Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 338 PM EDT Fri May 15 2015 Valid 00Z Sat May 16 2015 - 00Z Mon May 18 2015 ...Spring storm system to impact western U.S. with rain, mountain snow and below average temperatures... ...Flash flooding and severe thunderstorms expected for portions of the plains into Saturday... An expansive upper level storm system currently centered over the Great Basin, will slowly move eastward over the next couple of days. This storm system will bring widespread precipitation to much of the interior western U.S. over the next couple days. Scattered showers and thunderstorms will be possible at the lower elevations while snow will be possible at the higher elevations, generally above 8000 feet. Much colder air will move into the West in association with this storm system as well, with high temperatures from 10 to 20 degrees below average through the weekend across much of the interior western states. A warm, moist, and unstable air mass will remain in place across much of the central and eastern U.S. over the next couple days. Areas of showers and thunderstorms will be possible across a large portion of these regions. A relatively weak frontal system will move across the Lower Great Lakes this evening and toward the Northeast on Saturday. This system may produce a more focused area of rain and/or thunderstorms across portions of the Northeast tonight, with scattered showers and thunderstorms continuing into Saturday. A few areas of more widespread showers and thunderstorms will also be possible tonight across the plains as weak upper-level disturbances traverse the region. On Saturday, frontal system crossing the West today will begin to move into the central U.S., and a cold front at the surface will move from the Rockies into the plains. A more organized surface low pressure system will begin to develop across the plains Saturday night into early Sunday. A large area of widespread showers and thunderstorms is forecast to develop Saturday afternoon/evening extending from the southern plains to the northern plains. Flash flooding and severe thunderstorms are possible across areas of the plains tonight into Saturday. Please refer to products issued by the Storm Prediction Center for further details on the severe weather threat. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php