Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EST Wed Dec 21 2022

Valid 00Z Thu Dec 22 2022 - 00Z Sat Dec 24 2022

...Powerful winter storm to produce a multitude of weather hazards across
the central and eastern United States through the end of the week...

...Bitter cold and life-threatening wind chills over the northern Plains
to surge southward this evening and swing towards the East Coast on
Friday...

...Significant freezing rain possible across parts of western Oregon and
Washington beginning Thursday night...

A significant and disruptive storm system is forecast to produce a
multitude of weather hazards over the next several days, as heavy
snowfall, strong winds, and dangerously cold temperatures span from the
Intermountain West through the Plains, the Great Lakes, and the central
Appalachians. At the forefront of the active weather pattern is a
dangerous and record-breaking cold air mass in the wake of strong arctic
cold front diving southward across the central Plains today and the
southern Plains by late Thursday. Behind the front, temperatures across
the Intermountain West and northern High Plains have plummeted 25 - 35
degrees F in just a few hours, with widespread minus 10 to minus 20
readings across the region. This, combined with sustained winds of 20 - 30
mph and higher wind gusts of up to 60 mph, have and will continue to lead
to wind chills as low as minus 40 degrees across a large swath of the
Intermountain West and northern/central Plains, with more localized areas
of minus 50 to minus 70 possible through the end of the week. Wind chills
of this magnitude can cause frostbite in less than 5 minutes if
precautions are not taken, with hypothermia and death also possible from
prolonged exposure to the cold. Livestock interests will also be severely
impacted and dangers could be exacerbated if power outages occur.
Consequently, widespread Wind Chill Warnings have been issued for areas
spanning from eastern Washington State, through the Intermountain West,
central/northern Plains, and Tennesse Valley, with additional Wind Chill
Watches and Advisories covering areas as far south as the southern Plains
and Gulf Coast. As the arctic front dives southward through the overnight
hours and Thursday, daytime temperatures across the central Plains will
struggle to get above 0 degrees, while areas further south in Texas and
the Gulf Coast will experience temperatures in the single digits and teens
Thursday evening. Furthermore, snow squalls, or a brief burst of moderate
to heavy snow (1 to 2 hours), are likely to occur immediately behind the
arctic front from the Intermountain West, to the central Plains, Ohio
Valley, Mid-Atlantic, and Northeast. Developing snow squalls could lead to
extremely hazardous travel conditions at times, as they will be
accompanied by gusts to 40 mph, potentially creating sudden whiteout
conditions.

Another hazardous facet of the system will be a deepening low-pressure
center that forms along the frontal boundary this evening and rapidly
strengthens as it tracks eastward across the Midwest and Great Lakes on
Thursday. This storm system is likely to produce widespread
light-to-moderate snowfall from the Midwest to the Great Lakes and
Interior Northeast, with a brief burst of snow also possible into the
Ohio/Tennessee Valleys and northern Mid-Atlantic immediately following the
cold frontal passage. The heaviest snowfall, with amounts potentially
exceeding a foot, is anticipated to occur over the Great Lakes between
tonight and Friday, especially along westward and northward-facing
lakefronts, as lake-enhanced snowfall along with moisture wrapped around
the low will help aid in the locally heavy totals. Combined with the
snowfall, very strong winds will also accompany the system as a very tight
pressure gradient develops between the low over the Great Lakes and the
strong high-pressure system over the northern Plains. Heavy snowfall rates
of 1-2"/hour, along with wind gusts of over 50 mph will result in
near-zero visibility and considerable blowing and drifting of snow. This
will lead to dangerous, to at times impossible, land and air travel
leading up to the holiday weekend. The combination of heavy snow and
strong wind gusts could lead to significant infrastructure impacts,
including scattered tree damage and power outages. Residents across the
aforementioned regions are advised to make final preparations as soon as
possible and check on family and friends during the storm in case of an
emergency.

Further east, in the warm sector of the strengthening storm system,
moisture surging northward ahead of a center of low-pressure and
associated coastal boundary situated off the Southeast coast will lead to
moderate to heavy rainfall across the Southeast and Mid-Atlantic on
Thursday with rainfall totals of 1-3" possible. As the low-pressure system
tracks northward Thursday evening, strong southerly winds ahead of the
center of low-pressure, combined with the new moon-tide cycle, may lead to
dangerous coastal flooding from northern New Jersey to northeast
Massachusetts. Furthermore, heavy rain over a fresh snowpack could also
create scattered flooding concerns for parts of Vermont and Maine on
Friday, which has prompted a Slight Risk (level 2/4) of Excessive Rainfall
to be issued. Lastly, at the leading edge of the northward surging
moisture over the Mid-Atlantic during the first half of the day on
Thursday, light freezing rain and locally heavy snowfall could impact
parts of the central Appalachians. A lingering cold air damming
environment will likely keep this brief punch of wintry weather confined
to the higher terrain and near the Blue Ridge mountains, but could still
lead to snowfall totals of up to six inches in some spots. Moreover, on
Friday, as the arctic cold front races eastward across the Mid-Atlantic
and Northeast, temperatures will plunge from the mid-to-upper 50s to the
10s and 20s in a matter of hours, which could lead to a rapid flash freeze
of wet pavement and surfaces from antecedent rainfall.

Looking forward, the next storm system to impact the Pacific Northwest
will spread precipitation and gusty winds onshore by late Thursday ahead
of an approaching warm front. After initially starting as snow, sleet and
freezing rain is likely to develop and could linger for an extended amount
of time over parts of western Washington and northwestern Oregon. This
changeover to freezing rain is due to a dense arctic airmass remaining in
place at the surface while warmer air surges over the region in the upper
levels. Localized ice accretion of a half inch could create the potential
for dangerous travel conditions and scattered power outages.


Russell/Snell

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