...Additional concerns for flash flooding and severe weather exist into
the weekend across the Northern High Plains...
...Shower and thunderstorm activity will be on the increase over the
Desert Southwest and Central Great Basin...
...Heat will continue across the Southern/Central Plains while much of the Eastern U.S. is in store for a pleasantly cool weekend...
A slow-moving upper low continues to cross the Pacific Northwest and through the weekend will be gradually weakening and shifting east toward the Northern Plains. This will focus unsettled weather across the region with numerous showers and thunderstorms initially focused over the Pacific Northwest and the Northern Rockies, and then advancing east out across the Northern Plains.
Localized threats of severe weather are expected, and sufficiently heavy rainfall is possible that there could be some areas of flash flooding given the relatively slow movement of the system.
In the wake of the system across the Northwest, there will be somewhat cooler temperatures.
Farther southwest back into the Central Great Basin and down into
especially the Desert Southwest, there will be a renewed surge of
monsoonal moisture, and this will support an increase in afternoon and evening shower and thunderstorm activity. Much of the activity will tend to be focused over the higher terrain, but the activity should tend to become more widespread by Sunday and Monday, and it is expected that there will be sufficient transport of moisture for locally heavy rainfall that may result in flash flooding.
The best threat for flash flooding is expected to be areas in and around the Mogollon Rim of Arizona.
Meanwhile, the heat will continue underneath an expansive upper ridge parked over the Central U.S. this weekend. Daytime temperatures across portions of the Central and Southern Plains will climb to near or just over the triple digit mark, with a continuation of very dry conditions.
High pressure initially focused along the East Coast will be move offshore and weaken over the next couple of days, only to give way to the arrival of a new cold front from Canada that will drop down across the Midwest and Great Lakes region through Sunday.
This front will bring a new shot of very cool and dry air which will infiltrate the Ohio Valley, Mid-Atlantic and Northeast late Sunday into Monday.
Overall, rather dry weather is expected to persist across the northeastern third of the nation through the weekend, but that cold front will focus scattered showers and thunderstorms, which will be mostly likely across the Great Lakes region and into New England as the front drops southeast.
Across the Gulf Coast states, generally dry and very warm temperatures are expected, although there will be perhaps some scattered showers and thunderstorms over the immediate Gulf Coast and southern portions of Florida.
Farther west, some increasing easterly flow in off the Gulf of Mexico associated with a weak trough of low pressure may focus a bit more
coverage of showers and thunderstorms for areas of southern Texas, and especially down near the lower Rio Grande Valley. Otherwise, it should be dry.