Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
1225 PM EST Sat Dec 10 2022

Valid 00Z Sun Dec 11 2022 - 00Z Tue Dec 13 2022

...Major storm system will continue to bring heavy mountain snow and
coastal rain to the West this weekend...

...Wintry precipitation spreading from the Great Lakes region today into
the Northeast on Sunday...

...Episodes of moderate to heavy rainfall possible as showers and
thunderstorms continue for the South...

A deepening trough aloft and frontal system at the surface moving through
the West will continue to spread heavy snow in the mountains, a wintry mix
for inland valleys, and heavy coastal rain across the region this weekend.
An impressive stream of moisture from the Pacific associated with an
atmospheric river will help to promote both high rainfall and snowfall
rates as well as totals. The impacts will be widespread from north to
south with numerous winter weather-related advisories in effect. Starting
across the Pacific Northwest, Northern Rockies, Great Basin, and
California, snowfall totals through the weekend will generally range
between 12-24 inches, locally higher, for higher elevations in the
mountains. The heaviest snowfall is expected for the Sierra Nevada with
several feet forecast. Some snow will likely mix with rain for lower
elevation, valley locations, though any accumulations should remain very
light. Snow will also spread into the mountains of the Central Rockies and
Arizona Sunday and Sunday night, with totals of 6-12 inches, locally
higher amounts, anticipated through early Monday morning. For
rainfall-related impacts, there is a Slight Risk of Excessive Rainfall
(level 2/4) for the central California coast tonight and for southern
California around the greater Los Angeles and San Diego metropolitan areas
on Sunday. Rainfall totals of 2-4 inches, locally higher, as well as the
potential for heavier rainfall rates over 0.5 inches per hour may lead to
some scattered instances of flooding. Temperatures will also remain cool
under the influence of the upper-level low, particularly across
California, with forecast highs running 10-20 degrees below average.

A surface wave moving quickly through the Upper Great Lakes today will
bring the risk of some freezing drizzle as well as snow showers with some
light accumulations possible. A frontal system will move into the
Northeast on Sunday with some snow expected for southern New England, the
interior Northeast, and the central Appalachians. Moderate snow totals
between 3-4 inches are possible inland for higher elevation locations like
the Berkshires and Catskills, and 1-2 inches are possible further south
into central Pennsylvania. Precipitation should remain as rain closer to
the coast, though some snow will likely mix in for southern New England. 
High temperatures will be a bit below normal for the East Coast with 30s
and 40s for the Northeast and 50s in the Carolinas. Temperatures will warm
up a bit behind the system in the Midwest on Sunday, with highs ranging
from the 30s in the Upper Great Lakes to the 50s in the Middle Mississippi
and Ohio Valleys.

Small-scale disturbances along a frontal boundary moving through the South
will continue the chance for showers and thunderstorms in the region. The
heaviest rainfall is expected tonight along a northeast to southwest axis
from the Mid-South through northern Texas. Storms here may redevelop and
move over the same locations in vicinity of the surface front. A Marginal
Risk of Excessive Rainfall (level 1/4) is in effect as locally higher
rainfall totals over 2 inches and rainfall rates of 1 inch may result in a
couple isolated instances of flash flooding, especially in urban areas.
High temperatures will cool closer to normal on Sunday following the
frontal passage with mid-60s to mid-70s expected.

Putnam/Kebede

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