Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 305 AM EST Tue Feb 06 2024 Valid 12Z Tue Feb 06 2024 - 12Z Thu Feb 08 2024 ...Heavy rain and flash flooding threat expands from Southern California into the Desert Southwest Tuesday... ...Heavy Snow for the Intermountain West mountains through mid-week... ...Temperatures will continue to run above average from the Plains to the Northeast with record breaking warmth for parts of the Upper Midwest... Showers and thunderstorms will continue to linger for Southern California while increasing across the Desert Southwest Tuesday as Pacific moisture flows northward ahead of a slow moving deep upper-level trough/surface frontal system. The anomalously high moisture as well as favorable upslope flow along the higher terrain of the Transverse and Peninsula ranges in Southern California and the Mogollon Rim in Arizona will lead to locally heavy rainfall. Slight Risks of Excessive Rainfall (level 2/4) are in effect for the threat of some scattered instances of flash flooding for both portions of Southern California and the Colorado River Basin. Although rain rates/totals will be trending downward across Southern California compared to the last couple of days, the risk for flooding and mud/debris flows remains given the very wet antecedent conditions. For higher elevations, snowfall will be coming down for the Sierra Nevada while remaining heavy for elevations above 7000 feet in the Transverse/Peninsular ranges. A continued influx of moisture from the Pacific as the upper-level trough moves slowly eastward will bring heavy snowfall to the regional mountain ranges of the Intermountain West over the next couple of days. Some particularly high totals are expected for the Four Corners region, where amounts of 2+ feet are currently forecast. Other ranges of the Great Basin and Northern Rockies will see totals generally between 6-12", with some locally higher amounts possible. Lower elevation/valley locations across the region will see a mix of moderate rain and snow showers, though any snow accumulations are expected to remain limited. Height falls beginning to overspread the Northern/Central High Plains will also lead to enhanced lee cylogenisis and a developing low pressure/frontal system Wednesday. This will bring increasing chances for wintry precipitation spreading eastward across the Northern High Plains as the system strengthens. Some freezing rain and sleet will be possible, as well as for a few inches of snow, particularly for northeastern Montana. Elsewhere, the Midwest, South, and East Coast will remain mostly dry through mid-week. Upper-level ridging over the central/eastern U.S. will also keep temperatures generally mild and above average from the Plains to the Northeast/Appalachians, with below average temperatures along the coastal Southeast and west of the Rockies. Highs across the Northern Plains/Upper Midwest in particular continue to remain upwards of 20-30 degrees above average, with 40s and 50s forecast. Some daily record-tying/breaking high temperatures will be possible for the Upper Midwest Tuesday and Wednesday. Putnam Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php