Heavy snow over parts of the Central Appalachians/northernMid-Atlantic, PHILADELPHIA AND NYCLake-effect snow over parts of the Great Lakes and snow over thePacific Northwest to the Central Rockies and Sierra Nevada Mountains.There is a Slight Risk of excessive rainfall over parts of Californiafrom Saturday into Sunday.A wave of low pressure over the Ohio Valley will move northeastward offthe Mid-Atlantic Coast by Saturday morning. The system will create snowover the Middle Mississippi Valley/Ohio Valley and heavy snow over partsof the Central Appalachians and northern Mid-Atlantic from Friday eveninginto Saturday morning. The snow will result in reduced visibility andhazardous driving conditions. The snow will linger over parts of theCentral Appalachians/northern Mid-Atlantic through Saturday evening.Moreover, showers and thunderstorms will develop over parts of theSouthern Ohio/Tennessee/Lower Mississippi Valleys, ending on Saturday. Theshowers and thunderstorms will move into parts of the Southeast overnight,Friday through Sunday.Furthermore, upper-level energy moving over the Great Lakes into theNortheast will produce lake-effect snow downwind from the Great Lakes,with the heaviest amounts over the eastern UP of Michigan and northwesternLP of Michigan. Other areas of heavier snow will be downwind from LakesErie and Ontario. The snow will continue through Sunday. The snow willresult in reduced visibility and hazardous driving conditions. Additionally, upper-level energy over the Northern Rockies will aid increating snow over parts of the Great Basin and the Central Rockiesthrough early Saturday morning. On Saturday morning, snow will developover parts of the Central/Southern High Plains, ending by Saturdayevening. The snow will result in reduced visibility and hazardous drivingconditions.Meanwhile, a front off-shore from the West Coast will move onshore anddissipate by Saturday evening. Upper-level energy associated with thedying front moves over the Pacific Northwest, producing rain andhigher-elevation snow from early Saturday morning through Sunday. Snowwill also develop overnight Saturday into Sunday over parts of theNorthern Intermountain Region.In addition, on Saturday, rain and higher-elevation snow will develop overparts of Northern/Central California. Further, a plume of moisture willstream into California on Saturday, producing areas of heavy rain.Therefore, the WPC has issued a Slight Risk of excessive rainfall overparts of Northern California from Saturday into Sunday morning. Theassociated heavy rain will create mainly localized areas of flashflooding, with urban areas, roads, small streams, and burn scars the mostvulnerable.On Sunday, the plume of moisture will move over Southern California,producing heavy rain from Northern California to Southern California.Therefore, the WPC has issued a Slight Risk of excessive rainfall overparts of Northern California to Southern California on Sunday. Theassociated heavy rain will create mainly localized areas of flashflooding, with urban areas, roads, small streams, and burn scars the mostvulnerable.