Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 239 AM EST Sun Nov 03 2019 Valid 12Z Sun Nov 03 2019 - 12Z Tue Nov 05 2019 ...Air Stagnation Advisory over parts o the Pacific Northwest into the Northern Intermountain Region... A front over the Upper Midwest will become better defined on Sunday as front moves from the Upper Mississippi Valley into the Great Lakes overnight Sunday into Monday. Weak upper-level energy ahead of the front will aid in producing scattered snow showers downwind from the Great Lakes. The aforementioned front will aid in producing scattered rain and snow showers over parts of the Northern High Plains on Sunday that will move into parts of the Northern Plains by Sunday evening. Temperatures will become colder behind the front as more snow showers develop over the Northern High Plains on Sunday evening into Monday. On Monday, the front will move into the Lower Great Lakes by Monday evening. A second front will move out of Central Canada that will move into the Upper Great Lakes by Tuesday. The associated upper-level energy will aid in producing areas of snow and rain over parts of the Great Lakes on Monday. By Tuesday morning snow showers will linger over the Upper Great Lakes while rain moves into parts of the Northeast into parts of the Ohio Valley. Meanwhile, a lingering front over Southern Florida will aid in producing showers and thunderstorms over the area through Tuesday morning. Upper-level ridging and high pressure at the surface, over the Northwest, will aid in producing conditions favorable for Air Stagnation. The Air Stagnation will occur due to the sinking motion of the air under the upper-level ridge and light winds at the surface that will keep pollutants over the area. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php