Weather across America

(NATIONAL) A Slight Risk of excessive rainfall over parts of the Mid-Atlantic, an Enhanced Risk of severe thunderstorms over parts of the Ohio/Tennessee/Lower Mississippi Valleys, Excessive Heat Watch/Warnings and Heat Advisories over the South, and Air Quality alerts over parts of the Upper Mississippi Valley.  

A front extending from parts of the Upper Midwest to the Southern Plains will move eastward to the Mid-Atlantic Coast, Southeast westward to the Southern High Plains by Tuesday. The boundary will produce showers and severe thunderstorms over the Ohio/Tennessee/Lower Mississippi Valleys. 

Therefore, the SPC has issued an Enhanced Risk of severe thunderstorms over parts of the Enhanced through Monday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. Additionally, there is a threat of EF2 to EF5 tornados over the Ohio Valley and severe thunderstorm wind gusts of 65 knots or greater over parts of the Ohio Valley and Lower Mississippi Valley/Southern Plains through Monday morning. 

Furthermore, the showers and thunderstorms will produce moderate to heavy rain over the Great Lakes and Ohio/Tennessee/Lower Mississippi Valleys on Sunday. Therefore, through Monday morning, the WPC has issued a Marginal Risk of excessive rainfall over parts of the Great Lakes, Ohio Valley, Tennessee Valley, and Lower Mississippi Valley.

The associated heavy rain will create localized areas of flash flooding, affecting areas that experience rapid runoff with heavy rain.  Further, the threat of severe thunderstorms moves eastward and continues over parts of Virginia and North Carolina on Monday. Therefore, the SPC has issued an Enhanced Risk of severe thunderstorms over parts of the Mid-Atlantic from Monday through Tuesday morning. 

The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. Additionally, there is a threat of two-inch or greater hail over parts of Eastern Virginia and Central North Carolina from Monday through Tuesday morning.  

Additionally, the threat of excessive rainfall increases on Monday over parts of Pennsylvania, Maryland, Delaware, Virginia, and North Carolina on Monday. Therefore, the WPC has issued a Slight Risk of excessive rainfall over parts of the Mid-Atlantic from Monday into Tuesday 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 impulses and a developing upper-level trough will trigger scattered showers and thunderstorms over parts of the Great Basin and Pacific Northwest on Saturday, continuing into Monday.   

Upper-level impulses and a developing upper-level trough will also trigger scattered showers and thunderstorms over parts of the Great Basin, Pacific Northwest, Northern California, and the Northern Rockies on Sunday, continuing into Tuesday. The showers and thunderstorms will also move into the Northern/Central Plains Monday into Tuesday.   

An upper-level high over the south-central portion of the country, along with high temperatures and temperatures not cooling off much overnight, have contributed to Excessive Heat Watches/Warnings and Heat Advisories over most of Texas, southern New Mexico/Arizona, southeastern Oklahoma, Louisiana, Arkansas, Mississippi, and western Tennessee.  

Lastly, wildfire smoke in Canada will reduce air quality over parts of the Upper Mississippi Valley prompting Air Quality Warnings over the area.