Overall, the general flow pattern features troughing across the West and Southeast and ridging over the Northeast.
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The Western trough, with cooler temperatures aloft, will trigger showers and thunderstorms across the Great Basin into the Northern Rockies of Montana each day once daytime heating increases the available instability; strong to severe thunderstorms will be most active from late afternoon into the evening hours from southeast Montana through the western Panhandle of Texas through the Memorial Day weekend.
A Moderate Risk for scattered to numerous instances of flash flooding is expected this evening and tonight across portions of the Permian Basin/Caprock of Texas; 4-10" of rain has fallen in that area over the past couple of days.
The severe weather risk will be more limited in coverage and intensity into Monday through the length the High Plains, with the best potential across the northern High Plains.
Some of these thunderstorms will be slow-moving and have the potential for very high rainfall rates.
The severe weather and heavy rain potentials are expected to shift only slightly eastward but again cover the length of the High Plains Sunday into Monday morning.
Meanwhile, a convective low pressure system has strengthened moving over the Atlantic waters off the coast of the southeastern U.S.
Bands of heavy rain are expected to push onshore tonight with strengthening winds prior to the arrival of the low center on Sunday morning.
Coastal communities across the Southeast can expect strong and gusty winds, high surfs, in addition to life threatening rip currents for much of the weekend.
Boating conditions will be treacherous with a Storm Warning issued by the Ocean Prediction Center/NWS Forecast Office in Charleston for the offshore waters of the Carolinas.
Meanwhile, squally showers and thunderstorms are expected to spread inland with high rainfall potential.
A Moderate Risk of Excessive Rainfall will remain in effect for parts of the NC/SC coastal plain tonight; scattered to numerous instances of flash flooding are expected.
On Sunday, once moving inland, the low pressure system is forecast to gradually weaken.
Heavy rainbands on the outer periphery of the storm are forecast to push northward across Virginia on Sunday, with the occurrences of flash flooding expected to be more isolated to widely scattered.
Slow improvement in the weather is anticipated into Monday morning but cloudy and rainy conditions are expected to cover the southern to central Mid-Atlantic States on Memorial Day.
Elsewhere, across the Mississippi Valley, Great Lakes, Northeast and Southwest should have a very pleasant weekend.
Temperatures will be average for much of the southern portion of the central U.S.; though the northern tier, particularly the Plains and Upper Great Lakes will see above normal but not oppressive temperatures in the 70s and 80s. ■