Tuesday, 11:00 A.M.
The last of the big rains associated with the slow-moving cold front have cleared Cape Cod and Cape Hatteras. Colder and much drier air has finally won the fight along the Eastern Seaboard, and aside from a few spotty showers in parts of southeastern Florida the rest of the day, rain is now absent from the country. There area a few places where there is some snow, but none of it is heavy, though what there is can be enough to cause travel issues, especially from northern and western Pennsylvania into parts of upstate New York, as well as parts of the Midwest this afternoon and early tonight.
Take that away, and there's not much going on around the country, weather-wise. It's as if the weather is taking a holiday, too. Oh, there will be some places with dicey weather this afternoon and evening, and we'll have to track this upper-level trough spreading light snow across the Midwest this afternoon and tonight as well. It's a system that will bring some Christmas Day snows across the Lakes, albeit light, and could have some last-minute surprises in store for parts of New England.
About the only place that will have any kind of rain through Friday will be Florida as moisture is brought off the Gulf stream underneath the surface high to the north. And even that won't be a lot, but it can lead to spotty showers through tomorrow, especially along the East Coast of Florida.
To break this down feature by feature, let's look at the intense but moisture-starved, upper-level trough swinging through the Northeast today. It is generating some snows across upstate New York and Pennsylvania now as it swings through. Here's the 12z Dec. 24 NAM 500mb forecast for this evening:
The snow isn't heavy, but it represents the leading edge of some bona fide arctic air, as temperatures will go from near or even above freezing ahead of this trough/cold front down through the 20s, and into the teens, as is the case at this hour over northwestern Pennsylvania and Ohio. It's even colder farther west! While the air will modify to some extent as it moves over the barren ground east of the Appalachians, it's still going to be cold on Christmas in the East.
The second feature is really going to be split into two pieces. The first as you can see from the image above will spread the light snow across the Midwest this afternoon and tonight, and then into the Lakes tomorrow, but the second piece will come into play Christmas night:
This will induce more fitful bursts of snow across northern and western Pennsylvania and upstate New York late tomorrow night and Thursday morning, but, much like today, the snow amounts won't be excessive. There could be some last-minute shenanigans with it as it reaches the New England coast late Thursday and it starts working with a much more moist environment. It wouldn't shock me to see a few quick inches of snow fall out of this late Thursday in eastern Massachusetts, and even more in parts of Maine as in inverted trough sets up for a time. But it is a progressive feature, so the "favorable" snow conditions won't last for long before moving on.
By the time we get to Friday, cold high pressure will set up camp in the East, while a large high sprawls out over the Intermountain West:
That will mean a mild finish to the week from the Plains to the West Coast, all things being equal, and a cold but mainly dry end to it from the Lakes to the Northeast and mid-Atlantic states. It will be wet in Florida as a wave of low pressure tries to form off the Southeast coast along the old frontal boundary.
The next big ticket item will a storm that will pass through southern Canada and drags a strong cold front into the Plains this weekend, then off the East Coast late Sunday and Sunday night. Ahead of the front the cold will ease from the Mississippi Valley to the Eastern Seaboard, then behind the front another blast of arctic air will drill across the northern Plains and Midwest to the East Coast. The next larger storm potential may not be until the middle of next week around the start of the new year.
A turn to much colder air over the Northeast and mid-Atlantic states will set the stage for a rain and snow storm later this weekend before it turns much warmer later next week.
It's warm now, but will turn much colder this weekend, with a storm threat later Saturday into Sunday. Warmth will return by the second half of next week.
Though it is cold now east of the Mississippi, with a couple of opportunities for snow into the weekend, a blast of warmth is due for much of the country east of the Rockies next week.
Warm air will once again surge eastward from the Plains to the East Coast this weekend and early next week. A strong storm next Tuesday and Wednesday will then be followed by colder air later next week.
A storm in Southeast Texas will generate severe thunderstorms this afternoon and tonight, and some wet snow on its western flank as it heads into the Ohio Valley tomorrow.
A major spring storm will move from Texas tonight to the eastern Great Lakes Wednesday night, producing heavy rain and severe thunderstorms, with a swath of heavy, wet snow on its western flank.