Weather across America

(NATIONAL) Excessive heat and fire weather concerns continue to impact a large portion of the West and northern High Plains, Heavy rain and the threat of flash flooding extends from southern New England to the western Gulf Coast, and isolated severe thunderstorm and flash flood chances over the Southwest.

Similar to the last few days, excessive and record-breaking heat will continue to be found throughout the western United States and remain the case through at least midweek. Underneath a strong upper-level high anchored over the central Great Basin, high temperatures are forecast to soar well above average and into the triple digits. The heat is expected to further increase in severity on Tuesday, with temperatures potentially reaching into the 110s throughout the Central Valley region of California. 

These highs in California will likely threaten monthly temperature records and be particularly dangerous for vulnerable residents. Record heat will also include much of the central Great Basin and northern Rockies, with highs into the upper-90s stretching as far east as the northern/central Plains. Excessive Heat Warnings and Heat Advisories have been issued for a majority of California and Nevada, as well as parts of Arizona, Utah, and Idaho.

Additionally, scorching heat combined with low relative humidity and gusty winds may lead to critical fire weather conditions Sunday over parts of the Great Basin. Favorable conditions for wildfires to develop and spread uncontrollably also extends into the northern Rockies and northern High Plains, where Red Flag Warnings have been issued. Residents and visitors are urged to follow proper heat safety and fire restrictions.

For the Gulf Coast and eastern third of the Nation, heavy rain and scattered instances of flash flooding will remain a concern through the first half of the week. An elongated upper-level low stretching over the middle and lower Mississippi valleys will aid in producing numerous showers and thunderstorms over the Ohio and Tennessee valleys through Labor Day. Some storms may be slow-moving and produce intense rainfall rates, which could lead to flash flooding. 

A Slight Risk (level 2/4) of Excessive Rainfall has been issued for much of this region Sunday and Tuesday, as well as into parts of the southern Appalachians. Heavy rain is also possible along a cold front as it slides southward from the Northeast to the northern Mid-Atlantic by midweek. A few inches of rainfall within a short period of time could produce scattered flash floods on Monday from southern New England to the central Appalachians, including most of Pennsylvania.

For the Gulf Coast, a stagnant and tropical airmass will generate additional chances for downpours Sunday, with the threat of more widespread heavy rain shifting to the western Gulf Coast and South Texas by Labor Day. As a result, a Slight Risk of Excessive Rainfall is in effect Sunday and Monday over South Texas and the Lower Texas Coast. 

Elsewhere, isolated showers and thunderstorms throughout the Southwest could lead to damaging wind gusts and flash floods. The greatest threat is expected to reside over southern California and the Mojave Desert region, where marginal risks for severe weather and excessive rainfall are in effect.