Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 457 PM EDT Sat May 09 2015 Valid 00Z Sun May 10 2015 - 00Z Tue May 12 2015 ...Multi-day severe weather/flash flooding event to affect the Plains and Mississippi Valley... ...Late season heavy snowfall expected over the Rockies and into High Plains... ...Heavy rainfall likely in response to Tropical Storm Ana across the Carolinas... A potent upper low currently moving through the Four Corners region will be the focus for severe weather, potential flash flooding, and heavy snow across the higher terrain and adjacent High Plains. Abundant low-level moisture lifting out of the Gulf of Mexico has kept convection quite active this afternoon with this theme continuing the next couple of days. The primary threat area for severe weather and flash flooding through Sunday morning will be located across the Southern/Central Plains and extending back toward the adjacent High Plains of eastern Colorado and western Kansas. Based on the latest convective outlook from the Storm Prediction Center, tornadoes and large hail appear to be the dominant severe threats with damaging wind possible as the convection becomes more linear in nature. This severe weather threat will migrate eastward by the following day into the Mississippi River Valley and back toward the Arklatex. Meanwhile, heavy rainfall with these thunderstorms will raise the risk for flash flooding, particularly over regions with saturated soils from the multi-day rainfall event. Additionally, other areas of the Southern/Central Plains may see slow cell motions or repeat convection also enhancing the risk for flash flooding. Given the anomalous nature of the upper low lifting from the Four Corners region to the Central High Plains, a major Spring snowstorm should affect the Central Rockies and into the Northern/Central High Plains. This system has tremendous moisture feed into it which will aid in hefty snowfall amounts across these aformentioned regions. The latest WPC winter weather desk forecast indicates a widespread area of 12 to 18 inches are likely from eastern Wyoming into much of western South Dakota. The Black Hills may even see amounts approach 2 feet. This storm will also affect some of the major cities in the area including Denver, Cheyenne, and Rapid City. The first tropical system of the year, Tropical Storm Ana is currently spinning off the coastal Carolinas with gradual weakening expected as it leaves the warm Gulf Stream waters and makes its way inland by early Sunday morning. The stronger vertical motions are expected to straddle the coastline where the heaviest rainfall is being forecast. 2 to 4 inches of rain are likely just south of the Outer Banks with isolated heavier amounts possible. This system is expected to migrate north and eventually toward the northeast while continuing to weaken. Regarding temperatures, the deep upper trough moving through the Southern/Central High Plains will support well below normal readings the next couple of days. The current forecast suggests temperatures at least 25 to 30 degrees below normal for the second week of May which translates to highs in the upper 30s to lower 40s on Sunday across Wyoming and into western South Dakota. Meanwhile, underneath the upper ridge, warm weather will prevail across much of the eastern U.S. with highs well into the 80s into early next week. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php