Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 241 PM EDT Tue Apr 19 2016 Valid 00Z Wed Apr 20 2016 - 00Z Fri Apr 22 2016 ...Flash flooding possible for portions of the southern plains and western Gulf Coast states... ...Well above average temperatures expected for the northwestern U.S... An upper-level low and nearly stationary frontal boundary across the central U.S. will finally begin to move slowly eastward on Wednesday. In the meantime, showers and thunderstorms will continue for much of the southern/central plains and portions of the western Gulf Coast through tonight. Locally heavy rain will be possible, which may result in flash flooding for some areas. Farther west, snow showers will continue tonight for the higher elevations of the Rockies as energy associated with the upper-level low remains overhead. On Wednesday, the system will spread showers and thunderstorms into portions of the Upper Midwest and Great Lakes, as well as portions of the Ohio and Tennessee valleys. Locally heavy rainfall will remain possible on Thursday for portions of the lower and middle Mississippi valleys. By Thursday, the system will continue its slow movement eastward, and will spread showers and thunderstorms across the lower Great Lakes and into portions of the Northeast, as well as the Southeast. Across the West Coast, conditions will remain generally dry. Scattered showers and thunderstorms are possible across portions of the Pacific Northwest this afternoon/evening and again Wednesday. High pressure at the mid and upper-levels of the atmosphere will help to keep coverage of precipitation scattered, and will also keep high temperatures 10 to 25 degrees above average on Wednesday and Thursday. More widespread showers are forecast to begin spreading into the coastal Northwest by late Thursday as a Pacific frontal boundary approaches. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php