We have an interesting next 7 days coming up for the Lower 48. Firstly, an area of disturbed weather that was once Tropical Storm Chantal continues to spread NW through the Bahamas with a lot of tropical moisture bumping up against an unusually far south dipping which is dropping all the way towards the Gulf and Southeast coast of the US. The combo of rich tropical moisture lifting north while the jet dips that far south presents a renewed flood threat to the Carolinas up into Virginia, Maryland, possibly Delaware and New Jersey as well as points west this weekend. Heavy rains are currently impacting eastern Virginia, Maryland, Delaware into southeast Pennsylvania at this time and this situation will continue through the weekend.

Tomorrow will mark day 5 of 100+ in Dallas and I believe Oklahoma City too but that streak comes to an abrupt end Saturday into Sunday as the low within the trough retrogrades southwest from Ohio down to Texas and so while it should hit 100 tomorrow, a front drops through Sunday and highs will only reach 90 with rain chances greatly increased. The following 4 or 5 days looks very pleasant for the time of year but what’s Texas’ gain, it’s the Midwest and Northeast’s loss.

Here’s the GFS precip thro0ugh 48 hours (Sunday) and it sure looks like a messy weekend for the Southeast and up the coast.

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What will happen from now through Sunday is that low over the Ohio Valley drops southwest and as it does so, it forces the heat around the north side of the low. So while it brings a significant cooldown to toasty Texas and oven-like Oklahoma tomorrow again, it will bring rain and much cooler air down Sunday while it heats up over the Midwest including major cities such as St Louis, Chicago, Indianapolis and Pittsburgh.

Here’s the 500mb vort max chart which shows the low and trough over the Ohio Valley with the ridge and heat to the west surging north while the tropical hose runs up it’s east side.

Now check out this chart for late in the day Sunday.

Notice how far southwest that low goes while the heat drives right across the Ohio Valley and builds over the Northeast. I expect a steady temperature rise for the Big Cities Sunday through next Wednesday or Thursday with a string of 90s. In fact by mid next week, it wouldn’t surprise me if it gets to 96 in New York City while Philadelphia pushes 97 but bare in mind there’s a LOT of moisture in the ground and this could not only temper the heat but significantly lift dew points.

By next Tuesday, a strong ridge sits parked over the Ohio Valley and Northeast but the position of the upper trough over West Texas means plentiful rains for the Southwest and Rockies.

Here’s the precip chart for Tuesday.

As for the latest CFSv2 temperatures, notice the heat lifting from Texas up into the Northeast week 1 as the low dives southwest, replacing the source with cool and wetter conditions but that heat shrinks and backs west back to the Plains week 2. Also notice the tongue of cool surging north from Mexico up into New Mexico, eastern Arizona and the Rockies, thanks to tropical moisture pushing up from the Gulf

By week 3 and 4, the building pool of cool over Canada gets replaced by warm air and all the cool appears to largely dominate the US into the first week of August. Just the immediate West Coast and Southern and Central Plains remains warm.

Here’s the August foreceast. Moral is, if you like the heat, enjoy it while it lasts because it’s looking like August could well be a pretty cool month from Montana to North Florida.

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