163 FXUS66 KMTR 260500 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1000 PM PDT Fri Jul 25 2025 ...New AVIATION... .KEY MESSAGES... Updated at 1211 AM PDT Fri Jul 25 2025 - Cool weather continues through Saturday - Temperatures return closer to normal starting Sunday && .UPDATE... Issued at 856 PM PDT Fri Jul 25 2025 The evening shift has been keeping eyes toward the convective environment to north and east, but only for the chance that a stray storm makes it into the CWA. The evening balloon data still shows that the Bay Area isn`t the best environment for creating and supporting convection, but could still be enough to allow a passing cell from the more convective areas to survive. The slight chances for storms lingers into the night and through Saturday morning before exiting. -Murdock && .SHORT TERM... Issued at 108 PM PDT Fri Jul 25 2025 (This evening through Saturday) Low clouds are scattering out and/or dissipating across much of the region this afternoon. However, temperatures this afternoon will remain 5-15 degrees F below seasonal averages as a cut-off low remains over the San Francisco Bay Area. With PWAT values just above 1.00" and MUCAPE values between 100-250 J/kg, there is around 5% chance of high based convection across the far northern portions of the North Bay this evening into early Saturday morning. Expecting an early return of stratus into the coastal valleys again overnight with a good likelihood for coastal drizzle and drizzle in the favored upslope regions across the area. These low clouds are then forecast to dissipate across much of the region as we head into Saturday afternoon with similar temperatures as today. && .LONG TERM... Issued at 1211 AM PDT Fri Jul 25 2025 (Saturday night through Thursday) The long wave pattern is mounting a rescue mission for the cut-off low this weekend. By Sunday an approaching trough over the East Pacific will gradually re-absorb the low. The pattern change might not be obvious at the surface as the trough will then linger near the coast, providing a similar cooling effect as the cut-off low. At the same time high pressure will build over the desert SW, bringing triple digit heat to our friends in southern Arizona. The battle between these two features will cause temperatures to rise Sunday, but still remain slightly below seasonal normals. The loss of the cut-off low will cause the marine layer to thin a bit, but don`t expect to see a sunrise anytime soon. This new pattern looks very stable, with temperatures remaining near or just below seasonal normal through next week. That`s still warmer than it`s been, however. So will a summer heat wave ever hit? There is some indication in the ECMWF ensemble mean that the SW US high and subtropical high over the central pacific will merge over northern California sometime around August 6. The GEFS mean shows similar timing. We`re talking nearly 2 weeks out, so take this with a grain of salt. In fact we had similar indications a month ago about July. Not only did that heat wave not happen, July 2025 may end up in the coldest 10% of Julys on record. && .AVIATION... (06Z TAFS) Issued at 1000 PM PDT Fri Jul 25 2025 MVFR-IFR stratus developing from the coast into the Bay Area and Central Coast, continuing to redevelop inland through the night. Stratus retreats to the immediate coast through Saturday morning with a low to medium probability that stratus lingers through the Golden Gate and impacts SFO and OAK through the day. Breezy onshore flow continues to diminish through the next few hours and returns Saturday afternoon and evening. Vicinity of SFO... MVFR-IFR stratus through Saturday, with low confidence in the clearing time and a distinct possibility that the edge of the stratus will lie just to the north of the terminal. Probabilities that stratus lingers through Saturday hover around 20- 35% at this time. Stratus returns to the terminal late Saturday afternoon or evening. Light west breezes continue through the night before breezy flow resumes Saturday afternoon. SFO Bridge Approach... Similar to SFO. Monterey Bay Terminals... IFR ceilings through the night with some LIFR possible at the coast. Stratus clears through Saturday afternoon at SNS, with moderate confidence for clearing at MRY sometime in the afternoon, before the stratus returns early in the evening. Light winds continue overnight, before onshore winds return Saturday afternoon. && .MARINE... (Tonight through next Thursday) Issued at 856 PM PDT Fri Jul 25 2025 Moderate northwest breezes and moderate seas prevail through Tuesday. Low clouds with drizzle are expected through Saturday morning. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ SHORT TERM...RGass 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