Monday, 11:30 A.M.
The message I have this week is to be thankful if you are not a real big fan of cold weather. This is your week. If, on the other hand, you enjoy arctic air, then you, too, can be just as thankful, as it is coming sooner rather than later.
The week is starting out on a relative high note in much of the country. We're still dealing with a pesky and slow-moving storm off the Carolina coast, one that really won't get kicked out of the way until Friday. On the other side of the continent, there's a similar upper-level low rolling around the North Pacific, one that has been sending pieces of energy at the Northwest this weekend. It will continue to do so over the next couple of days, though the action may shift north on Thanksgiving Day.
In between, there isn't any arctic air, and there's every reason to believe some record highs will be set over the next three or four days from the eastern Rockies to the Ohio and Tennessee valleys. Even with the passage of one cold front Wednesday and Thursday across the Plains toward the Midwest, with a nice little piece of cold air moving in for a day or two behind it, temperatures will still run well above normal from tomorrow through next Monday. Take a look at the GFS ensemble 7-day means:
The core of the initial warm period ahead of Thanksgiving will be in the central and northern Plains. Look at the one-day anomaly forecast for Wednesday:
The front will progress to off the New England and mid-Atlantic coast Friday night, shoving the pesky offshore storm out of the picture. There will be a nice surge of mild air ahead of this front into the Great Lakes and Ohio Valley on Thanksgiving Day with a good deal of sunshine, and a similar surge of warmth into the East on Friday ahead of the front, though the departures from normal will be smaller east of the Appalachians.
As we have seen this past week, the place that will see the bigger impact of the chill will be the Southeast. Why? That's where high pressure will move into, and even though the coldest air will be aimed at the Northeast, the fact there will be clear skies with little wind at night across the South into the Southeast will lead to frosty night time lows this weekend. Furthermore, with the low sun angles, the typical mixing by day will be limited, keeping temperatures from rebounding too quickly over the weekend.
By the same token, though, the cold is in and out across the Rockies and Plains. By Saturday, afternoon temperatures will rebound into the 50s over eastern Montana and the Black Hills of South Dakota, and some 60s farther south.
If you look at the images above, though, there should be something else that stands out - the various shades of "cold" depicted farther north and northwest into western Canada and Alaska. It appears more and more likely that a somewhat bigger piece of that cold, arctic air is poised to be let loose on the Rockies and Plains next week in the wake of a storm and its attendant cold front. The models do have some differing ideas on what that looks like, as you might suspect that far in advance, but the overarching theme is for a storm to cut for the lakes and drag a cold front out of the Rockies, across the Plains and, eventually later in the week, into and through the East.
Given the tendency of the atmosphere to become fairly amplified, it would not surprise me at all if this feature ended up a little stronger than is being currently suggested. It may not be one of these cold air masses that comes in and sticks around for a while, but it should represent a dramatic change for much of the country from the eastern Rockies to the East Coast as we make the transition from November into December.
Blocking over the Atlantic and in Europe is buckling the jet stream over the central and eastern U.S. to extend the cool and wet weather the rest of the week and into the weekend.
More excessive wetness is in store from the mid-Mississippi Valley to the mid-Atlantic states, while the brutal heat continues in the West and especially the Northwest this week.
A cool season storm will bring flooding rains and very cool air to the Ohio Valley and Northeast tomorrow into the weekend, while the Northwest has record-setting heat with sunshine.
As the jet stream undergoes amplification late this week into the weekend, it will lead to extremes of heat in the Northwest and cool and wet weather in the Ohio Valley, mid-Atlantic and parts of New England.
Heat and humidity surging across the Mississippi Valley will spark severe thunderstorms in the next 24 hours. The pattern will remain wet from the northern Plains to the East Coast for a while.