Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 357 PM EST Sun Jan 04 2015 Valid 00Z Mon Jan 05 2015 - 00Z Wed Jan 07 2015 ...An Arctic airmass will continue to plunge temperatures across the central and eastern U.S.... ...Snowfall accumulations will pile up downwind of the Lower Great Lakes... ...Heavy rains and mountain snow expected in the northwestern corner of the Nation... ...A clipper system will streak snows from the northern Plains to the northern Mid-Atlantic states... Conditions will begin to dry out along the Eastern Seaboard Sunday night as a deep surface cyclone over southeast Ontario lifts towards the Canadian maritimes and the trailing cold front pushes off the Atlantic coast. Behind the system...an Arctic airmass that already invaded the north central U.S. will spread southeastward...plunging temperatures from the Mississippi Valley to East Coast. The cold air blowing over warmer waters will allow snow showers to crank up across the Great Lakes region...especially downwind of Lake Ontario and Erie. A rich plume of moisture streaming inland ahead of a Pacific system crashing into British Columbia Sunday night will fuel widespread precipitation across the northwestern corner of the Nation early this week. Heavy rains are expected along the Washington coast while snowfall accumulations in excess of a foot will be possible in the Cascades and northern Rockies. Energy dropping out of Western Canada will streak a weak wave of low pressure from the northern Plains to the northern Mid-Atlantic Monday into Tuesday. The clipper system will be quite moisture starved; However...a fresh surge of Arctic air across the Central and Eastern U.S. will allow for a swath of accumulating snows to the north of the low track. Gerhardt Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php