Day 1-5 (Today (8/19) through Monday (8/23))
The general themes remain the same for this period. The best heat looks to be in the northern Plains and most of the central US looks to be above normal. Meanwhile the two areas favored to be below normal this period are the Pacific Northwest and New England. We could see highs 100+ in parts of Montana, Wyoming, and the western Dakotas on Saturday and Sunday. Temperatures of 100+ will continue over much of central and eastern Texas and southern Oklahoma through this period. It could even turn hottest with 105+ heat possible in east-central Texas, including Dallas by Monday.
Persistent rain chances will continue over the southeast with much of the rest of the country not seeing too much in the way of abnormal precipitation.
Day 6-10 (Tuesday (8/24) to Saturday (8/28))
Some of the central US heat looks to come east during the period, but overall the immediate east coast may remain near normal as persistent on-shore flow from an off-shore trough/storm complex prevents any big heat from streaming in. The best heat may be in the southwest US, with California heating up along with Las Vegas. The ECMWF model keeps cooler weather over Colorado and New Mexico and in general keeps the plains near or slightly below normal.
A nice cool shot from a strong late season Canadian high will drop into the Plains early next week and spread into the Lakes and eastern US. A 2nd cool shot may drop into the plains by late next week and the weekend.
The southeast US looks to remain the wettest spot across the country.
Day 11-15 (Sunday (8/29) to Thursday (9/2))
It looks like the jet stream may become more active across the northern US as we head into this period. The models are advertising a trough in the northwest US, with a fast jet across the northern Rockies and northern Plains into the Lakes. At the same time an upper rideg may amplify across the southern plains and extend west into the 4 Corners region, and possibly east into the interior southeast. This could create a pattern with some impressive late season heat across the southern US, and perhaps a very storm and severe pattern across the northern plains, Lakes, and northeast US. In general though most of the country will likely be above normal.
Frequent cold frontal passages in the lower mid-Atlantic and upper southeast, may keep the best heat from the lower Mississippi River Valley to the southern plains.