Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 304 AM EST Sun Dec 01 2013 Valid 12Z Sun Dec 01 2013 - 12Z Tue Dec 03 2013 ...Heavy snow and cold temperatures will impact the northwestern sector of the country... ...A potential coastal storm may bring moderate to heavy rainfall to the Outer Banks of North Carolina... The initial low amplitude mid-latitude flow is forecast to quickly amplify as a strong trof surges southward into the Pacific Northwest. Before this system moves into the U.S...there will be quite the anomalous moisture content in place over Oregon/Washington with origins in the tropical Pacific. This abundant moisture working in accordance with strong onshore flow should produce quite the precipitation event over the topography of Washington and stretching into Oregon. During the next couple of days, over a half a foot of precipitation is expected across much of the Cascades, with snow dominating later on as colder air arrives from the north. Through Tuesday morning, the WPC winter weather forecast suggests over a foot of snow over the Cascades with somewhat higher amounts possible further inland across the Bitterroots, Sawtooth, Northern Rockies over Montana, and the Tetons. The intensity of the precipitation should gradually diminish by early Monday as the powerful upper low drops down from British Columbia. The arctic frontal boundary accompanying this system will erode much of the moisture in place although snow should persist given the lift from the upper low itself along with the usual upslope effects. This change in air mass will be rather pronounced with temperatures falling in excess of 15 degrees Fahrenheit from Sunday into Monday. However, the bigger changes lurk just beyond this period entering early/mid next week. As this dynamic system impacts much of the Western U.S., a warm front at the surface will gradually lift northward as moisture return from the Gulf of Mexico commences by Monday afternoon. As the aforementioned upper low begins to dominate the Pacific Northwest, multiple impulses will slide eastward off this low center which will help spawn areas of rain/snow showers across the Northern Plains/Upper Midwest. The fact the precipitation will be of the mixed bag variety should limit the snowfall accumulations with only a widespread 2 to 4 inches expected through early Tuesday. Elsewhere, a developing coastal low may bring some impacts to the eastern seaboard. However, the heaviest precipitation is forecast to stay just off the coast although some impacts cannot be ruled out across the Outer Banks. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php