Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 258 PM EST Fri Nov 19 2021 Valid 00Z Sat Nov 20 2021 - 00Z Mon Nov 22 2021 ...Snow showers for the Northern/Central Rockies through Saturday evening... ...Persistent onshore flow will produce showers and thunderstorms over the southern third of Florida with a marginal threat for excessive rainfall... ...Snow for Upper Great Lakes and rain from the Lower Great Lakes to the Southern Plains/Western Gulf Coast by Sunday evening... A cold dome of high pressure over the Central Appalachians will slowly begin to move off the Northeast Coast on Saturday as warmer air moves northward over the Southern Plains into the Great Lakes ahead of the next front. Meanwhile, a front over the Northern Rockies into the Great Basin moves eastward and strengthens as cold air from Central Canada moves southward over the Northern Plains on Saturday morning. Upper-level energy associated with the system will aid in producing scattered snow showers over parts of the Northern/Central Rockies through Saturday evening. Also, on Saturday, moisture from the Western Gulf of Mexico will start to moisten the air over the Lower/Middle Mississippi and Ohio Valleys. By Saturday evening, the front will be draped from the Upper Great Lakes southwestward to the Southern High Plains, moving eastward to the Great Lakes to the Western Gulf Coast as additional cold air moves southward out of Canada. On Sunday morning, rain will develop over parts of the Ohio and Mississippi Valleys, expanding into the Lower Great Lakes/Northeast and the Southern High Plains by Sunday evening. On Sunday morning, as some of the moisture wraps around the associated surface low over the Great Lakes, snow will develop over parts of the Upper Great Lakes, continuing into Sunday evening. Farther south, persistent onshore flow will stream moisture into Florida, producing showers and thunderstorms through Sunday. The associated rain will create localized areas of flash flooding, affecting areas that experience rapid runoff with heavy rain expected through Sunday morning. Therefore, the WPC has issued a Marginal Risk of excessive rainfall over parts of southeastern Florida through Sunday morning. Ziegenfelder Graphics are available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php