Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EST Sat Dec 24 2022

Valid 00Z Sun Dec 25 2022 - 00Z Tue Dec 27 2022

...Arctic air enveloping much of the eastern two-thirds of the U.S. will
be slow to moderate...

...Lake-effect snows downwind from Great Lakes with locally blizzard
conditions will slowly become less intense...

...Heavy mixed precipitation to impact the Pacific Northwest followed by
snow across the northern Plains to the Midwest...

A large and robust low pressure system lifting into southeastern Canada is
forecast to gradually weaken and move rather slowly during the next couple
of days.  Blustery west to northwesterly winds behind this expansive
system will continue to direct arctic air from central Canada down into
much of the eastern two-thirds of the country, with only slow moderation
of temperatures through the rest of the weekend into Monday.  As the
frigid air continues to flow across the warm waters of the Great Lakes
under the tight pressure gradient on the back side of the low pressure
system, lake-effect snows with locally blizzard conditions are expected to
continue into tonight.  Enhancement from the ice-free Great Lakes will aid
in producing 2-4 foot totals in favored snow belts.  Conditions should
gradually improve with time as the low pressure system is forecast to
slowly weaken.  However, the system will be slow to exit southeastern
Canada, resulting in strong gusty winds initially up to 60 mph to
accompany the snow downwind from the Great Lakes.  Traveling in these
conditions will be extremely dangerous in the most intense snowbands.

The Arctic blast that has been felt across the eastern two-thirds of the
country will be slow to moderate through the rest of the holiday weekend
and into Monday.  The life-threatening cold temperatures and in
combination with dangerous wind chills will create a potentially
life-threatening hazard for travelers that become stranded, individuals
that work outside, livestock and domestic pets. If you must travel or be
out in the elements, prepare for extreme cold by dressing in layers,
covering as much exposed areas of skin as possible and pack winter safety
kits in your vehicles. In some areas, being outdoors could lead to
frostbite in minutes. Ensure outdoor animals and livestock have sufficient
shelter.

In contrast to the frigid conditions in the East, the western U.S. will
remain milder than normal.  An Alberta clipper forming along the arctic
front will deliver a period of snow across the northern Plains into the
Midwest during the next couple of days, with areas of rain/freezing rain
over parts of the Northern High Plains on Christmas.  Meanwhile, warmer
and increasingly moist air streaming inland across the Pacific Northwest
will overrun cold air trapped in valleys which could yield mixed
precipitation or significant icing.  Freezing rain potential will extend
to northern Idaho and western Montana as well. 

By Christmas night into Monday, the next low pressure system coming from
the Pacific will deliver the next surge of moisture toward the Pacific
Northwest and then into northern California.

Kong/Campbell


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