A front extending from the Upper Great Lakes southward to the Southern Plains moves eastward to the East Coast by Thursday evening.
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Moisture pooling along the boundary will produce showers and severe thunderstorms over parts of the Lower Mississippi and Tennessee Valleys.
Therefore, the SPC has issued a Slight Risk of severe thunderstorms over parts of the Lower Mississippi and Tennessee Valleys through Thursday morning.
The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes.
On Wednesday, the system will also produce showers and thunderstorms over parts of the Great Lakes into the Ohio Valley.
In addition, 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 Central Gulf Coast to the Southeast through Thursday morning.
The associated heavy rain will create localized areas of flash flooding, affecting areas that experience rapid runoff with heavy rain.
Additionally, in the wake of the system, gusty wind and low humidity will produce conditions favorable for fire weather concerns.
Therefore, the SPC has issued a Critical Risk of fire weather over parts of the Northern Plains on Wednesday and over parts of the Central Plains on Thursday.
Furthermore, on Thursday, cold air flowing southward from Central Canada will produce favorable conditions for light snow to develop over parts of the Upper Mississippi Valley, starting overnight Wednesday to Friday.
The threat of severe thunderstorms reduces slightly as the front moves eastward, producing showers and strong to severe thunderstorms over parts of the Northeast and northern Mid-Atlantic on Thursday.
Therefore, the SPC has issued a Marginal Risk of severe thunderstorms over parts of the Northeast and northern Mid-Atlantic from Thursday into Friday morning.
The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, a few tornadoes, and a minimal threat for hail.
However, the threat of excessive rainfall increases over the Northeast on Thursday as the boundary produces showers and thunderstorms with heavy rain.
Therefore, the WPC has issued a Slight Risk of excessive rainfall with these thunderstorms over parts of the Northeast from Thursday into Friday morning.
The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable.
Meanwhile, 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.
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.
The threat for excessive rainfall ends on Thursday over Southern California. ■
Modified arctic air combined with a moisture-laden area of low pressure along the Gulf Coast will continue to allow for a broad area of winter weather impacts from the Lower Mississippi Valley to the Southeast today into early Saturday morning.