Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EST Sat Dec 02 2023

Valid 12Z Sat Dec 02 2023 - 12Z Mon Dec 04 2023

...A multi-day atmospheric river event will impact the Northwest with
significant mountain snowfall and heavy rain this weekend...

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

...Generally milder than normal temperatures expected for across most of
the Lower 48...

The first weekend of December is shaping up to be an active one in the
West thanks to a series of atmospheric rivers directing copious amounts of
Pacific moisture into the Pacific Northwest and the Rockies. The next
storm in a series of storm systems arrived this morning, inflicting more
heavy mountain snow in the Olympics and Cascades that will continue
throughout the day. Meanwhile, the same moisture source will push inland
towards the Rockies Saturday and into Saturday night. As a result, heavy
mountain snow is on tap from eastern Oregon and the northern Rockies on
south to the Wasatch Range in Utah and the Colorado Rockies. By Sunday,
the next storm system will track farther north towards British Columbia.
This storm system's warm front lifts north through western Washington and
Oregon on Sunday, forcing snow levels to rise sharply and force most of
the Cascades and Olympics to switch over to heavy rain. This combination
of heavy rain atop a deep snowpack may lead to minor and moderate river
flooding, as well as possible flash flooding, into early next week. WPC
has issued a Slight Risk for Excessive Rainfall on Sunday for portions of
western Oregon, while a Marginal Risk extends north from the far northern
California coast to Washington's Cascade and Olympic Ranges. As much as 5
to 10 inches of rainfall are forecast along the coast of Oregon, while as
much as several feet of snow accumulate in the higher terrain and passes
of the Cascades. The northern and central Rockies can also expect heavy
snow with some areas seeing 1-3 feet through the weekend. The Winter Storm
Severity Index (WSSI) shows Major Impacts are possible in the highest
elevations of the Pacific Northwest and the Rockies, likely causing
hazardous to even impossible travel conditions in these impacted areas.

Farther east, a pair of storm systems will lead to wet and wintry weather
across portions the eastern third of the CONUS. Along the Gulf Coast, low
pressure tapping into rich Gulf of Mexico moisture is set to ignite
strong-to-severe thunderstorms from southern Louisiana to the Florida
Panhandle. There are Slight Risks for both severe storms and Excessive
Rainfall in portions of these areas today with severe storms more likely
to contain damaging wind gusts and/or tornadoes. Farther north, showers
will envelope the Mid-Atlantic and both the Ohio and Tennessee Valleys
Saturday afternoon and into Saturday night. By Sunday morning, a new storm
system tracking into the Great Lakes will be responsible for periods of
light rain and snow from the Midwest to the northern Great Lakes. Farther
east, another developing area of low pressure along the Northeast coast
looks to form and produce periods of rain along the I-95 corridor during
the day on Sunday. In northern New England, precipitation will fall in the
form of snow Sunday afternoon and into Sunday night. Snow looks to fall
heavily at times in the Adirondacks, the Green and White mountains, and
into northern Maine. Latest WPC probabilistic forecasts shows a high
chance (greater than 70%) for snowfall totals over 6 inches through Sunday
night from central New Hampshire to both northern and central Maine. The
latest WSSI shows Moderate Impacts from east-central New Hampshire into
central Maine, indicating snowfall here will be capable of causing
disruptions to daily life. This includes hazardous driving conditions and
potential closures and travel delays.

Temperature-wise, much of the Lower 48 will witness seasonal to milder
than normal conditions, particularly east of the Rockies. The coolest
temperatures versus normal will be experienced in the Rockies. Back in the
Southeast, record warm morning lows are forecast from South Florida to the
Mid-Atlantic coast on Sunday.

Mullinax


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