Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 253 PM EST Mon Dec 21 2020 Valid 00Z Tue Dec 22 2020 - 00Z Thu Dec 24 2020 ...Rain and higher elevation snow continue across the Pacific Northwest through tonight before snow spreads eastward... ...A round of light snow and rain will affect the Midwest toward the northern Mid-Atlantic/Northeast through early Tuesday... One more wet day is in store for the the Pacific Northwest today, as Pacific moisture continues streaming in. Given wet antecedent conditions, the additional rain could lead to isolated minor river flooding, ponding on roadways, and the possibility for landslides. Then by this evening, a strengthening low pressure system is forecast to track near the northwestern U.S./southwestern Canadian border and sweep a cold front across the Northwest states. This will lower snow levels and then spread precipitation farther east as the front moves through the Great Basin and Rockies by Tuesday. Precipitation in the form of snow is expected in the Great Basin and Rockies, with some mixing of rain in lower elevations of the Northern High Plains. Snow totals should be highest in higher elevations, with snow of 6 to 12 inches with locally higher amounts across the Northern Rockies, Sawtooth Mountains/Bitterroots, and Wind River Mountains/Tetons. Then this system will spread light precipitation into parts of the central U.S. late Tuesday into Wednesday. Another low pressure system is forecast to move across the Great Lakes today into tonight, accompanied by light rain, mixed precipitation, and/or snow depending on the area over the Upper Midwest, Great Lakes region, Upper Ohio Valley, the northern Mid-Atlantic, and the Northeast. Snow amounts should generally be light, but the Central Appalachians could see 6"+ of snow as upslope flow enhances the totals. Elsewhere, some light rain showers could linger today across southern Florida along a cold front. Temperature-wise, the contiguous U.S. will see around average or above average temperatures almost everywhere today, with Florida being a cooler than normal exception. The most anomalous temperatures are expected for the Northern/Central Plains, with highs 15 to as much as 30 degrees above average through Tuesday. Cooler air should spread into the Northwest Tuesday behind the cold front and progress into the Rockies Wednesday. Hamrick/Tate Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php