Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 256 AM EDT Mon Jul 13 2015 Valid 12Z Mon Jul 13 2015 - 12Z Wed Jul 15 2015 ...There is a threat for heavy thunderstorms and flash flooding across the Midwest, Ohio Valley into parts of the Middle Atlantic states... There is a moderate risk of severe thunderstorms over parts of the Upper Mississippi Valley across the lower Midwest and Ohio Valley... There is a slight risk of heavy thunderstorms over parts of the Northwest... A weak but persistent series of upper level disturbances will drift east southeastward from the Upper Mississippi Valley across the Midwest, Ohio Valley and Mid Atlantic states. These disturbances will help fire some showers and thunderstorms along a nearly stationary front extending from the Mid Atlantic across the Ohio Valley and Midwest. These period surges of showers and storms could produce some severe thunderstorms, first over the Upper Mississippi Valley and then toward the Ohio Valley and lower Midwest. The Storm Prediction Center has issued a moderate risk of severe thunderstorms for these areas over the next couple days and contact the SPC website for more information. On the warm side of the stationary boundary, typical hot and humid conditions will persist underneath a nearly stationary upper ridge centered over the Southern Plains. Heat advisories and excessive heat warnings are issued for portions of the Southern and Central Plains into parts of the Southeast and the lower to mid Mississippi Valley, where humid conditions to uncomfortable but not unusual conditions with temperatures in the 90s to near 100 degrees. Around the western periphery of the upper high over the south central United States, a monsoonal flow of moisture northward from the Southwest across the central Rockies with diurnally enhanced thunderstorms developing most likely in the late afternoon and evening. An upper trough off the West Coast will contribute to instability, aiding the development of afternoon thunderstorms especially across Oregon and Idaho. Some of these storms could be accompanied by locally heavy rain and the risk of flash flooding. Kocin Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php