Conditions will remain hot and humid along the East Coast heading into the weekend as ample moisture remains in place across the region.
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A frontal system slowly pushing in from the west as well as a typical buoyant summertime airmass will lead to the risk of continued thunderstorms through this evening.
Some storms could contain locally intense rainfall rates for portions of interior New England and the Northeast southward into the Mid-Atlantic, with a Slight Risk of Excessive Rainfall (level 2/4) in place through tonight.
After more widely scattered and isolated thunderstorm chances on Saturday, the next round of heavy rainfall is likely to enter the northern Mid-Atlantic and Northeast on Sunday associated with the next approaching frontal system.
A few inches of rainfall are likely, with locally heavier amounts possible within heavier downpours, particularly between eastern Pennsylvania/New Jersey to Upstate New York/Vermont.
A Slight Risk for Excessive Rainfall remains in effect for this region on Sunday.
A pair of meandering frontal systems under energetic flow aloft over portions of the Central/Southern Plains will help to trigger additional rounds of organized convection into this weekend.
With ample surface moisture pooling along the boundaries, a Slight Risk of Excessive Rainfall is in effect from southeastern Colorado through southern Kansas/northern Oklahoma and into southwestern Missouri and northwestern Arkansas through tonight, with another Slight Risk extending eastward into the Lower Mississippi and Tennessee Valleys on Saturday.
Convective systems developing in the late afternoon/early evening and continuing overnight will have the potential to produce additional rounds of heavy rainfall over already saturated soils from recent episodes, with a risk for flash flooding.
In addition, flow aloft will be strong enough to lead to sufficient deep-layer shear for organized thunderstorms, with the Storm Prediction Center issuing Slight Risks for severe weather (level 2/5) generally co-located with the flash flood risk.
A small Enhanced Risk (level 3/5) for severe weather has been issued for the Texas and Oklahoma Panhandles, where the risk for damaging winds is greatest.
Large hail and damaging winds will be the main threats overall.
Additional rain chances are also expected further north into the Northern Plains and Upper Midwest ahead of another frontal system pushing south from Canada this evening.
Temperatures will be seasonably hot south of the fronts over the Southern Plains and Lower Mississippi Valley, with upper 80s to mid-90s forecast.
In contrast, highs will be well below average by as much as 10-15 degrees for portions of the Central/Northern Plains and Midwest.
Temperatures will generally be in the 70s, with a few cooler spots in the upper 60s and a few warmer locations into the low 80s.
Temperatures will generally be Summer-time hot and above average for the interior Northwest and Southwest as areas of upper-level ridging aloft remain in place heading into the weekend.
Heat-related warnings and advisories are in effect for portions of southern Arizona/New Mexico and West Texas as highs rise into the 100s, with low 110s for portions of Arizona.
In addition, Red Flag Warnings as well as a Critical Risk of Fire Weather from the Storm Prediction Center are in place for the Four Corners region as steady winds and very dry antecedent conditions combine with the hot temperatures to enhance the threat for wildfires.
While advisories are not currently in place, highs generally in the mid-90s for interior portions of the Northwest will be running 10-15 degrees above average.
Conditions will be closer to average for the urban I-5 corridor, with 80s forecast.
A pair of upper-level lows/waves just off the West Coast will keep things a bit cooler along the coast from the Pacific Northwest south through California with 60s forecast, and mid-80s to low 90s for the interior valleys.
Additionally, hot and very humid conditions will allow for heat indices to rise between 105-110 across parts of the Florida Peninsula this evening, including Miami and Jacksonville. ■