Friday, 11:30 a.m.
The weather pattern is changing, that much is certain. Fall is eight days from officially beginning, but it will be arriving early in a lot of places east of the Rockies, if it hasn't felt like it already. Some highlights of the week ahead:
1) A weakening cold front will slip through the Northeast Friday night. There won't be a lot of rain with it, with most of it coming through early tonight. There will be almost nothing for southeastern New England and the mid-Atlantic states.
The cooling behind this front that has been quite strong in the eastern Rockies and Plains the past couple of days will be far, far less in New England and especially the mid-Atlantic states. And it will be recovering nicely behind it in the Great Lakes and Midwest later this weekend.
2) Amplification in the pattern next week. Look at the forecasts of the North Atlantic Oscillation (NAO) and Pacific North America (PNA) pattern:
As this develops, the stage is set for a trough coming through Canada to dive into the Midwest to open up next week:
This will bring the coolest air so far this season down into the Plains and through the Mississippi Valley, then into the Ohio and Tennessee valleys into the South and Southeast.
3) The core of cool air centered from the Plains and especially Mississippi Valley to the Appalachians. Look at where the trough axis sets up:
That image for next Thursday evening clearly shows the downstream blocking, as well as the upstream ridging, with the deep trough between them. There will be no place for the cool air to go but into the nation's midsection. Look at the weekly departure forecast off the GFS ensemble seven-day means:
If I were a betting man, I'd say the 90-degree days are done from Des Moines to Chicago to New York, and probably even from St. Louis to Washington, D.C. I'm not a betting man, but by the time, we recover from this, it is likely to be October, and it's really hard to get that hot that late into the season north of the I-70 corridor. Not impossible, but hard. We'll see.
If you want warmth, head west. The Northwest will have plenty of sunshine and warmth in the next week to 10 days or more.
Heavy rain will soak drought-stricken areas of the mid-Atlantic over the next couple of days. Focus will then shift to Matthew and its potential to impact the Eastern Seaboard with more heavy rain later next week.
Summer has ended astronomically, but from a meteorological standpoint, there's plenty more warm weather heading into October from the Plains to the East.
Two strong cold fronts will charge across the country in the next week, eventually taking out the current hot and humid air mass from the Plains to the East Coast.
Over the next three days, hot and humid air will expand across the Mississippi Valley all the way to the East Coast. This will be followed by even more heat and humidity leading into the weekend.
Hermine will head across the Florida Panhandle late tonight, then cut across the coastal Carolinas and become a headache for the mid-Atlantic and southern New England over the Labor Day weekend. It will be followed by a heat wave later next week.
The heat and humidity will be erased from much of the East later this week, but warmth will spread from the Plains eastward over the weekend. The tropics could still play an important role in the weather along the Eastern Seaboard this weekend.