Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Sun Aug 21 2016 Valid 00Z Mon Aug 22 2016 - 00Z Wed Aug 24 2016 ...Heavy rain could lead to flash flooding in southern Texas through tonight... ...Cooler and drier air will move in behinds showers and thunderstorms over the eastern U.S... ...Cooling trend expected for the Pacific Northwest... A cold front moving steadily eastward across the Appalachians this Sunday afternoon will bring a round of showers and thunderstorms along the Eastern Seaboard through tonight. New England will see these showers Monday morning before cooler and drier air behind the cold front overspreads much of the eastern U.S. under mostly sunny skies. The cooler temperatures will extend southwestward across the Mississippi Valley into Texas and southern Rockies where the trailing end of the cold front becomes stationary. Thunderstorms that form in southern Texas are expected to be slow-moving, and thus could lead to locally heavy rain and flash flooding through tonight. The stationary front will remain across the same areas on Monday and Tuesday but will begin to gradually weaken. Showers and thunderstorms should become more scattered in nature as the dissipating front slowly lifts northward into Oklahoma and Arkansas on Tuesday. Meanwhile, an upper-level trough is expected to amplify as it moves across British Columbia over the next couple of days. Cooler air associated with this trough will filter into and across the Pacific Northwest behind a cold front. The warm air ahead of the cold front will be pushed eastward into the northern Plains, where afternoon highs could approach the century mark on Monday. Little precipitation is expected ahead of the front until Tuesday afternoon when some strong thunderstorms could form in the Midwest. Meanwhile, monsoonal showers and thunderstorms are expected to continue in the central/southern Rockies. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php