Flash flooding will be possible over portions of the Southwest...
Temperatures will be on the rise across the Upper Midwest...
Conditions should stay pleasantly cool and dry across the Northeast and Mid-Atlantic states...
Widespread convection will continue to fire up across the Western U.S. this weekend. Moisture getting pulled northward in-between a trough digging into the West and an upper ridge building in over the Central U.S. will fuel numerous showers and thunderstorms over the Southwest and along the Southern to Central Rockies.
Flash flooding will be a concern over a large portion of Arizona and into southern California...where plenty of moisture moving in from Tropical Storm Ivo could lead to tropical downpours within developing thunderstorms.
Showers and thunderstorms are also expected farther north...where energy rotating around the upper trough digging into the West should help trigger scattered convection across northern California and up into the Pacific Northwest.
A frontal boundary stretched through the north central U.S. will begin
moving eastward as a warm front on Saturday. Enough moisture in place ahead of the boundary should allow for some showers and thunderstorms to break out across the Upper Midwest.
By Sunday...precipitation should be confined to the Upper Great Lakes as the front lifts into Canada and strong upper ridging begins to expand over the central U.S..
The building ridge will bring a big rise in temperatures across the Dakotas and Upper Midwest...and heat advisories have already been posted across the region.
Meanwhile...a strong surface high setting up over the Eastern U.S. will
keep conditions pleasantly cool and dry across the Northeast and Northern Mid-Atlantic states.
Farther south...a frontal boundary slowly sinking southward through the Gulf Coast States will be the focus for showers and thunderstorms for the remainder of the weekend.