Weather across America

(NATIONAL) Oppressive to dangerous heat and humidity continues across the southern Plains, heat increases across the Desert Southwest and interior valleys of California, the threat of heavy rain moves southward into the Southeast and near the central Gulf Coast, and a severe thunderstorm threat is expected to track across the northern tier states.

An upper-level high anchored over the southern Plains will continue to sustain the ongoing heat wave across the region for the next couple of days. Farther east, the effect of high humidity will make the heat more oppressive over the lower Mississippi Valley even though the temperatures there are not expected to climb as high.  

Heat indices are forecast to once again peak above 110 degrees at many places during the afternoon on Monday. Slightly cooler air behind a cold front is forecast to work its way down the central Plains during the next couple of days, bringing in some welcome relief there through Tuesday. However, the interior Desert Southwest and interior valleys of California will see the heat increasing in intensity, especially Monday afternoon, with actually temperatures likely exceeding 115 degrees at the hottest locations in the desert.  

Meanwhile, waves of low pressure forming along a cold front will gradually shift the threat of heavy rain southward into the Southeast for tonight and early Monday. By later on Monday into Tuesday, tropical moisture gathering in the northern Gulf of Mexico will begin to interact with the nearly stationary front where the threat of heavy rain is forecast to increase near the central Gulf Coast by Tuesday.  

In the meantime, upper-level energy and a weak front will track across the northern tier states for the next couple of days. Strong to severe thunderstorms are possible near and ahead of the front. The highest threat of severe storms with locally heavy downpours is expected to be across the northern Plains to the upper Midwest through tonight, shifting east into the Midwest on Monday, and then into parts of the Northeast on Tuesday.  

The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes.  

Farther south, weak monsoonal moisture will trigger diurnal showers and thunderstorms over parts of the Southwest, southern Rockies, and into parts of the Central Rockies for the next couple of days. On Monday into Monday night, some of the moisture is forecast to interact with a front to increase the threat of heavy rain over the High Plains of southern Colorado into northern New Mexico.