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Flood Potential Outlook
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
006 FGUS76 KMTR 110031 ESFMTR CAZ006-502-505-506-508-509-512-516-517-528>530-111900- HYDROLOGIC OUTLOOK NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 431 PM PST Mon Feb 10 2025 ...AN ATMOSPHERIC RIVER TAKING AIM AT THE NORTHERN AND CENTRAL CALIFORNIA COAST WILL INCREASE THE POTENTIAL OF FLOODING TO AREA CREEKS AND STREAMS... * WHAT...Unsettled weather is forecast to return to the region this week. The first round of rain is progged to impact areas mainly south of the Golden Gate Tuesday night into Wednesday. Rainfall amounts will range from 0.10"-0.25" over inland and valley locations to 0.25"-0.75" along the coastal mountain ranges. Highest precipitation is forecast over the Santa Cruz Mountains and Santa Lucia range. A stronger and significantly wetter system will move into the area Wednesday night into Thursday. Models agree that this system will pack a bigger punch with strong upper level jet support and ample moisture associated with an atmospheric river that is taking aim at the Central Coast. This storm will not only bring heavy rainfall but also potentially damaging winds. Given the current location of the moisture axis and dynamic features, this system will generally favor areas from about San Francisco southward across the Central Coast. Overall good news in terms of annual rainfall since southern areas are a bit behind the curve so far this water year (since Oct 1). An interesting tidbit to include; the Central Coast watershed which runs along the coast roughly from Monterey to Arroyo Grande is about 4.37" below normal for the water year to date. The current forecast for that watershed by the end of the week is about 3"-6". There is a slight chance (at least 15%) of rainfall rates resulting in flash flooding conditions area-wide on Thursday. It is likely that there will be more of a focus as the event nears and more information about convective rainfall rates becomes clear from high res guidance. The system does appear to be rather progressive and should move through the region relatively quickly, thus hindering any increase in the probability of flash flooding for now. Guidance keeps this vigorous wave open and embedded in the flow, so there is relatively low stall potential. As far as rainfall totals go, the North Bay will still see respectable totals in the 2"-4" range, the greater Bay Area will see a range of 1.5"-3" (less in the rainshadowed South Bay, more along the peninsula), 4"-6" and locally up to 8" in the Santa Cruz Mtns, 2"-3" across the Central Coast counties, and 3"-6" along the Big Sur Coast, locally up to 8". * WHERE...Bay Area and Central Coast. Latest model guidance suggests the Bay Area and Central Coast will receive the greatest accumulation of precipitation with the heaviest rainfall expected over the Santa Cruz Mountains and Santa Lucia range. * WHEN...Tuesday night through Thursday. Light to locally moderate rainfall expected Tuesday night into Wednesday. Moderate to locally heavy rain expected Wednesday night into Thursday. * ADDITIONAL DETAILS...In addition to the moderate rainfall and localized ponding of water in low-lying or poorly drained areas, such as freeway offramps. Locally strong and gusty winds may result in downed trees, and potential power outages. Confidence is high that we will receive rainfall from these systems however, confidence is moderate with respect to the exact location and timing of the most intense rainfall. Details regarding this storm will likely change as the system nears. Therefore, stay tuned to the latest forecast for the most up to date weather information. $$ Behringer/CW