Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 1258 AM EST Fri Dec 15 2017 Valid 12Z Fri Dec 15 2017 - 12Z Sun Dec 17 2017 ...Pattern change expected over the weekend... The weather pattern over the continental U.S. will initially be featured with a broad eastern U.S. trough and a ridge centered near the West Coast. An upper level pattern change is likely by Sunday as multiple disturbances aloft break down the western U.S. ridge and more of a zonal flow pattern returns to the eastern states. A trough is expected to amplify over the Rocky Mountains during the weekend and increase the chance of snow for this region. After an extended period of dry weather, widespread accumulating snow is likely for the central and especially the northern Rockies over the next few days in response to a developing surface low over the Four-Corners region and shortwave energy aloft. Lake effect snow is also expected downwind of the Great Lakes at times. Warm and dry conditions are expected for Florida and especially the lower elevations of the Desert Southwest and into central and southern California. Fire weather concerns will still exist across parts of California owing to the dry conditions and gusty winds. On the other end of the temperature spectrum will be northern Minnesota and northern New England, where readings will remain quite chilly with highs in the teens and 20s. Thunderstorms are not expected across the continental U.S. until Saturday, when moisture returning northward from the Gulf of Mexico ahead of a front could fuel the development of some scattered storms for southeast Texas and Louisiana. D. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php