Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
350 AM EST Wed Dec 14 2022

Valid 12Z Wed Dec 14 2022 - 12Z Fri Dec 16 2022

...Major, significant storm system continues to bring heavy snow and
blizzard conditions to the Northern Plains and Upper Midwest...

...Winter ramps up for the Interior Northeast and Northern/Central
Appalachians Thursday with accumulating snow and freezing rain likely...

...The risk for flash flooding and severe weather continues for the South
Wednesday...

...Lingering snow showers continue for the Northern and Central Rockies as
temperatures remain below normal across the West...

A major, significant storm system already producing hazards ranging from
blizzard conditions to flash flooding continues for the central and
eastern U.S.  The primary, deep surface cyclone will move northeastward
from the Plains into the Upper Midwest as waves of upper-level energy
swing around a deep closed low aloft. An occluding surface front will
progress northwestward over the Midwest as a cold front pushes eastward
through the South. Beginning in the north, widespread heavy snow continues
across the Northern Plains into the Upper Midwest. Additional
accumulations through Thursday morning will range between 8-12 inches,
locally higher, for portions of the Upper Midwest in the vicinity of Lake
Superior, the Northern High Plains, and portions of the eastern Dakotas.
Additional snowfall between 4-8 inches will be possible elsewhere in the
Northern Plains and Upper Midwest. The highest additional totals are most
likely in the Arrowhead of Minnesota, where upwards of 18-24+ inches is
forecast. Many locations in the Northern High Plains that have already
seen snowfall the past day will end with storm total snowfall between
20-30 inches as well. In addition to the heavy snow, strong, gusty
northerly winds upwards of 45-55 mph due to the tight pressure gradient
between the deep surface low and the Rockies will continue to produce
blizzard conditions and have significant travel impacts. Most roads,
including the major interstates I-80, I-90, and I-94, remain closed
through the Northern and Central High Plains. High temperatures will
remain bitterly cold in the Northern and Central High Plains, with highs
in the teens and 20s and wind chills dipping below zero.

Precipiation chances will begin to expand to the East Coast on Thursday as
the upper-level low and associated surface fronts move eastward, with a
coastal low forming near the Carolinas and moving up the coast. Winter
Storm Watches have been issued for portions of the Interior Northeast
along the Northern and Central Appalachians. Freezing rain totals between
0.1-.25 inches, locally higher, will be possible in the Central
Appalachians of western Virginia, eastern West Virginia, the Maryland
Panhandle, and central/Western Pennsylvania. The precipitation will
transition to more of a snow threat further north into New York, with 4-8
inches, locally higher at elevation in the mountains, possible through
Thursday morning. Portions of Pennsylvania will be most likely to see a
mix of freezing rain and snow. The snowfall will continue and move further
north into New England by Friday. Closer to the coast, although
precipitation will remain mostly rain, some light but impactful freezing
rain, sleet, and snow may mix in during the Thursday morning commute along
the I-95 corridor. Otherwise, moderate to heavy rainfall will continue
through the day with totals upwards of 1-2 inches for the Mid-Atlantic.
Rainrates should remain steady enough throughout the day to preclude any
risk of flash flooding. High temperatures will remain in the 30s and 40s
for the region.

Further south in the warm sector of the system, the threat for flash
flooding and severe weather will accompany a line of thunderstorms pushing
ahead of the cold front across the South and southern portions of the Ohio
Valley. There is a broad Slight Risk of Excessive Rainfall in effect from
the Lower Mississippi Valley northeastward through the Tennessee Valley
and into portions of the Ohio Valley and Southern Appalachians. The
tendency for heavy downpours within an expanding line of convection to
move roughly in line with the cold front prolonging rainfall duration, in
addition to any pre-frontal convection, will lead to a broad swath of 1-3
inches of rain. There is a more concentrated Moderate Risk (level 3/4)
from southeastern Louisiana northeastward through southern Mississippi and
into west-central Alabama where there is more confidence for rainfall
totals of 3+ inches, and scattered to numerous instances of flash flooding
will be a concern. There is also an Enhanced Risk of severe weather (level
3/5) for the central Gulf Coast where warmer temperatures and higher Gulf
moisture flowing northward near the coast will lead to sufficient CAPE for
additional severe thunderstorm development. Damaging winds and tornadoes
will be the primary threats, with strong low-level shear leading to the
risk for a couple strong tornadoes. For Thursday, there is a Slight Risk
of severe thunderstorms (level 2/5) for far southeastern South Carolina
and Georgia as well as portions of the northern/central Florida Peninsula
and Big Bend as a few supercells ahead of the line as well as storms
within the line will continue to carry the risk for some strong winds and
brief tornadoes.

In the West, snow showers will linger over the Northern and Central
Rockies as well as the Northern Great Basin. High temperatures will remain
10-20 degrees below normal under the influence of the deep upper-level low
and general northerly flow. Highs will range between the 20s and 30s for
the Northern and Central Rockies and Great Basin, the 40s and 50s for the
Pacific Northwest and the Southern Rockies, and the 50s to low 60s for
California and the Desert Southwest. 

Putnam

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