Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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948 FXUS66 KMTR 240000 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 400 PM PST Sat Nov 23 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 1144 AM PST Sat Nov 23 2024 Scattered showers will continue through Sunday before a cold front brings heavier precipitation to the Central Coast Monday through Tuesday. && .SHORT TERM... (This afternoon through Sunday) Issued at 1144 AM PST Sat Nov 23 2024 The cold front has moved into southern California, leaving behind a much drier, colder airmass. The precipitable water has dropped from 1.08" to 0.64" and the 850 mb temp has dropped from 7.35C to 4.35C from 12Z yesterday to 12Z today. The short term convection forecast is a bit of a mixed bag. As the sun peaks through and allows the surface to warm, instability will rise. On the other had, overall forcing is waning as a short wave trough moves toward the Sierra. With mid-level lapse rates below 5 C/km and a freezing level around 7,600 ft, any convection that forms will be weak and shallow. Thunderstorms are very unlikely this afternoon. Minor flooding impacts are still possible, but will require steady training showers, as we saw over the East Bay in the late morning. && .LONG TERM... (Sunday night through next Friday) Issued at 1144 AM PST Sat Nov 23 2024 A weaker trough will quickly move through Sunday, keeping light rain chances in the forecast and bringing a brief pulse of stronger southerly winds. Beyond Sunday, there is a lot of uncertainty regarding the precipitation this week. A weak low pressure system is likely to form just offshore somewhere between Monterey Bay and San Francisco Bay. This low will generate a cold front and SE winds will draw in moisture and moderate rain to the warm sector. Where exactly this boundary sets up will have a great influence on where the heaviest rain ends up. Our current forecast keeps the heaviest rain over the Central Coast, but that`s far from a guarantee. The ECMWF ensemble members show anywhere from 0.25" to 2.0" at SFO, for example. Coastal mountains may see up to 3 or 4 inches, but it`s unclear if that will be the Santa Cruz mountains or the Santa Lucias. Regardless of where exactly this system sets up, it will move south and allow northerly flow to return by late Tuesday or Wednesday. The dry weather should hold through Thanksgiving as a ridge begins to build over the Eastern Pacific. && .AVIATION... (00Z TAFS) Issued at 400 PM PST Sat Nov 23 2024 The heavier showers have subsided allowing for predominately VFR conditions. Some areas are still seeing some MVFR as some light occasional showers move over the terminal but most lower stratus is scattered. VFR expected to prevail through the remainder of the TAF period for most terminals but KSTS may see LIFR conditions around 12Z with VFR returning near 18Z, but confidence is low as models show VFR through the TAF period as well. Winds will be relatively moderate with moments of westerly winds going into the evening, then south/southwest winds overnight into the morning. Vicinity of SFO...VFR with a few low stratus over the airport. Winds have diminish to moderate to slightly breezy with a westerly direction. Winds diminish overnight but southerly winds will rebuild by late Sunday morning, accompanied by some light showers. Timing of showers is a bit uncertain but expect late morning early afternoon. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR through the TAF period. Westerly winds will turn southerly by early Sunday morning light vicinity showers start to move closer to the terminal. && .MARINE... (Tonight through next Friday) Issued at 400 PM PST Sat Nov 23 2024 Winds and wave heights continue to decrease with occasional scattered showers moving through the waters. Seas and winds rebuild late tonight into early next week as another storm approaches the region. Winds will initially be strongest north of Point Reyes. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 3 AM to 3 PM PST Sunday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Flynn LONG TERM....Flynn AVIATION...SO MARINE...SO Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea