Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 354 PM EST Sat Jan 03 2015 Valid 00Z Sun Jan 04 2015 - 00Z Tue Jan 06 2015 ...A storm deepening over the Lower Great Lakes will bring widespread unsettled weather to the Eastern U.S. on Sunday... ...Heavy rains and mountain snow expected to move into the Pacific Northwest and Northern Rockies... A surface low initially over the Middle Mississippi Valley will quickly deepen while tracking towards the Lower Great Lakes Saturday night. A rich supply of Gulf moisture pulling northward will fuel heavy rains and strong to severe thunderstorms ahead of the trailing cold front crossing the Appalachians on Sunday. Farther north...a wide band of precipitation is expected to the north of an associated warm front inching northward through the Mid-Atlantic states and Northeast. Initially...precipitation could start off as snow...but it should quickly transition to sleet...freezing rain...and eventually all rain as warm air surges northward. Conditions should clear out up and down the Eastern Seaboard on Monday as the deepening storm lifts towards the Canadian Maritimes and the trailing cold front pushes well offshore; However...cool air and strong winds behind the departing storm will allow Lakes Effect snows to linger across the Great Lakes. Behind the storm...strong high pressure moving in from Canada will spread a fresh batch of Arctic air across much of the Central and Eastern U.S.. Conditions will become increasingly unsettled over the northwestern corner of the Nation as a strong Pacific system moves onshore over British Columbia. A plume of Pacific moisture streaming inland ahead of the system will allow for heavy rains along the Washington and northern Oregon coasts...with significant snowfall accumulations expected in the higher elevations of the Cascades. As the Pacific system drops southeastward and moisture reaches farther inland...snows should develop over the Northern Rockies and adjacent High Plains. Gerhardt Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php