An active Tuesday is expected for the Southern Plains with the threat for both severe thunderstorms and heavy rainfall/scattered flash flooding.
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An upper-level shortwave originating over the lee of the Rockies will favorably interact with a warm front and very moist Gulf return flow, leading to robust thunderstorm development Tuesday afternoon.
The Storm Prediction Center has outlined a Slight Risk of Severe Weather (level 2/5) for northwest Texas and Oklahoma where some gusty, damaging winds and large hail will be possible.
In addition, very heavy downpours as well as the expectation storms will begin to congeal/grow upscale into the evening will also lead to the risk for some scattered instances of flash flooding, with a Slight Risk of Excessive Rainfall (level 2/4) in effect.
Storm intensity and coverage will likely be lower on Wednesday as the upper-level wave departs to the east, but some isolated severe weather and locally heavy rain will remain possible.
Late Summer heat is forecast to persist more broadly across the central U.S.
through mid-week as high temperatures reach 10-20 degrees above average.
Highs in the mid-80s to low 90s are forecast for the Central/Northern Plains and Middle Mississippi Valley with upper 80s to mid-90s for the Southern Plains and Lower Mississippi Valley.
Cooler temperatures are forecast for portions of the Northern Plains Wednesday as a cold front passes through and brings increased shower and thunderstorm chances.
Meanwhile, some rain will be possible for the Pacific Northwest Tuesday as a storm system approaches from the Pacific.
Shower and thunderstorm chances will begin to increase more broadly across the northern tier of the West Wednesday as a deep upper-level low drops south from Canada and a quasi-stationary frontal boundary lingers in the region.
Pooling moisture along the boundary and enhanced lift with the approach of the upper-low may lead to some heavy downpours and the risk for isolated flash flooding, particularly for portions of the Northern Great Basin/Rockies.
The upper-low will also bring some much cooler, chilly Fall-like temperatures, with mostly 60s forecast for the Pacific Northwest/Northern Great Basin/Northern Rockies.
Some locations will struggle to even reach 60.
Highs will remain more seasonable to the south ahead of the front/upper-low with 60s and 70s for coastal California, 80s for the central California Valleys east into the Great Basin, and 90s for the Desert Southwest.
Much cooler temperatures will spread into the area by Thursday just beyond the current forecast period.
Elsewhere, showers will linger for northern parts of New England through the day Tuesday as a low pressure system departs to the northeast.
A sweeping cold front that passed through eastern portions of the country the last couple days will leave mostly dry and seasonable conditions for late Summer/early Fall.
Forecast highs Tuesday will be in the 60s and 70s from the Great Lakes/Ohio Valley east into New England and the Mid-Atlantic with low to mid-80s for the Southeast.
Temperatures will warm up a bit on Wednesday with more upper 70s and some low 80s expected for the Great Lakes/Ohio Valley into the Mid-Atlantic.
Daily rounds of showers and thunderstorms will continue for Central and South Florida where the aforementioned frontal boundary will remain draped across the Peninsula.
Some locally heavy downpours are expected and isolated flash flooding may be possible, mainly in urban areas and areas with poor drainage. ■