Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 225 PM EST Sun Dec 20 2015 Valid 00Z Mon Dec 21 2015 - 00Z Wed Dec 23 2015 ...Storminess to continue in the northwest U.S...while shower chances along with unseasonably mild weather return to areas east of the Mississippi river... The next couple days will continue to be dominated by fast nearly zonal flow that will gradually buckle as very strong jet energy begins to carve out a deepening upper trough through the central and southern Rockies by late Tuesday. Cold air will continue to be held at bay, mainly across southern Canada with some brief intrusion into the northern border states. Otherwise, above normal temperatures will continue to dominate much of the central and eastern U.S. during the next 2 days. Pacific onshore flow conditions will be enhanced by a series of quick moving systems that will move eastward across the eastern Pacific bringing additional rain and higher elevation snows to much of the northwest U.S. A lead frontal system will quickly move through the Pacific Northwest early Sunday night before weakening rapidly through the mountainous terrain..but not before bringing some decent snows to some of the more favored westward facing mountain terrain. By Monday morning another deepening area of low pressure heading toward the Washington coast will bring a renewed round of rain and snow along with strong winds into the region as the associated cold front settles southward into California, bringing much needed rain and mountain snows into the northern half of the state. A third system approaching the Pacific Northwest on Tuesday will bring additional precipitation into the northwest and southeastward into the central and southern Rockies as associated strong upper jet helps carve out a deepening upper trough over the region. To the east, a series of low pressure systems riding northeastward along a cold front pushing eastward across the Midwest and Mississippi Valley Sunday night will bring increasing chances of showers to much of the eastern U.S. through Tuesday as warmer and increasingly moist air is drawn northeastward from the Gulf of Mexico. The main low pressure system will push off the New England coast late Tuesday, but any cooling behind the associated cold front will be rather brief with more unseasonably mild air expected to return from the south beyond this period. Sullivan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php