Unsettled weather continues across the West Sunday with some locallyheavy rainfall and isolated flood risk for Southern California andArizona...Risk for severe weather and flash flooding from the Middle MississippiValley southwestward into the Southern Plains on Monday.Showers and storms with some severe weather and flash flooding threatfor portions of the Midwest/Ohio Valley Sunday into Monday.Unsettled weather will continue across the West as a deep upper-trough andaccompanying surface frontal system push inland across the region.Widespread showers and storms will continue this evening in SouthernCalifornia but should decrease in coverage/intensity as the cold frontpushes eastward, reducing the influx of moisture. A Slight Risk ofExcessive Rainfall (level 2/4) remains in effect for the LA Basin/easternTransverse Ranges south through the Peninsular Ranges through Sundaymorning where the additional rainfall may lead to some instances offlooding given the wet antecedent conditions from the prior days'rainfall. Some more isolated instances may also continue into the daySunday before the rain fully tapers off. Additional locally heavy rainfallwith an isolated flood risk will stretch into the Lower Colorado RiverValley through Sunday morning, and into portions of southern ArizonaSunday. Otherwise, lower elevation rain showers/thunderstorms and higherelevation mountain snow are expected more broadly across the Great Basin,Southwest, and Rockies Sunday. Locally heavy snow is forecast for some ofthe regional mountain ranges, particularly from the Sierra eastwardthrough the Great Basin/Four Corners region into the central Rockies, withsome Winter Storm Warnings/Winter Weather Advisories in place. Some snowmay mix in at lower elevations in the Great Basin and into the Rockies astemperatures remain cooler following a cold front passage, though anyaccumulations should remain light. Precipiation chances should come downthrough the day Monday as the frontal system pushes eastward into thePlains.As the upper-trough shifts east, lee cyclogenesis will help tostrengthen/consolidate an area of low pressure over the Central Plainsalong a wavy, quasi-stationary boundary extending eastward through theMiddle-Mississippi Valley and into the Mid-Atlantic. This boundary willbecome the focus for areas of widespread showers and thunderstorms overthe next couple of days. The Central/Southern Plains will remain mostlydry Sunday, with precipitation limited to a wintry mix to the north of theboundary over portions of the Northern Plains in the presence of moist,upslope flow. Some light to moderate snow accumulations are expected,particularly in vicinity of the Black Hills. Then, on Monday, the focusshifts southeastward to the frontal boundary through the MiddleMississippi Valley southwestward along a dry line and approaching coldfront through the Southern Plains. Increasing moisture/buoyancy as well asstrengthening deep and low-level shear will lead to the threat of numerousthunderstorms with the potential for severe weather. The Storm PredictionCenter has outlined an Enhanced Risk (level 3/5) from central Missourisouthwestward into eastern Oklahoma where an increasing potential for verylarge hail, damaging winds, and tornadoes exists. A broader Slight Riskextends southward into north Texas. In addition, the expectation forrepeated storms with increasing coverage as flow runs parallel to theapproaching cold front has prompted an overlapping Slight Risk ofExcessive Rainfall from central Missouri southwestward into northeasternOklahoma.