Upper-level energy over Southern California and moisture surging northward along the Southern California Coast will aid in producing showers and thunderstorms with a potential for heavy rain over parts of Southern California.
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Therefore, the WPC has issued a Marginal Risk of excessive rainfall over parts of Southern California through Thursday morning.
The associated heavy rain will create localized areas of flash flooding, affecting areas that experience rapid runoff and burn scars.
Meanwhile, high pressure over the Mid-Atlantic into the Northeast will move off the East Coast by Wednesday.
The high pressure will produce clear skies and calm wind, allowing temperatures to go below or near freezing on Tuesday morning.
As a result, parts of the Northeast have Freeze Warnings and Frost Advisories out until 8-9 AM local time.
Furthermore, a front extending from parts of the Northern Plains to the Northern Intermountain Region on Tuesday will move eastward to the Lower Great Lakes, then southwestward to the Southern Plains/Western Gulf Coast by Thursday.
The boundary will produce rain and rain/wet snow over parts of the Northern Rockies/Northern High Plains on Tuesday morning.
In addition, moisture will move into the Middle Mississippi Valley on Tuesday, moving into the Great Lakes/Ohio Valley by Wednesday.
By Tuesday evening, the front will move into the Upper Mississippi Valley to the Central Plains, producing showers and strong to severe thunderstorms along and ahead of the associated front over parts of the Upper/Middle Mississippi Valley and Central Plains.
Therefore, the SPC has issued a Marginal Risk of severe thunderstorms over parts of the Upper/Middle Mississippi Valley and Central Plains through Wednesday morning.
The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a minimal threat of tornadoes.
As the front moves, the threat of severe thunderstorms moves eastward on Wednesday.
Therefore, the SPC has issued a Marginal Risk of severe thunderstorms over parts of the Ohio Valley, Middle/Lower Mississippi Valley, and Tennessee Valley from Wednesday into Thursday morning.
The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes.
Moreover, in the wake of the front, temperatures will cool off, allowing wet snow to develop over parts of the Upper Mississippi Valley Wednesday night into Thursday.
Elsewhere, a weak front and easterly flow off the Atlantic will allow showers and thunderstorms to develop over parts of the Florida peninsula through Wednesday morning.
Overnight Tuesday, moisture will surge northward from the Gulf of Mexico over the Gulf Coast.
By Wednesday morning, moisture will interact with upper-level energy to produce showers and thunderstorms with a potential for heavy rain over the Gulf Coast into parts of the Southeast.
Therefore, the WPC has issued a Marginal Risk of excessive rainfall over parts of the Gulf Coast into parts of the Southeast Wednesday into Thursday morning.
The associated heavy rain will create localized areas of flash flooding, affecting areas that experience rapid runoff with heavy rain. ■