Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 501 AM EDT Fri May 15 2015 Valid 12Z Fri May 15 2015 - 12Z Sun May 17 2015 ...Spring storm system to impact western U.S. with rain, mountain snow and much colder temperatures... ...Flash flooding rains and severe storms expected for portions of the Plains today and Saturday... An expansive upper level storm system, currently centered over the Great Basin, will slowly make its way east over the next couple of days. The storm is unusually large for this time of year and is associated with plenty of cold air. In fact, maximum temperatures across parts of the Desert Southwest will only be in the mid-60s today, which is 30 degrees below mid-May normals. While the greatest departures from normal will be across the Southwest, temperatures along and west of the Rockies will also be well below normal through at least Saturday. The storm system will generate scattered thunderstorms across the Intermountain West with mountain snow from the Sierra Nevada mountains into the higher terrain of Utah, Colorado, Wyoming and Montana, primarily for elevations above 8,000 feet. To the east of the storm system impacting the West, warm and humid conditions will eventually overspread most of the U.S. from the Great Plains to the East Coast, except for New England and the Great Lakes who will struggle to get into the warm sector of the downstream frontal system. The heat and humidity will help to fuel severe thunderstorms and flash flooding, but mainly for the center of the country. The greatest potential for severe storms today will be from the Texas Panhandle into southern South Dakota with severe storm probabilities greatest from west Texas all the way to Canada for Saturday. Any of these storms will be capable of severe weather and heavy rain, but wet soils due to previous rainfall across Texas and Oklahoma will make these states especially vulnerable to flash flooding. Otto Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php