Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Fri Aug 14 2020 Valid 12Z Fri Aug 14 2020 - 12Z Sun Aug 16 2020 ...Strong to severe thunderstorms across the northern Plains into the upper Midwest will result in locally heavy rainfall through Friday... ...Increasing threat of heavy rain expected from the central/southern Appalachians to the Mid-Atlantic during the weekend... ...Record heat becoming less intense over the southern Plains but spreading into the interior Pacific Northwest and Great Basin during the weekend... A low pressure system developing along a cold front with fairly vigorous dynamics will support the development of strong to severe thunderstorms across the northern Plains and the upper Midwest through tonight. In addition to the anticipation of severe weather, heavy downpours associated with the thunderstorms could lead to flash flooding for portions of these areas. The threat of severe weather and heavy rainfall should diminish on Saturday as the low pressure system moves away into Canada. Cool air ushering in behind the cold front will drop temperatures appreciably into the 50s across the northern Plains by Saturday morning. Meanwhile, a warm and moist air mass trapped to the south of a slow-moving frontal system will continue to provide a good chance of scattered thunderstorm activity from the lower Mississippi Valley eastward into the Mid-Atlantic and interior Southeast. As a weak low pressure system is forecast to form and then track slowly across the southern Appalachians, the threat of heavy rain is expected to increase across the central and southern Appalachians into the Mid-Atlantic during the next couple of days. On Friday and into Saturday, the central and southern Appalachians eastward have Slight Risks of flash flooding in place as upslope flow could enhance rainfall totals in the mountains, and much of the Carolinas/Mid-Atlantic have seen heavy rainfall recently so the ground is saturated. Meanwhile farther west, hot and mainly dry conditions are expected, though afternoon isolated storms could occur in the Southwest to the Southern/Central High Plains. Excessive Heat Warnings and Heat Advisories stretch from California through the Desert Southwest and into the Southern Plains, as temperatures above 100 degrees will be widespread, with temperatures over 110 degrees in the Desert Southwest. Dozens of record high minimum and maximum temperatures should be tied or set for those areas through the weekend (and beyond). After a cool day today in the northwestern U.S., the upper-level ridge building will mean hot temperatures spread to the Pacific Northwest especially by Saturday. Another threat expected is fire danger, and Elevated to Critical Risks have been outlooked by the Storm Prediction Center for portions of the Great Basin into much of Wyoming through Friday. Red Flag Warnings are also in effect. Kong/Tate Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php