Monday, 11:45 A.M.
One cold worked its way across the Great Lakes and New England over the weekend, only to stall across the Ohio Valley and mid-Atlantic states as it ran out of gas. That has left the humidity high from Delaware and New Jersey westward across Pennsylvania through the Ohio Valley parts of the Midwest where a second cold front is moving southeastward from the Dakotas. This front looks as if it should make better progress across the Ohio Valley into the mid-Atlantic in the next 48 hours, though eventually it, too, will run out of steam. You can see where the effective front is likely to be later tonight by looking at the 850 mb forecast of heights and temperatures:
You'll note that well out ahead of the front there is an upper-level feature moving into the central Appalachians this afternoon and early tonight, and there's a pretty sizable area of rain and embedded thunderstorms moving through the Ohio Valley at this hour ahead of that disturbance. The rain and thunderstorms will move into and through Pennsylvania later this afternoon and tonight, eventually overtaking parts of upstate New York later tonight and tomorrow morning. From there the wet weather will move into New England, where there can be a good, heavy soaking for a time tomorrow before tapering off tomorrow night.
With this front making more progress through the Ohio Valley and mid-Atlantic states tomorrow afternoon and tomorrow night, Wednesday promises to be less humid throughout the Ohio Valley, and even down into Maryland and Delaware, though much farther south this front will not offer much relief from the humidity.
It will not, however, be the last front for a while. Indeed, still another front is on tap for the northern Plains Thursday:
This front will slow down some as it moves across the Lakes and Ohio Valley Friday and Friday night into Saturday. An upper-level low appears likely to form over Ontario by Thursday, a feature that will move slowly toward the east Friday into the weekend. Because it will form so far west to start with, it will allow the flow east of the Appalachians to back into the west-southwest for a time, preventing the front from just charging over the mountains to the coast and offshore. In fact, there are some computer models, such as the European, that don't effectively bring this front off the East Coast until late in the weekend!
Anyway you slice it, though, the main theme is this: the heat of last week along with the tropical humidity is very unlikely to be repeated the rest of the month, offering some cooling relief from the northern Plains and Midwest to the mid-Atlantic.
There will be plenty of heat and humidity from the southern Plains to the East Coast this week while much cooler air prevails for a time over the Northwest to the northern Plains.
Severe thunderstorms raked across the Midwest and Ohio Valley in the past 24 hours, with more on the way this afternoon. The pattern will repeat itself over the next week.
The strong upper-level ridge over the southern Plains will promote intense heat there, while it forces disturbances through the Midwest toward the Ohio Valley with severe thunderstorms to follow.
A strengthening upper-level ridge of high pressure over Texas and Oklahoma will dry out the Plains, but it will remain unsettled from the Dakotas to the central Appalachians, as the Northwest trends cooler.
A wet week lies ahead from the southern Plains to the Ohio Valley as a wavy front becomes the focal point for showers and thunderstorms containing flooding downpours.