Weather across America

(NATIONAL) A Moderate Risk of Excessive Rainfall for parts of the Northeast, a Slight Risk of severe storms in southern New England, various areas of heavy showers and thunderstorms throughout the East & South, Excessive Heat Warnings and Heat Advisories from the Pacific Northwest to parts of the Southern Plains, and Air Quality alerts in effect over parts of the Northern High Plains, Midwest, and Great Lakes.

As day broke Sunday, copious amounts of moisture streamed ahead of a cold front slowly approaching from the west, igniting numerous heavy showers and storms from the Mid-Atlantic to the Northeast. These storms were capable of producing torrential rainfall rates and coincided within training areas of thunderstorms.

Given some parts of the Northeast contain saturated and sensitive soils from recent heavy rainfall over the past 10 days, this is a setup capable of producing significant flash flooding in affected areas. The Weather Prediction Center (WPC) has issued a Moderate Risk from the Delaware Valley on north and east into central New England. The Moderate Risk does include the NYC, Philadelphia, Hartford, and Boston metro areas. 

Potential impacts as a result of flooding include impassable roadways, swiftly flowing creeks and streams, and in higher terrain locations, possible mudslides. The Slight Risk area extends from the Virginia Tidewater on north to northern Maine. The Storm Prediction Center (SPC) also issued a Slight Risk for severe weather from the NYC metro area on east to include all of southern New England. 

Severe storms within the Slight Risk area may produce damaging wind gusts and tornadoes. While the Northeast faces the more significant threat for flash flooding Sunday, there are no shortage of other areas that are also at-risk for both Excessive Rainfall and severe weather. Sunday, SPC has a Slight Risk of severe storms in the Central Plains. 

Both WPC and SPC have Marginal Risks for Excessive Rainfall and severe storms that stretch from the Central Plains to the Middle Mississippi Valley. Both National Centers also feature Marginal Risk areas for the ArkLaTex and along portions of the Gulf Coast. By Monday, the threat for severe storms and excessive rainfall becomes more scattered across the country. 

SPC posted a Slight Risk for severe weather in southern South Dakota and northern Nebraska with a few Marginal Risks areas; one in the north-central Plains, one in central Montana, and the other in the Ohio Valley. When it comes to Excessive Rainfall, areas from the eastern Great Lakes on south to the Tennessee Valley could witness storms possibly cause areas of flash flooding. There are also Marginal Risks in Florida, the central Gulf Coast, and even southern Arizona.

Speaking of Arizona, "The Grand Canyon State" and many of its neighboring states in the West will continue to contend with an ongoing dangerous heat wave. In total, from South Florida and the Gulf Coast to the Southwest, over 80 million people remain under either an Excessive Heat Warning or Heat Advisory as of early Sunday morning. In the Southwest Sunday, daytime highs will approach the century mark in the interior Northwest, range between 100-110F throughout interior California and the Great Basin, and even top 115F in parts of the high desert of southern California, southern Nevada, and southern Arizona. 

Widespread record breaking high temperatures, as well as record breaking warm daily minimums are expected in parts of the Southwest, along the western Gulf Coast, and in South Florida. By Monday, the core of record breaking heat shifts more into the Four Corners states with parts of South Texas and South Florida still seeing possible record heat. The combination of sizzling temperatures and oppressively high dew points will result in sultry heat throughout the South into the upcoming week. 

For more information regarding both ongoing and potential impacts from this heat wave, please visit heat.gov. In addition to the flooding/severe threats and stifling heat, Air Quality alerts are in place for much of the Great Lakes, Midwest, and northern High Plains. This is due to the lingering thick concentration of Canadian wildfire smoke over these regions. While the concentration of smoke in the atmosphere should begin to wain by Monday, there is still enough smoke to support unhealthy air quality that is unhealthy for sensitive groups in parts of these regions into the start of the upcoming week.