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.
A series of cold fronts will impact the weather now through the weekend, largely across the northern half of the country.
Just as I head for British Columbia to do an Ironman, the recent heat is leaving and heading onto the Plains, while it cools off in the Northwest for a spell.
A disturbance in Wyoming will be the focal point of unsettled weather into next week from the northern Plains to the Northeast, keeping heat at bay.
Record rains have inundated parts of the mid-Atlantic over the past 24 hours. A disturbance coming from Arizona will produce showers and thunderstorms with locally heavy rain as it heads for the Midwest this weekend.
Closed lows aloft will bring wet weather to the Northeast and the Northwest into the midweek period, with cool air spreading from the Midwest to the East Coast the rest of this week.
Heat has been lacking from the Midwest to the mid-Atlantic much of the summer, and that pattern will continue though the week and weekend into early next week.