Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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573 FXUS66 KMTR 211820 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1120 AM PDT Sat Sep 21 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 315 AM PDT Sat Sep 21 2024 Gradual warming continues this afternoon, though todays highs will still be at or slightly below normal for most locations across our area. The potential for moderate HeatRisk Monday and Tuesday remains in the forecast. && .UPDATE... Issued at 845 AM PDT Sat Sep 21 2024 Stratus extends across most of the region`s valleys, mixing out through the morning inland with patchy clouds remaining at the immediate coast. Latest observations from the Fort Ord profiler suggest that the marine layer is gradually compressing as high pressure builds over the region, with the last report suggesting a marine layer around 1600 feet. A warming trend is still expected through the day, but the 24 hour trends are lagging behind. Not enough confidence to update the forecast at this time, but will continue to monitor the trends through the afternoon to see if we need to bump down temperatures for the second day in a row. DialH && .SHORT TERM... (Today and tonight) Issued at 315 AM PDT Sat Sep 21 2024 High pressure expanding across our area today and tomorrow will result in quiet weather with gradual warming today and tomorrow. Marine boundary layer (re: Ft Ord profiler) was steady at around 2k ft yesterday, with similar low level onshore flow persisting today. Low level stratus will clear farther inland by mid morning over the Bay Area and late morning around gaps and valleys around Monterey Bay. Some low stratus will linger over coastal communities this afternoon, but will see more of a mix of sun and clouds than what was realized on Friday. This will help temps near the coastline get in on the gradual warming that will occur farther inland. Tomorrow will be similar, just a few degrees warmer as H50 heights continue to slightly increase. && .LONG TERM... (Sunday through Friday) Issued at 315 AM PDT Sat Sep 21 2024 A weak upper level low begins to develop over the California Central Coast tomorrow interrupting the expanding area of high pressure to our west over open water. Deterministic guidance is in a little better agreement with the evolution of the upper level disturbance than in previous runs. The weak closed low wanders southward Monday, lifting back to the north offshore of our area on Tuesday, and then farther north to be absorbed by the Polar Jet on Wednesday. The net result appears to be less impactful heat event for Monday and Tuesday than previously thought, though moderate HeatRisk remains a possibility for many interior locations for both Monday and Tuesday. Persistent, offshore upper level troughing for the second half of next week will help cool daytime temps back to around seasonal averages for Wednesday and beyond. && .AVIATION... (18Z TAFS) Issued at 1119 AM PDT Sat Sep 21 2024 Stratus has cleared from most area terminals this morning, leaving behind VFR in its wake. VFR will persist through the early evening today with W/NW breezy winds at area terminals this afternoon. Stratus begins to return in the early portion of the evening for Monterey Bay tonight, but later for most other terminals. However, stratus is likely to bring IFR CIGs overnight for the majority of terminals. Late morning clearing to VFR on Sunday expected. Vicinity of SFO...VFR lasts through the early morning of Sunday, though confidence on this is only moderate. Some models indicate a return of stratus prior to midnight, though at this time, higher confidence is placed in stratus bringing MVFR CIGs beyond midnight for KSFO. Otherwise, breezy NW winds return this afternoon, but settle and become light into the late evening. SFO Bridge Approach...Clear through the day today. Low coastal clouds are likely to filter into the SF Bay overnight bringing low CIGs. Monterey Bay Terminals...IFR CIGs are expected to clear soon, with VFR lasting through the late afternoon today. Stratus will make an early return, bringing IFR CIGs once more towards the 00-02Z Sunday window. In the overnight, CIGs are expected to lower to become LIFR, with some reduction in visibility as fog develops. && .MARINE... (Today through Thursday) Issued at 1119 AM PDT Sat Sep 21 2024 Fresh to moderate northwest winds continue, with strong gusts over the far northern outer waters through Monday. Seas will be moderate, continuing to build and remain rough in the outer waters with significant wave heights up to 12 feet. Winds decrease and seas abate beginning Tuesday. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...JM LONG TERM....JM AVIATION...AC MARINE...AC 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