Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 152 PM EST Mon Dec 24 2018 Valid 00Z Tue Dec 25 2018 - 00Z Thu Dec 27 2018 ...Heavy mountain snows likely across the Sierras, central Great Basin, and southern Rockies... ...Locally heavy rainfall possible across parts of the Northern California with flash flooding a threat mainly over burn scar areas... ...Post-Christmas winter storm to bring heavy snow to the north, heavy rain/strong thunderstorms to the south, and potential travel troubles across parts of the Central U.S. beginning Wednesday... A vigorous upper level system pushing into Northern California this evening will drop southward the next few days through the central Great Basin and into the Southwest. This system will spread rain across the lower elevations of California tonight and into the Southwest on Christmas Day. Locally heavy rainfall is possible, especially across parts of northern California tonight where flash flooding is a concern mainly over highly susceptible burn scar areas. This same system will bring heavy mountain snowfall from the California Sierra Mountains into the higher terrain of the central Great Basin and parts of the central and southern Rockies by Wednesday. As much as a foot or more of snow is possible in the highest elevations with winter storm warnings and winter weather advisories in effect for many of these locations. As this system emerges into the Plains towards the end of the short range, a significant winter storm is likely to develop across the Central U.S. by Wednesday. Heavy and accumulating snowfall looks to begin on Wednesday afternoon and evening across parts of the northern and central Plains, spreading eastward into the Upper Midwest and Great Lakes beyond the short range period. With plenty of instability in place along with ample Gulf moisture streaming northward ahead of the attendant cold front, heavy rainfall and strong to potentially severe thunderstorms are also possible in the warm sector across the Southern Plains. Both WPC and SPC have slight risks for excessive rainfall and severe thunderstorms, respectively, across parts of this region for Wednesday into Thursday. This storm is likely to make post-Christmas travel very difficult, if not impossible, across parts of the middle part of the nation beginning on Wednesday. Elsewhere, some light snow is possible across across parts of the Great Lakes and the Ohio Valley tonight into Tuesday in association with a pair of weak systems in the upper levels. Regarding temperatures in the short range, Christmas Day looks to be warmer than average east of the Rockies and ahead of the approaching winter storm. In the West, temperatures drop to below average Tuesday and Wednesday, with afternoon highs as much as 10 to 20 degrees below normal across parts of the Southwest. Santorelli Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php