Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 406 AM EST Fri Dec 13 2013 Valid 12Z Fri Dec 13 2013 - 12Z Sun Dec 15 2013 ...A complex storm system will impact much of the Central and Eastern U.S. this weekend... A complex storm system impacting much of the Central and Eastern U.S. this weekend will be the main focus during the short range period. Widespread precipitation is expected to develop from the Southern Plains to the Great Lakes on Friday as energy aloft swings out of the Southwest and surges moisture northward out of the Gulf of Mexico. On Saturday...precipitation will spread into the Eastern U.S. while the energy aloft...and associated surface low...quickly lift northeastward through the Tennessee and Ohio Valleys. Rain...with a few rumbles of thunder...will be the main precipitation type across the southern tier...but sub-freezing temperatures already in place...combined with another arctic boundary sinking through the Nation...will complicate precipitation types farther north. A wide swath of accumulating snows are expected across the Ohio Valley...northern Mid-Atlantic States...and into the Northeast. To the south of the snow...a wintry mix of snow...sleet...and freezing rain will be possible...especially in locations just east of the Central Appalachians that will be wedged in the cold air. Out West...weak energy dropping southeastward will trigger light showers across the Pacific Northwest and Northern Rockies on Friday...but upper ridging building in behind the system should keep weather fairly quiet for locations west of the divide this weekend. Gerhardt Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php