Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 312 AM EST Wed Dec 23 2015 Valid 12Z Wed Dec 23 2015 - 12Z Fri Dec 25 2015 ...Rain and mountain snow expected to continue over much of the western U.S. through Christmas Eve... ...Widespread anomalous warmth expected east of the Rockies... ...Numerous showers and thunderstorms are likely from the Gulf Coast to the northeast states... The next two days will be featured with a progressive flow pattern aloft that will result in rapidly moving shortwave disturbances from southwest to northeast across the nation. In addition, ridging aloft and at the surface is expected to develop over the eastern U.S., and a trough over the western U.S. along with colder weather over the Intermountain West and Rocky Mountains. A series of storm systems and onshore flow will continue to affect the Pacific Northwest through Thursday. Periods of coastal rain and heavy mountain snow can be expected, with the greatest amounts likely over the Cascades and northern and central Rockies where amounts in excess of one foot are likely at the highest elevations. By the end of the forecast period on Christmas morning, precipitation is expected to become more scattered across the western U.S. with less storminess directly impacting the West Coast. Many locations across the Rockies and northern Intermountain West are likely going to enjoy a white Christmas this year. The same certainly can not be said for the eastern U.S., with the exception of northern Minnesota, northern Michigan and parts of northern New England. A December heat wave is expected for most locations along and east of the Mississippi River, with numerous record highs expected. Large scale southerly flow from the tropics, along with the jet stream being much farther north than usual, will result in spring-like warmth and humidity all the way to the Great Lakes and parts of New England going through Thursday. Expect widespread 60s and 70s for daytime highs, and 50s and 60s for overnight lows for much of the eastern U.S. through Thursday. Some locations across the southeastern U.S. will likely reach 80 degrees between now and Christmas Day! In addition to the warmth and humidity, widespread rainfall is also in the forecast from the Gulf Coast to the Ohio Valley where amounts on the order of 1 to 3 inches is likely. Excessive rainfall outlooks are in effect for parts of these areas, where flash flooding could be an issue. Severe thunderstorms are also forecast to develop from the Deep South to the Ohio Valley on Wednesday ahead of a cold front. D. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php