Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 246 AM EST Sun Nov 22 2020 Valid 12Z Sun Nov 22 2020 - 12Z Tue Nov 24 2020 ...Low pressure system produces rain over the Ohio Valley and Lower Great Lakes... ...Air Stagnation Advisories over parts of Oregon; rain and mountains snow returns to the Pacific Northwest Sunday/Monday... ...Light snow and scattered freezing rain will change over to rain over parts of the Northeast... Low pressure over the Ohio Valley will move northeastward into Eastern Canada by Monday evening. The system will produce snow over parts of Michigan on Sunday morning. Also the storm will produce light snow and pockets of freezing rain over parts of the Northeast that will change over to rain overnight Sunday. The snow and freezing rain will produce hazardous driving conditions. By Monday morning, rain will extend from the Northeast to parts of the Mid-Atlantic. Meanwhile, another boundary moving eastward from the Northern Plains will move into the Upper Great Lakes producing rain and snow on Sunday. On Sunday afternoon, snow will merge with the western edge of the eastern system by Monday morning. Scattered snow showers will continue over parts of the Northeast Monday night into Tuesday. Additionally, upper-level ridging over the Northwest will give way to upper-level trough as multiple fronts move into the Pacific Northwest. The ridging and surface high pressure will aid in producing stagnant air over parts of Oregon through Sunday afternoon. Air Stagnation Advisories have been posted over parts of Oregon through Sunday afternoon. As the systems move on shore, rain will develop over parts of the Northwest on Sunday evening. As the precipitation moves inland, higher elevation snow and lower elevation rain will develop over the interior of the Northwest. On Monday snow will move into parts of the Northern Intermountain Region and Great Basin. The snow will begin to wane on Tuesday morning. Likewise, the snow will aid in producing hazardous driving conditions. Furthermore, upper-level energy and weak moisture will aid in producing higher elevation snow and rain over parts of the Central Rockies and the Southern High Plains overnight Monday into Tuesday. Once again, the snow will aid in producing hazardous driving conditions. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php