mostly light and localized areas of snow may impact some areas the
Lower Michigan. Heavier snow is possible across northern New England by
Monday as a stronger storm system begins to organize new coastal New
England.

Snell/Orrison

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