Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 353 PM EDT Wed May 20 2020 Valid 00Z Thu May 21 2020 - 00Z Sat May 23 2020 ...There is a high risk of excessive rainfall over the Southern Appalachians, heavy rain to drench the southern Mid-Atlantic... ...Daily episodes of severe weather to transpire in the High Plains, critical fire weather conditions linger across portions of the Southwest and Four Corners Region... ...Showers, mountain snow, and below normal temperatures in the Northwest... A stalled upper-level low over the Mid-South continues its onslaught of heavy rain over the southern Appalachians and Mid-Atlantic. Rainfall rates will become excessive within bands of embedded thunderstorms. The storm's seemingly endless supply of moisture, its slow movement, and the region's overly saturated soil are a recipe for significant flooding tonight and into Thursday. Flash Flood Watches remain in effect for parts of the eastern Ohio Valley, southwest Virginia, and much of the western Carolinas. High risks for excessive rainfall are forecast for the Southern Appalachians of North Carolina and southwest Virginia through Thursday morning where widespread flash flooding is likely. Landslides and debris flows are possible within steeper terrain. Storm total rainfall amounts could exceed ten inches in parts of the southern Appalachians. A few severe storms are possible along the coastal Carolinas and into southern Georgia this evening and into Thursday. In addition, brisk onshore winds responsible for coastal flooding in the Virginia Tidewater, the lower DelMarVa Peninsula, and North Carolina Outer Banks will gradually weaken overnight. In the Heartland, rounds of severe storms are expected to develop up and down the Great Plains this evening and through Friday. This is due to the combination of a slow progressing frontal boundary to the north and the dry line to the south acting as triggers for thunderstorms up and down the High Plains this evening and again on Thursday. The front's slow progression could also lead to flash flooding concerns in areas impacted by heavy thunderstorms. To the south, dry and windy conditions will prevail across the Southwest, promoting elevated to critical fire weather conditions across much of the Southwest through through Friday. In the West, an upper level trough is swinging through the northern Rockies this afternoon with scattered heavy showers and thunderstorms dotting parts of the Northwest. Rainfall rates could be heavy enough to cause flash flooding this evening. As a result, a slight risk for excessive rainfall is in place for parts of eastern Oregon and Washington, northern Idaho, and northwest Montana through early Thursday morning. As this upper low heads north into the Canadian Prairies, another upper low will track into the Pacific Northwest on Thursday. This next storm system will be responsible for ushering in considerably cooler temperatures, numerous showers, and even some mountain snow for both Thursday and Friday. Mullinax Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php