Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EST Tue Feb 20 2024 Valid 00Z Wed Feb 21 2024 - 00Z Fri Feb 23 2024 ...Heavy rain and heavy mountain snow in California continue through tomorrow before subsiding... ...Warming trend expected to expand from the Great Plains into the Midwest through midweek... ...Critical Fire Weather day over portions of the Southern Plains on Wednesday... The main area of unsettled weather through the next 24 hours remains over California as showers and thunderstorms stream inland associated with a deep upper-trough and atmospheric river. Southern California is once again "under the gun" for numerous instances of flash flooding as the main band of atmospheric river rainfall focuses through the overnight hours there. Given the combination of saturated soils from previous rainfall and periods of high rainfall rates approaching 1"/hour, a Moderate Risk of Excessive Rainfall is in effect for Los Angeles and northern San Diego counties through tomorrow morning. Outside of these areas, a broader Slight Risk area (level 2/4) extends from Humboldt County down to San Diego, as well as the Sacramento Valley and adjacent upslope areas of the Sierra where scattered flash flooding is possible. In the mountains, an additional 6-12 inches of snowfall are expected for the Sierra, while 12-18 inches are likely over the Shasta Siskiyous today. East of the Sierra, the influx of Eastern Pacific moisture combined with falling snow levels will support moderate to heavy snow over the Intermountain West where generally between 6-12 inches of snow can be expected. This snowfall is likely to continue into Wednesday and expand in coverage into the Central Rockies. East of the Continental Divide, widespread unseasonable warmth will prevail through the work week as all of the cold Polar air remains confined over Canada. This warm weather combined with dry, windy conditions behind a cold front and dryline supports a Critical (level 2/3) fire weather threat over portions of the Southern Plains tomorrow according to the Storm Prediction Center. By Thursday, a developing wave of low-pressure along a cold front will yield widespread showers and thunderstorms over the Ohio Valley, which could lead to isolated instances of flash flooding. Asherman/Kebede Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php