Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
313 AM EST Mon Dec 12 2022

Valid 12Z Mon Dec 12 2022 - 12Z Wed Dec 14 2022

...Major storm system to bring significant, widespread weather hazards
from severe weather to blizzard conditions to the central U.S....

...Flash flooding and severe weather possible in the Plains Monday and
Lower Mississippi Valley Tuesday...

...Heavy snow, blizzard conditions, and freezing rain for the Northern and
Central Plains...

...Lingering snow and cold temperatures in the West through Tuesday...

A deep, upper-level trough over the West will shift slowly eastward
through the period. A strong, embedded vort max ejecting over the High
Plains as upper-level heights continue to fall ahead of the approaching
trough will lead to intense cyclogenesis in the lee of the Rockies. This
developing storm system will lead to numerous, widespread, and impactful
weather hazards in the heart of the country this week. Both flash flooding
and severe weather will be a risk in the Southern Plains east into the
Lower Mississippi Valley in the warm sector of the system. Anomalously
high moisture will surge northward ahead of a cold front sweeping eastward
late Monday evening. Increasing shear and cooling air aloft will provide
the necessary ingredients for a band of intense convection to develop
along the front north to south in the Central and Southern Plains. Some
intense downpours will be possible late Monday night/early Tuesday morning
that may lead to isolated instances of flash flooding, and there is a
Marginal Risk of excessive rainfall (level 1/4) in effect for a
north-south axis from southern Kansas south through western Oklahoma and
northwest Texas. In addition, there is a Slight Risk of severe weather
(level 2/5) from the Storm Prediction Center for western Kansas and the
Oklahoma Panhandle in vicinity of the surface low and beneath cooling air
aloft where strong wind shear and enough CAPE could produce a few
instances of severe hail, wind gusts, and a tornado or two.

The greater risk for severe weather and flash flooding will be on Tuesday
as height falls with the upper-level trough begin to spread further
eastward over the Plains and additional moisture surges northward from the
Gulf of Mexico contributing to higher CAPE values in the warm sector over
eastern Oklahoma and Texas and into the Lower Mississippi Valley. The line
of intense convection along the cold front will continue eastward with the
potential for additional isolated supercells to develop in the warm sector
ahead of the line. There is a Slight Risk of Excessive Rainfall (level
2/4) centered on the Lower Mississippi Valley as a couple rounds of
rainfall between the initial supercells and convective line will produce
rainfall totals between 1-2 inches, with localized areas of 2-4+ inches
leading to some scattered instances of flash flooding. In addition, there
is an Enhanced Risk of severe weather (level 3/5) for far northeastern
Texas and northern Louisiana where severe hail, winds, and tornadoes,
including the potential for a couple strong tornadoes, will accompany any
initial isolated supercells ahead of the line as well as embedded
supercells within the line. A broader Slight Risk (level 2/5) is in place
for eastern Texas, southern Arkansas, Louisiana, and southwestern
Mississippi.  

Meanwhile, cold air will continue to surge southward on the backside of
the low as warm air aloft surges northward leading to widespread wintry
precipitation and heavy snow for portions of the Northern and Central
Plains and Upper Midwest. Snow accumulations through Tuesday morning will
generally range between 6-12 inches, centered on the Northern High Plains.
The highest snow totals are currently forecast for western South Dakota
and northwestern Nebraska, where upwards of 18-24 inches is possible.
Winds will rapidly strengthen as the pressure gradient increases with the
deepening low pressure center, leading to the potential for blizzard
conditions in some locations. Currently, Blizzard Warnings are in effect
for portions of eastern Wyoming and central Nebraska, though the strong,
gusty winds upwards of 40-50 mph will still lead to the potential for
blowing snow and significant travel impacts across the region. Further
east, accumulating ice is also expected for portions of the eastern
Dakotas into the Upper Midwest. The current risk for the greatest ice
accumulations over a tenth of an inch is currently forecast for the
eastern Dakotas, southwestern Minnesota, and western Iowa. Some locations
in the Dakotas in particular will likely see both accumulating ice and
snow. Temperatures in the teens and 20s will spread southward from the
Northern High Plains Monday into the Central High Plains Tuesday.

Snow will continue in the west under the influence of the upper-level
trough as well as a Pacific cold front continuing through the Southwest
and Southern Rockies and a second frontal boundary slowly meandering
southward through the Central Rockies, Great Basin, and Pacific Northwest.
The snow will begin to taper off from west to east through the day
Tuesday, lingering longest in the Northern and Central Rockies. Additional
accumulations between 6-12 inches, locally higher, will be possible for
the mountain ranges of the central Great Basin, Central and Southern
Rockies, and Arizona. Lower elevations will continue to see a mix of some
lighter rain and snow, with little to no accumulations expected.
Temperatures will remain 10-20 degrees below average for this time of
year, with highs ranging from the 20s and 30s for the Great Basin and
Northern and Central Rockies, 40s for the Pacific Northwest and Southern
Rockies, and 50s for California and the Southwest.

Putnam

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