Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 443 AM EDT Sun Apr 21 2013 Valid 12Z Sun Apr 21 2013 - 12Z Tue Apr 23 2013 ...Another Round of Snow and Cold for the Northern Rockies and High Plains... With the exception of the Florida peninsula and the immediate coastline of the Southeast--where a frontal zone will keep the chance of showers going through the short-range period--the East will be under the sheltering influence of a sprawling area of high pressure at the surface. Chilly nights are expected in association with this Canadian airmass, particularly over the interior Northeast and northern Mid-Atlantic region. The weather systems expected to have the most impact on the nation through early Tuesday will be an Arctic high pressure area dropping into the northern Rockies, and a cool, moist disturbance streaking across the Pacific Northwest. These two features will combine to produce another round of wintry weather from the northern Intermountain Region to the central and northern Great Plains. At first, the snow and cold will be confined to areas astride the northern Continental Divide. By early Monday evening, an area of snow is expected to drop through the central high plains attendant to the Arctic air nosing southward, with a second area of snow on the backside of a developing frontal wave over the upper Mississippi River valley. Showers and thunderstorms are expected to erupt along the leading edge of the Plains' system Sunday evening through Monday night--mostly west of the Mississippi. Cisco Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php