Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
363 FXUS66 KSTO 222028 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 1228 PM PST Fri Nov 22 2024 .SYNOPSIS... Day 3 of a strong Atmospheric River will continue to bring moderate to heavy rain to the area through tonight. Heavy snow is then expected over the Sierra off and on through Tuesday morning above 6000 feet. Rain chances will slowly decrease over the valley with dry conditions by early next week through Thanksgiving. *Winter Storm Warning: From 4 PM Today through 4 PM Tuesday for elevations above 6000 feet along the Sierra/ Southern Cascades including Interstate 80 and Highway 50. *Flood Watch: Through 4 AM Tonight for Valley/foothills locations generally north Interstate 80 and below 3000 feet. .DISCUSSION... The last wave of energy and moisture from the strong atmospheric river system will continue to push across the area for the remainder of the night into Saturday morning. The AR will stall out a bit over the I-80 corridor late this afternoon and evening and will likely bring some urban and small stream flooding but overall high impacts not expected. We have issued an urban and small stream advisory for these expected impacts. This main bulk of rain tonight will be further south then the first 2 days of the storm which should help with overall impacts. Also tonight as the main push of moisture moves across snow levels will be up around 7000 feet but will quickly drop down to around 5000 feet by Saturday morning. This snow will continue most of the day Saturday. At lower elevations Saturday precipitation will take a break with better chances in foothills with upslope westerly flow. There will also likely be at least some thunderstorm activity Saturday as we should get some clearing in the valley allowing things to destabilize a bit. At this time looks like main threat would remain south of Park Fire burn scar...but may have to take a closer look tonight and tomorrow for burn scar risk. Saturday night through Sunday...our Winter Storm Warning will continue but we should see a break in heavier snow. Monday...upper energy remain off shore and flow amplifies a bit to pull some higher precipitable water northward into our area yet again. Overall...this will result in an uptick in snow above 5500 once again. .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... Ensembles in good agreement that last of the upper energy will finally push across NorCal. This will result in yet another day of higher level snow in the Sierra bringing totals generally 1 to 3 feet with around 4 at highest elevations. Significant accumulations should remain above 6000 feet. Wednesday and beyond NorCal will be in a general dry northwest flow aloft which will result in dry conditions and temperatures in the mid 50s to around 60. A mild low impact Thanksgiving looks on track at this time. Rasch && .AVIATION... Moderate to locally heavy precipitation continues to move across the region resulting in periods of VFR/MVFR/IFR conditions across the Valley and foothills with areas of IFR/LIFR in the mountains. Conditions are expected to improve after 10Z Saturday and going into Saturday. Gusty southerly winds will continue, with gusts of 20 to 40 kts in the Valley and foothills, and 30 to 50 kts over the Sierra. Winds are expected to decrease for the next 24 hours but remain breezy through the day with gusts 15-30 kts in the Valley by the evening. && .STO WATCHES/WARNINGS/ADVISORIES... Flood Watch through late tonight for Central Sacramento Valley- Mountains Southwestern Shasta County to Western Colusa County- Northeast Foothills/Sacramento Valley-Northern Sacramento Valley- Shasta Lake Area / Northern Shasta County. Winter Storm Warning from 4 PM this afternoon to 4 PM PST Tuesday for West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park. && $$