Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 341 AM EST Thu Nov 20 2014 Valid 12Z Thu Nov 20 2014 - 12Z Sat Nov 22 2014 ...Arctic air will hold a grip on the central and eastern U.S...but temperatures should begin to moderate heading into the weekend... ...Heavy snow bands will continue to set up downwind of the Lower Great Lakes... ...Accumulating snows expected in the Cascades late this week... ...Precipitation will make a return to Texas and the Lower Mississippi Valley... Arctic air will continue to hold a grip on the central and eastern U.S....but the below normal temperatures from the Great Plains to the Atlantic Coast should begin to moderate heading into the weekend. Within the frigid airmass...strong winds in the wake of a clipper system lifting into Canada should ramp up lake effect snows on Thursday...with the heaviest snow bands expected to set up downwind of the Lower Great Lakes. Snow showers across the Great Lakes should begin to diminish on Friday as a strong surface high slides eastward and centers itself over the Ohio Valley. A series of Pacific systems will bring unsettled weather into the Western U.S. late this week. The first system moving onshore will cause moderate rains and mountain snows across northern California on Thursday before weakening while dropping towards the Southwest on Friday. A second...more robust...Pacific system approaching the coast will spread precipitation into the Northwest by early Friday. Pacific moisture streaming inland...combined with orographic effects...should cause heavy rains along the Washington and Oregon coasts and accumulating snows in the higher elevations of the Cascades and northern Rockies. Across the southern tier of the Nation...moisture surging northward out of the Western Gulf will fuel increasing amounts of shower and thunderstorm activity across Texas and the Lower Mississippi Valley on Thursday and Friday. Some storms could be strong to severe...and as the moisture and precipitation spread northward over a dense Arctic airmass...freezing rain will be possible for portions of the Central Plains and Middle Mississippi Valley. Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php