Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 326 PM EST Fri Dec 06 2013 Valid 00Z Sat Dec 07 2013 - 00Z Mon Dec 09 2013 ...A band of snow/sleet/freezing rain is expected from parts of the Lower Mississippi Valley to the Northeast... ...Temperatures will be 10 to 30 degrees below average from the Plains to parts of the Mississippi Valley... ...Rare snow for coastal Pacific Northwest... A strong cold front extending from the Mid Atlantic coast to the Central Gulf Coast will slowly push southeastward over the next two days before returning as a warm front at the end of the period. A strong surface temperature gradient, as much as 40 degrees, is accompanied by a strong upper level jet streak north and west of the front. Strong vertical velocities in vicinity of the jet are responsible for the moderate to heavy precipitation falling behind the front. A band of heavy snowfall will set up across portions of the Mid Mississippi Valley and Ohio Valley this afternoon with up to 10 inches of snow possible. A shallow layer of cold air in place across the Tennessee and Ohio Valleys is being overrun by milder air aloft leading to a prolonged period of freezing rain in the region. Precipitation should end as light snow as colder air filters in aloft. The precipitation shield is expected to consolidate along the cold side of the boundary as the upper-level jet max races off to the northeast this evening. By tomorrow morning, strong westerly flow over the Great Lakes will lead to the formation of snow bands downwind. The cold front in the east will push slowly southward before settling along the southeast coast late tomorrow. Rain showers will remain focus in vicinity of the front through the day. The front will begin returning as a warm front by Sunday morning with warm advection precipitation breaking out from the Tennessee Valley to the Southern Mid Atlantic. With cold air damming setting up in lee of the Appalachians, precipitation will begin as a wintry mix or snow across portions of central and southern Virgina and the higher terrain of the central Appalachians. In the west, a surface low pushing southward along the west coast will bring a reinforcing shot of cold air to the Pacific Northwest and later into southern California. Accompanied with the front will be a round of snow from southern Washington southward to Central California tonight. By tomorrow morning, snowfall is expected to overspread much of the Intermountain West with upslope flow locally enhancing snowfall totals. This surface low will eventually push out into the southern Plains toward the end of the period. In wake of the cold front pushing through the east, very cold temperatures are taking hold of much of the Nation. Temperatures will be 10 to 30 degrees below normal from the West Coast to the Mid Mississippi Valley. Krekeler Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php