Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 327 AM EDT Fri May 17 2019 Valid 12Z Fri May 17 2019 - 12Z Sun May 19 2019 ...Severe thunderstorms likely for much of the Great Plains on Friday...and reaching the lower and middle Mississippi Valley on Saturday... ...Heavy rainfall amounts and some flash flooding will be possible across portions of the Great Plains and Midwest... ...Much cooler than normal temperatures will continue for much of the western U.S. and the northern Plains... A rather strong upper-level trough of low pressure for this time of the year will advance across the western U.S. on Friday and then edge out across the Great Plains Friday night and Saturday where it will facilitate an area of surface low pressure in the lee of the Rockies. This will allow unsettled weather and very chilly temperatures to continue for much of the West and into the northern Plains. In fact, some areas will be cold enough for snow across the higher elevations of the Intermountain West, while valley locations see a chilly rain. High temperatures in some locations will be as much as 20 to 30 degrees below normal for Friday and Saturday, and this very cool and unsettled pattern should last generally through the weekend across the West. However, the approaching energy from the West and the developing area of low pressure in the lee of the Rockies is expected to set the stage for a fairly widespread area of heavy showers and thunderstorms Friday afternoon through Friday night, including a likelihood of severe weather, across a large area of the Plains. Two particular areas of focus include Nebraska and a separate area over west Texas. In both areas, the Storm Prediction Center currently has highlighted an Enhanced Risk of severe weather, with the expectation of thunderstorms producing very large hail, locally damaging winds, and possibly a few tornadoes. In addition to the threat of severe weather, heavy rainfall will locally result in concerns for flash flooding, and as a result the Weather Prediction Center has highlighted a Slight Risk of excessive rainfall across portions of the Midwest and also down across the southern High Plains. The threat of severe weather and flash flooding from heavy showers and thunderstorms will advance farther east across the central and southern Plains and also getting into the middle and lower MS Valley Saturday afternoon through Saturday night as the aforementioned low pressure in the lee of the Rockies advances east toward the Midwest along with its trailing cold front. Much of the Gulf Coast region and Southeast will be warm and dry over the next couple of days, at least until early Sunday when the upstream cold front begins to encroach on the lower MS Valley. Farther north, there will be a stationary front draped across the OH Valley and the Mid-Atlantic region, which will eventually begin to return north later in the weekend, but this front should be a focus for showers and thunderstorms, some of which will be capable of producing severe weather and localized flash flooding concerns. Orrison Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php