Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 344 AM EDT Mon Aug 18 2014 Valid 12Z Mon Aug 18 2014 - 12Z Wed Aug 20 2014 ...There is a slight risk of severe thunderstorms over parts of the Middle/Upper Mississippi Valley... ...Heavy rain possible over parts of the Southwest... Upper-level low over Northern Plains will move eastward to the Upper Great Lakes while weakening. The system will produce showers and thunderstorms over parts of the Northern Plains and the Upper/Middle Mississippi Valley that will move eastward into the Great Lakes/Ohio Valley by Tuesday evening. In addition, a few upper-level impulses over the Lower Mississippi Valley and the Ohio Valley will move eastward to the Mid-Atlantic Coast by Tuesday. The energy will trigger showers and thunderstorms over parts of the Mid-Atlantic/Ohio Valley to the Lower Mississippi Valley/Central Gulf Coast will gradually move off the Southeast/Mid-Atlantic Coast by Tuesday evening. Meanwhile, upper-level energy over the Pacific Northwest will move southward along the West Coast to just off Southern California by Tuesday. The upper-level energy and monsoonal moisture will aid in producing showers and thunderstorms over parts of the Southwest and the Central/Southern Rockies that will spill over into parts of the Northern/Central Plains by Tuesday evening. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php