Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 439 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 under 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 track slowly across the interior Southeast, the threat of heavy rain is expected to increase across the central and southern Appalachians followed by the Mid-Atlantic during the next couple of days. While the heavy rainfall may not necessary be continuous through the period, any additional downpours will raise the possibility of flash flooding from the Carolinas to the Mid-Atlantic where the ground is already saturated from recent heavy rainfall. The low pressure system is forecast to edge slowly eastward toward the coast by Sunday morning, with the heaviest rainfall most likely moving across the interior Mid-Atlantic. In contrast to the wet weather in the East, hot and mainly dry conditions are expected to continue for the western U.S. under the dominance of a warm ridge of high pressure. A large area of Excessive Heat Warnings and Heat Advisories is in effect from California through the Desert Southwest and into the southern Plains where record high minimum and maximum temperatures will be widespread. Only some afternoon isolated storms are forecast today for the interior Southwest to the southern and central High Plains. The heat is forecast to become less intense over the southern Plains but will intensify quickly across the interior Pacific Northwest and Great Basin during the weekend. In addition to the heat, dry conditions will promote fire danger across portions of the Great Basin into much of Wyoming today. Red Flag Warnings are also in effect. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php