Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EST Fri Dec 18 2020 Valid 12Z Fri Dec 18 2020 - 12Z Sun Dec 20 2020 ...Lower elevation rain and higher elevation snow continues across the Northwest... ...Light snow is possible across the Central Rockies/High Plains and Great Lakes region, while showers/thunderstorms will affect the south-central U.S. beginning late Friday... Rounds of precipitation are once again likely across the northwestern U.S. through the weekend as a couple of frontal systems pass through, directing Pacific moisture into the region. Coastal and lower elevation rain is expected, along with higher elevation snow. Rain amounts along the Washington and Oregon coast could be sufficiently heavy enough to cause some flooding concerns especially Saturday. Meanwhile, snow totals through Sunday morning could reach 2 feet in the highest elevations of the Washington Cascades, while areas of the Northern Rockies could see 6 to 12 inches of snow. An upper-level trough is forecast to move fairly quickly across the Intermountain West today, into the central U.S. Saturday, and toward the Ohio Valley by Sunday morning. Associated with this trough, some light snow is possible across the Central Rockies today, while light mixed precipitation could also spread across the Central Plains. Then tonight into Saturday, rain showers and thunderstorms are expected to increase across the southern portions of the Plains and Mississippi Valley as Gulf of Mexico moisture increases ahead of a frontal system. Also, farther north, a round of light snow could affect the Upper Midwest today, and light snow and/or rain could spread into the Great Lakes region Saturday. Snow totals should remain less than 2 inches there. Precipitation is forecast to push eastward into the Ohio and Tennessee Valleys late Saturday and toward the Eastern Seaboard Sunday. In the East, the historic nor'easter has pulled away from the coast, and high pressure will build in behind it. This cool high will lead to below normal temperatures for the Eastern Seaboard, likely staying below freezing in much of the Northeast Friday and Saturday due to the high and the snowpack. The Intermountain West can also expect below normal highs today, while in between across the central U.S., temperatures of 10 to 15 degrees above average are forecast. Tate Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php