Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 413 AM EDT Sun May 17 2015 Valid 12Z Sun May 17 2015 - 12Z Tue May 19 2015 ...Moderate to heavy rains followed by snow for parts of the northern Great Plains and upper Midwest... ...Additional heavy rains possible for portions of the southern Great Plains and lower Mississippi valley... ...More late season precipitation for parts of California and the Great Basin... Low pressure organizing over eastern South Dakota Sunday morning is expected to track to the northeast across northern Minnesota later in the day. Moisture streaming north from the Gulf of Mexico is expected to wrap around the backside of this system, fueling moderate to heavy rains across parts of the Dakotas and Minnesota on Sunday. Before this precipitation comes to an end, anomalously cold air spilling out of Canada will afford a changeover from rain to a wintry mix, with some light snow accumulations possible across portions of the region. Further to the south -- southerly winds will continue to funnel warm, moist, unstable air up from the Gulf of Mexico, fueling showers and thunderstorms capable of producing heavy rains across portions of eastern Texas and Oklahoma into the mid and lower Mississippi valley early Sunday. Storms currently firing across this region are expected to weaken later today; however, there is the potential for some redevelopment across this region late Sunday into early Monday, with more heavy rains possible. By late Monday, the greater potential for storms is expected to shift further to the east into the Ohio and Tennessee valleys and the central Gulf Coast states. Further west -- precipitation is expected to develop across portions of the Pacific Northwest into California, primarily along the Sierra, and into the Great Basin, as another late season upper level low drops south along the California coast. By late Monday into early Tue, as this system begins to move inland across the Southwest, showers and thunderstorms with heavy rains may start to develop along the central and southern Rockies into the adjacent High Plains of eastern Colorado, New Mexico and the Texas Panhandle. Pereira Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php