Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 348 AM EDT Mon Aug 20 2018 Valid 12Z Mon Aug 20 2018 - 12Z Wed Aug 22 2018 ...Heavy rain and severe weather expected across the Mississippi Valley today... ...Active weather returns for the East Coast this week... ...Air quality remains a concern for parts of the Western U.S... A low pressure system will continue to lift out of the Plains and move into the Mississippi Valley today. Ahead of the system, warm and moist air will be transported from the Gulf of Mexico ahead of the frontal boundaries associated with this system. Showers and thunderstorms will persist across the lower and middle Mississippi Valley, along with scattered showers and thunderstorms occurring throughout the Southeast, Tennessee and Ohio Valleys. Some of these thunderstorms have the capability of producing severe weather where the Storm Prediction Center has a slight risk along the Tennessee and Mississippi Valley. The heaviest axis of rainfall will fall along Iowa and southern Wisconsin today. By Tuesday, the low pressure system will quickly progress eastward toward the East Coast. Areas from the Northeast southward into the central Gulf Coast can expect convection along and ahead of the front. Some of these storms could become severe--thus, SPC has highlighted a slight risk of severe weather for parts of the Ohio Valley into the Mid-Atlantic. Moderate rainfall will also be anticipated for the Great Lakes as the surface low lifts over this area. By Wednesday, most of the precipitation will move offshore; however, as the front presses across New England--showers and thunderstorms will follow. Fire weather risks continues to be elevated especially for the Pacific Northwest, Intermountain West and portions of the Great Basin through Tuesday. Red flag warnings are in effect for parts of these areas. Air quality also remains a concern due to the smoke from ongoing fires. Air Quality Alerts continue to be in effect for much of the Pacific Northwest and all of Montana. Elsewhere, moisture will surge back into the Southwest by Tuesday. Late afternoon and early evening thunderstorms will return across the Southwest and Great Basin on Tuesday and Wednesday. Some of these storms could produce flash flooding especially in favorable terrain and urban areas. On Tuesday night and into Wednesday, thunderstorms are expected to develop in the High Plains of Colorado and Kansas and move into the southern Plains. Some of these areas have received above normal rainfall in the last week, elevating the chances of localized flash flooding. Additionally, there is a slight risk of severe weather in a small area of southeast Colorado and the Oklahoma Panhandle. Reinhart Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php