A ribbon of hot, humid air has been fueling some nasty thunderstorms in recent days, and that continues today. Look at just the severe weather reports for the past 24 hours, ending at 8 a.m. EDT:
One disturbance pulled some of the heat and humidity toward the mid-Atlantic and New England, triggering potent thunderstorms with a lot of wind damage, mainly across upstate New York. Much farther west, some thunderstorms spawned tornadoes in Nebraska and northwestern Iowa. Part of that was tied to the upper-level low over Idaho, while the rest in the Midwest was more triggered by a relatively weak upper-level disturbance moving across the region.
This afternoon that same disturbance will spark nasty thunderstorms with damaging winds, hail, flooding downpours and even an isolated tornado, from southeastern Wisconsin and northern Illinois into southern Michigan and across the Ohio Valley.
Most of these thunderstorms will run along the boundary that separates the truly hot and humid air from an air mass that's not as hot and clearly not as humid. The thunderstorms coming out of the Midwest and across the Great Lakes and Ohio Valley will essentially be tied to a cold front that will easily pass off the southern New England coast tomorrow morning but run into more and more resistance trying to get through the mid-Atlantic. In the latter area, the unsettled weather will linger deep into tomorrow, and, in some cases, even tomorrow night.
The front will finally stall by Friday morning from the lower Chesapeake Bay back to near Chicago, and it will remain the focal point for showers and thunderstorms. South and west of that boundary, the air mass will remain very toasty and humid with dew point temperatures close to, if not a little above, 70. And that boundary isn't apt to move an awful lot going into the weekend. If you examine the upper-level pattern, the anchor point will be the intense upper-level low over Labrador, seen here Saturday evening:
With weak upper-level ridging over the Rockies, the upper-level flow will be oriented east-southeastward toward the mid-Atlantic coast, keeping that boundary largely in place. And as a result, it will mean little ripples or upper-level disturbances moving along this boundary, trying to pull it or push it one direction or another. And this will continue through the weekend.
In the end by early next week, this boundary will be a little farther south, and the air will be rather stable and dry in the Northeast, at least for a time. In contrast, there may not be a dry day in the next week across the Midwest and middle Mississippi Valley into the Ohio Valley! Farther south, it will be seasonably hot and humid with scattered afternoon and evening thunderstorms, but nothing very well organized.
The tropics remain quiet 18 days into the Atlantic season, and there's a very good chance we escape June with no tropical development in the Atlantic Basin.
Slow changes mean more wet weather across parts of the southern tier of states through the weekend, while a faster jet stream will bring more swift changes to the northern tier states.
Odile will bring flooding rains to parts of Arizona and New Mexico over the next three days, but most of the rest of the country will rather quiet weather.
Much of the country from the Plains to the East Coast will have several more days of very cool weather. Meanwhile, Odile is threatening Arizona and New Mexico with flooding rains later this week.
A strong storm in Quebec combined with a very large high near Montana will result in sweeping changes across the Ohio Valley into the mid-Atlantic and Northeast in the next 24 hours.
The latest surge of heat and humidity into the Midwest will spread to the East tomorrow but be trimmed back to the South later this weekend by the passage of a cold front.
Summer's heat and humidity will still have a period of time to sizzle the rest of the week into the start of the weekend, but a fall-like air mass will invade the northern Plains and Midwest this weekend.