Weather across America

(NATIONAL) Excessive rainfall and severe thunderstorms possible over portions of the Great Plains and Mississippi Valley, heavy to excessive rainfall possible across parts of the Northwest, and an increasing excessive heat threat over parts of California, Nevada and Arizona.

A series of shortwaves will be responsible for excessive rainfall and severe thunderstorms that develop across the Great Plains and Mississippi Valley over the next few days. Showers and isolated thunderstorms will be spread from the High Plains into the Mississippi Valley. Some storms may turn severe.

The Storm Prediction Center issued an enhanced risk (level 3/5) of severe thunderstorms across portions of the Central High Plains through Sunday evening. Very large hail, severe wind gusts greater than 75 mph, and a few tornadoes are expected. Rain rates in some of those storms could be high enough to cause flash flooding which is why there's a slight risk (at least 15%) of excessive rainfall over parts of the Northern and Central Plains and Upper and Middle Mississippi Valley.

Elsewhere, a deep upper low will transport anomalous tropical Pacific moisture into the Northwest. Excessive rainfall is naturally a concern over the favorable terrain of the Cascades, Bitterrroots, Salmon River Mountains as well as the Seattle metro, where Slight Risks (at least 15%) are in effect through Monday.

Monday will be a marginal risk kind of day for excessive rainfall and severe thunderstorms over parts of the Southern and Central Plains and Mississippi Valley. Cloudy and cooler conditions will prevail over the Northwest thanks to the Atmospheric River event set to unfold over the next couple of days. Otherwise, the Great Plains and Northeast are likely to experience above average temperatures this week. Abnormal heat is expected to expand across parts of the West mid-week.