374 FXUS66 KMTR 270855 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 155 AM PDT Sun Jul 27 2025 ...New SHORT TERM, LONG TERM... .KEY MESSAGES... Updated at 1209 AM PDT Sun Jul 27 2025 - Temperatures warm slightly while remaining below seasonal normal through the week. - Strong onshore afternoon winds will gradually increase through mid-week. && .SHORT TERM... Issued at 1209 AM PDT Sun Jul 27 2025 (Today and tonight) The marine layer has compressed to around 1,600 feet according to the 00Z sounding, although the Ft. Ord profiler has indicated some expansion since then. The current stratus deck is fairly similar to 24 hours ago, with slightly less inland extent. The cloud ceilings are generally below 1,000 feet and falling, which could help bring another round of early morning drizzle to the typical locations. The basic 500 mb pattern is troughing offshore, extending from low pressure in the Gulf of Alaska, and high pressure over the Gulf States. California is centered between these two synoptic features. The high pressure will nudge the trough a little today. This will cause the 850 mb temperature to rise and max temperatures are expected to climb anywhere from 2-5 degrees compared to yesterday. Otherwise it will be pretty similar with morning clouds, a clear breezy afternoon, and clouds returning in the evening. Despite the modest warming, we are still expected to stay below the seasonal normal. && .LONG TERM... Issued at 1209 AM PDT Sun Jul 27 2025 (Monday through Saturday) The pattern described above is pretty stable, though there is a gradual long term trend. The Gulf of Alaska is a well known storm graveyard, and the 500 mb low there will gradually fill over the next several days. Meanwhile the subtropical high over the Gulf States will gain strength and push west. This feature will eventually extend a ridge from Texas to eastern Washington. At the surface this evolution will lead to a gradual increase in the N-S pressure gradient between subtropical high pressure offshore and a thermal low over Arizona. The Eureka to Santa Barbra gradient is currently around 1 mb and will reach 6 or 7 mb by mid week. Meanwhile the E-W gradient will remain fairly steady. The SFO-SAC and SFO-WMC gradients remain positive and diurnally driven according to a confident 2 km WRF ensemble. All these means that winds will remain onshore (good for fire weather) while the strength increases through the next several days. The 850 mb temperature will also gradually increase from around the 25th percentile today to around 75th percentile by Wednesday. This will translate to a very slight warming trend, however the onshore wind will be the primary driver, and keep most areas slightly cooler than normal. Higher elevations will feel the warmer and drier air mass, however. Regarding fire weather, all regions are enjoying fuel moisture well above normal, but the forecast is for the trend to reverse starting Monday, especially above the marine layer. && .AVIATION... (06Z TAFS) Issued at 958 PM PDT Sat Jul 26 2025 MVFR-IFR stratus expands from the coast into the Bay Area valleys and the Monterey Bay region. Stratus will mix out across the inland regions through Sunday morning and early afternoon while the coastal areas remain socked in. Breezy onshore winds continue to diminish over the next few hours, becoming light through Sunday morning before resuming in the afternoon. Sunday evening, expect some inland stratus to return although gradual compression of the marine layer might limit the inland extent of the ceilings. Vicinity of SFO... MVFR-IFR stratus through Sunday morning. Stratus dissipates early Sunday afternoon, with the terminal remaining VFR for a brief period before getting socked in again during the late afternoon and early evening hours. Even then, expect the stratus deck to lurk just to the north of the terminal. Breezy and gusty west winds continue to diminish through the next few hours, becoming light through Sunday morning before resuming in the afternoon. SFO Bridge Approach... Similar to SFO. Monterey Bay Terminals... MVFR-IFR through Sunday morning, with the inland regions clearing out by the early afternoon. Low probability (20-30%) that MRY remains socked in through the day, but model output currently shows a brief period of clear skies in the afternoon hours. Stratus returns in the early evening. Light winds continue overnight before breezy onshore flow returns Sunday afternoon. && .MARINE... (Tonight through next Friday) Issued at 807 PM PDT Sat Jul 26 2025 High pressure maintains northerly flow over the coastal waters through the next week. Winds will increase locally on Sunday afternoon north of Point Reyes and south of Point Sur. Moderate seas prevail through the weekend then gradually increase beginning Monday. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Monday for Pt Pinos to Pt Piedras Blancas 0-10 nm. && $$ SHORT TERM...Flynn LONG TERM....Flynn AVIATION...DialH MARINE...DialH Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea