Multiple showers and thunderstorms will form Sunday across the US while the central region remains unseasonably hot. In the Southeast, a stalled frontal boundary will stretch from the lower Mississippi River valley through the mid-Atlantic states. Onshore flow from the Gulf of Mexico will feed energy and moisture into this system, allowing widespread showers and thunderstorms to develop.
Flooding will remain of concern for the lower Mississippi River valley, as the region has seen continuous rain showers for nearly a week. To the north, a low pressure system moving through eastern Canada will continue pushing a cold front over the Great Lakes and into the Ohio River Valley. By Sunday evening, the leading edge of this system may reach into the Northeastern states. Expect more showers and thunderstorms to develop along this front.
Behind this system, a trough of low pressure moves off the northern Rockies and into the Northern Plains and upper Midwest. This will create a warm front that will produce moderate to heavy showers and thunderstorms across the Dakotas and Minnesota. These storms may turn severe over northern Minnesota with main threats of large hail and damaging wind gusts.
A ridge of high pressure dominates the Central and Southern Plains, as well as the mid-Mississippi River valley. This keeps the region sunny and hot, with high temperatures reaching into the lower 100s again. Excessive heat warnings will remain in effect for these areas.
Out West, monsoonal moisture over the Southwest maintains shower and thunderstorm development over the Four Corners. Heavy rainfall and severe storms are not anticipated.
In the Pacific Northwest, a low pressure system will dip in from the Gulf of Alaska and kick up a few showers over northwestern Washington by Sunday evening. Temperatures in the lower 48 states Saturday have ranged from a morning low of 37 degrees at Stanley, Idaho to a high of 108 degrees at Lawton, Okla.
Weather Underground: http://www.wunderground.com
National Weather Service: http://iwin.nws.noaa.gov