A potent upper-level trough over the northern Rockies and an associated cold front advancing southeast will set the stage for numerous rounds of showers and thunderstorms across the northern Plains and Upper Mississippi Valley going through tonight into early Saturday.
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An anomalously warm and moist airmass ahead of the approaching front will lead to conditions favorable for thunderstorms to turn severe.
The Storm Prediction Center has maintained an Enhanced Risk (level 3/5) of severe thunderstorms for eastern North Dakota, northeastern South Dakota, and northwestern Minnesota.
Damaging wind gusts, very large hail, and a couple of tornadoes are possible, with the potential for severe thunderstorms extending southward to Nebraska and western Iowa as well.
Along with the severe potential, heavy rain may lead to some flash flooding from eastern North Dakota to northern Minnesota.
A Slight Risk (level 2/4) of excessive rainfall has been issued to highlight this concern.
Meanwhile, monsoonal moisture will remain in place throughout the Southwest and into the southern/central Rockies through this weekend.
This will lead to continuing chances for scattered thunderstorms and at least an isolated threat of flash flooding.
By Saturday, a cold front is still expected to approach and should focus more organized convection from northern New Mexico to southwest Kansas.
These thunderstorms may be slow-moving and will be capable of producing heavy rainfall amounts.
Some of the burn scar locations in the Sangre De Cristo range of south-central Colorado and northern Mew Mexico will be particularly vulnerable to runoff concerns and flash flooding due to this heavy rainfall potential.
A Slight Risk of excessive rainfall has been issued for these regions on both Saturday and Sunday.
Elsewhere, chances for scattered showers and thunderstorms will continue across the eastern Gulf Coast, Southeast, and Florida through this weekend.
Dangerous heat will remain a concern over much of the South through this weekend.
High temperatures underneath a stagnant upper-level ridge will soar into the upper-90s and low 100s from the southern Plains to the eastern Gulf Coast.
Heat Advisories have been issued from central Texas to the western Florida Peninsula as heat indices potentially approach 115 degrees through this evening.
Excessive Heat Warnings are posted for parts of Louisiana, including New Orleans, as well as southern Mississippi and the Big Bend of Florida.
Slightly cooler air will enter parts of the Southeast and Florida on Saturday as easterly winds off of the western Atlantic offer some relief.
However, sweltering heat is forecast to continue across the Southern Plains and Lower Mississippi Valley while potentially threatening a few daily high temperature records.
Farther north, above average temperatures with highs into the upper-90s will reach into the mid-Mississippi Valley on Saturday ahead of the approaching upstream cold front, with low 90s making it into the northern Appalachians on Sunday.
For the Pacific Northwest, summer is finally making an appearance and could bring with it dangerous heat.
Highs are forecast to climb each day through Sunday and reach into the 90s across much of the region, with 100s farther south into the central valley region of California.
Heat Advisories have been issued for western portions of Washington and Oregon for Saturday and Sunday. ■