Heavy snow over parts of the Southern Plain/Middle Mississippi Valleyon Sunday and over the Northeast overnight Monday into Tuesday.There is a Slight Risk of excessive rainfall over parts of SouthernAppalachians/Southeast into the southern Mid-Atlantic.There is an Enhanced Risk of severe thunderstorms over parts of theWestern Gulf Coast/Lower Mississippi Valley on Sunday; there is a SlightRisk of severe thunderstorms over parts of the Central GulfCoast/Southeast on Monday.Low pressure, an associated front along the Gulf Coast, movesnortheastward to the Mid-Atlantic Coast by Tuesday and then moves out overthe Western Atlantic. The low will pull moisture off the Gulf of Mexico,producing an area of heavy rain over parts of the SouthernAppalachians/Southeast. Therefore, the WPC has issued a Slight Risk ofexcessive rainfall over parts of the Southern Appalachians/Southeastthrough Monday morning. The associated heavy rain will create mainlylocalized areas of flash flooding, with urban areas, roads, and smallstreams the most vulnerable.In addition, showers and severe thunderstorms will develop over parts ofthe Central Gulf Coast. Therefore, the SPC has issued an Enhanced Risk ofsevere thunderstorms over the Western Gulf Coast/Lower Mississippi Valleythrough Monday morning. The hazards associated with these thunderstormsare frequent lightning, severe thunderstorm wind gusts, hail, and a fewtornadoes. Furthermore, there is an increased threat of EF2-EF5 and hailtwo inches or greater over parts of the Western Gulf Coast/LowerMississippi Valley into Monday morning. Moreover, a narrow strip of heavysnow will develop over parts of the Southern Plains/Middle MississippiValley Sunday night into Monday morning. On Monday, the threat of excessive rainfall continues as heavy raindevelops over parts of the Southern Appalachians/southern Mid-Atlantic.Therefore, the WPC has issued a Slight Risk of excessive rainfall overparts of the Southern Appalachians/southern Mid-Atlantic from Monday intoTuesday morning. The associated heavy rain will create mainly localizedareas of flash flooding, with urban areas, roads, and small streams themost vulnerable.Similarly, the threat of severe thunderstorms continues on Monday.Therefore, the SPC has issued a Slight Risk of severe thunderstorms overparts of the Central Gulf Coast/Southeast from Monday into Tuesdaymorning. The hazards associated with these thunderstorms are frequentlightning, severe thunderstorm wind gusts, hail, and a few tornadoes.Additionally, as the low moves northeastward, light to moderate snow willdevelop over parts of the Ohio Valley. Further, heavy snow will developovernight over parts of the Northeast, Monday into Tuesday. Meanwhile, another wave of low pressure moving along a front over theUpper Midwest will produce snow over parts of the Upper Mississippi Valleyand Upper Great Lakes from Sunday into Monday. However, light snow willcontinue over the Upper Great Lakes on Tuesday.Furthermore, upper-level energy moving across the Pacific Northwest to theNorthern Plains will rain and higher elevation snow over parts of thePacific Northwest through Monday evening. As the energy moves eastward,snow develops over parts of the Northern Intermountain Region/NorthernRockies that will continue into Tuesday evening. On Tuesday, snow willdevelop over parts of the Northern Plains.