Weather across America

(NATIONAL) A Moderate Risk of excessive rainfall over parts of the Upper Great Lakes and Upper/Middle Mississippi Valley, a Slight Risk of excessive rainfall over parts of Northern New England and Central/Southern Rockies, and dangerous heat across parts of the Pacific Northwest, Middle Mississippi Valley, Central Plains, and Northeast Coast.

A quasi-stationary front extending from the Northeast to the Great Lakes, then roughly southwestward to the Central High Plains, will slowly move to Southern New England to the Ohio Valley and the Southern Plains by Tuesday.

Moisture pooling along the front will aid in producing showers and thunderstorms over parts of the Great Lakes/Upper Mississippi Valley to the Central High Plains that will move eastward with the front through Tuesday. 

Some of the storms will produce heavy rain. Therefore, The Weather Prediction Center (WPC) has issued a Moderate Risk of excessive rainfall with these thunderstorms over parts of the Upper Great Lakes and Upper/Middle Mississippi Valley through Monday morning. The associated heavy rain will create numerous areas of flash flooding. Many streams may flood, potentially affecting larger rivers.

Furthermore, monsoonal moisture will trigger diurnal showers and thunderstorms with heavy rain over parts of the Southwest and the Central/Southern Rockies on Sunday. Therefore, the WPC has issued a Slight Risk of excessive rainfall over parts of the Southwest and parts of the Central/Southern Rockies and Central High Plains through Monday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable.

On Monday, the front will extend into the Northeast, producing showers and thunderstorms with heavy rain over parts of the region. Therefore, the WPC has issued a Slight Risk of excessive rainfall with these thunderstorms over parts of Northern New England 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.

The excessive rainfall threat decreases to a Marginal Risk on Tuesday from the Northeast to the Middle/Lower Mississippi Valley.

In addition, monsoonal moisture will continue to trigger diurnal showers and thunderstorms with heavy rain over parts of the Central/Southern Rockies on Monday. Therefore, the WPC has issued a Slight Risk of excessive rainfall over parts of the Central/Southern Rockies 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.

On Tuesday, the threat of excessive rainfall will move southwestward over parts of the Southwest and Great Basin. Therefore, on Tuesday, the WPC has issued a Slight Risk of excessive rainfall over parts of the Southwest/ Great Basin and Southeastern California. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable.

Meanwhile, a weakening upper-level high over the Central Plains and Middle Mississippi Valley will aid in allowing temperatures to reach into the upper nineties to low hundreds over the region and along with high humidity, have prompted Heat Advisories over parts of the Middle Mississippi Valley and Central Plains through Sunday evening. 

Weak ridging over the Northeast will allow temperatures to rise into the low to mid-nineties and dew points in the upper sixties to low seventies have prompted Heat Advisories over parts of the Northeast Coast to parts of Lake Ontario through Sunday evening, too.

However, upper-level ridging will increase over the Pacific Northwest on Monday. The ridging will allow the temperature to rise into the mid-nineties to mid-hundreds prompting Excessive heat warnings and Heat Advisories to start from noon local time on Monday into late on Tuesday.