Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 347 AM EDT Sun May 08 2016 Valid 12Z Sun May 08 2016 - 12Z Tue May 10 2016 ...Strong to severe thunderstorms possible from the southern and central Great Plains to the lower and mid Mississippi valley... ...Heavy rainfall accumulations possible from the lower Missouri to the mid Mississippi valleys... ...Locally heavy snows possible for portions of the northern Rockies late Monday into Tuesday... A broad upper low currently centered over the Great Basin and southwestern U.S. is expected to slowly lift northeastward this period. Scattered showers and thunderstorms are forecast to continue on Sunday from the Sierra eastward to the central and southern Rockies, with precipitation expected to end by early Monday across California and much of the Great Basin as the aforementioned low reaches the central Great Plains. Further to the east, southerly winds are expected to draw moist, unstable air from the Gulf of Mexico -- increasing the threat for strong to severe thunderstorms across portions of the southern and central Great Plains on Sunday. On Monday, the threat is forecast to shift further east, extending into portions of the lower and mid Mississippi valley. The greatest potential for heavy rainfall accumulations is expected center across the lower Missouri and mid Mississippi valleys. Moisture advecting from the south is forecast to focus along a slow moving frontal boundary, supporting heavy rains across the region. A well-defined cold front is expected to push southeastward across the northwestern U.S. this period. In addition to keeping high temperatures several degrees below normal across the northern Rockies and high plains on Monday and Tuesday, locally heavy mountain snows are forecast to develop along the southwestern Montana and northwestern Wyoming ranges Monday night into Tuesday. Across the Northeast, a strong low moving across southeastern Canada is expected to usher in cooler temperatures and another chance for showers and thunderstorms early Sunday. Further to the south, scattered showers and thunderstorms are forecast to focus near a frontal boundary dropping into the region. Meanwhile, high pressure and dry conditions are likely to prevail across the Southeast. Pereira Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php