Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 235 AM EST Sat Nov 17 2018 Valid 12Z Sat Nov 17 2018 - 12Z Mon Nov 19 2018 ...Snow possible over parts of the Upper Great Lakes, Central Rockies, Middle Mississippi Valley, and the Northern Mid-Atlantic into parts of New England... ...Air Stagnation and Air Quality Alerts continue to be in effect for parts of the Pacific Northwest and California... A front over parts of the Great Lakes will move eastward off the Northeast Coast overnight Saturday. The system will aid in producing light snow over parts of the Lower Great Lakes/Middle Mississippi Valley into parts of the Northeast, ending overnight Saturday from west to east. In the wake of the front, lake effect snow will develop over parts of the Upper Great Lakes through Saturday night. Another front sinking southward from Central Canada will move into the Northern Tier State into the Upper Great Lakes Sunday evening into Monday. Light snow will return to the parts of the Upper Great Lakes Sunday afternoon into Monday as another area of light snow develops over parts of Northern Plains Sunday evening into Monday. A third front extending from the Middle Mississippi Valley to the Southern Rockies will move eastward to the Ohio Valley/Central Appalachians by Sunday evening. Areas of rain and snow will develop over parts of the Central Plains into the Western Ohio Valley by Saturday afternoon that will move eastward into the Lower Great Lakes/Ohio Valley by Sunday afternoon. The area of rain and snow will move into parts of the Northern Mid-Atlantic/Southern New England by overnight Sunday. By Sunday afternoon the rain and snow over the Ohio Valley/Middle Mississippi Valley will turn over to all rain and continue into overnight Sunday. Furthermore, moisture moving northward out of the Western Gulf of Mexico will aid in producing showers and thunderstorms over parts of the Western Gulf Coast overnight Saturday through Sunday night. In the meantime, Arctic high pressure over the Northern High Plains will move southeastward to the Central Plains by Sunday afternoon. Upslope flow associated with the clockwise circulation around the high pressure will aid in producing snow over parts of the Central Rockies on Saturday morning ending by Saturday evening. The Arctic high will lead to temperatures nearly 25 degrees below average over the Northern/Central Plains. As the wildfires continue to burn across California, high pressure and upper-level ridging sits over the Western U.S. leading to air stagnation and air quality alerts over the region that will persist through Monday. These alerts are in effect for areas across the Pacific Northwest and Central/Southern California. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php