Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EST Fri Nov 20 2020 Valid 00Z Sat Nov 21 2020 - 00Z Mon Nov 23 2020 ...Rain will develop from the central Plains to the Ohio Valley this weekend... ...Wintry precipitation expected across the Great Lakes into interior New England this weekend... ...Air Stagnation Advisories over parts of Oregon... A front extending across the central Plains to the lower Great Lakes will remain nearly stationary through Saturday night. As a low pressure wave develops near the frontal boundary, rain is expected to expand across the central Plains into the Midwest on Saturday with embedded thunderstorms. By Sunday morning, the low pressure wave is forecast to intensify and track along the front toward the Ohio Valley. The low will pull down colder and drier air from the north and taper off the rain in the central Plains as a steady rain moves across Ohio Valley and into parts of the central Appalachians later on Sunday. Some wintry precipitation will also develop over the upper Midwest Saturday night and then spread eastward across the Great Lakes reaching interior New England by Sunday evening. Temperatures will cool down closer to normal across the northern tier states behind the cold front but very mild conditions for late November will continue across the southern tier states into much of the East Coast where temperatures will range from 10 and 15 degrees above average. A somewhat less active pattern off the Pacific Northwest will bring a slight break to the unsettled weather across the region. However, weak disturbances moving onshore will result in additional rain and higher elevation snow over parts of northern Washington to northwestern Montana during the weekend. Meanwhile, upper-level ridging will slowly build over the Northwest; and with high pressure at the surface, the air over parts of Oregon will become stagnate. Air Stagnation Advisories have been posted over parts of Oregon Through Sunday. The next wave of moisture is forecast to reach the coastal region later on Sunday. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php