This will be the most memorable week of extreme winter weather centered around Christmas in a generation.
And it WON'T all be pretty. I'm making this claim based on the cumulative impact of cold, wind, and snow during the busy holiday travel days leading up to Christmas (Thu-Sat).
A powerful winter storm - and likely a blizzard in some areas - will mark the arrival of an arctic blast that will make holiday travel nearly impossible in some areas, and any last-minute shopping miserable for most.
This is my early call on accumulations for the primary storm system moving through the Plains and Midwest Thursday and Friday. The map does not factor in any blowing or drifting of the snow that may occur through the weekend.
If you're wondering about a white Christmas, I will post an update to the probabilities posted in this story on Tuesday. Spoiler alert: Chances are much higher across Missouri and Illinois (>80%), but a bit lower from Oklahoma to Tennessee (<30%).
The bigger story during the upcoming holiday travel period is likely to be the extremely cold air mass that follows. Subfreezing temperatures will dive as far south as the Texas Gulf Coast and the I-4 corridor across Florida.
Following the initial surge of arctic air, the combination of snow cover and a weaker front or two will keep temperatures below normal for several days following the Christmas holiday for the majority of the eastern two-thirds of the nation.
How the Storm Unfolds
An arctic front will be plunging south through western Canada Wednesday, then across the northern and central Plains Thursday. An upper-level disturbance will ride this polar jet stream south and spawn a low-pressure system over the Mid-South.
A tightening pressure gradient, plummeting temperatures, and sufficient moisture will lead to expansive wintry precipitation, primarily in the form of snow and blowing snow from the Southern Plains to the Ohio Valley as the low moves northeast. A swath of heavy snow and near-blizzard conditions will be possible northwest of the storm track, which at this time is most likely to occur from the eastern Ozarks to the western Great Lakes Friday and Saturday.
Frigid temperatures and wind chills will catch up to the snow quickly. This will be an abnormal snow event for many cities at a more southern latitude where only marginally cold enough temperatures usually accompany the flakes. For example, the majority of snowfall in St. Louis will occur at temperatures lower than 20º. Subzero temperatures and wind chills will follow the precipitation for many days, leading to one of the coldest Christmas holidays in many years.