839 FXUS66 KMTR 260356 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 856 PM PDT Fri Jul 25 2025 ...New UPDATE, MARINE... .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... (00Z TAFS) Issued at 435 PM PDT Fri Jul 25 2025 Coastal MVFR-IFR stratus persists along patches on the coast, coming inland near Point Reyes, through the Golden Gate immediately north of SFO, across the western half of the San Mateo Peninsula, and into the southern Monterey Bay region. Stratus will redevelop inland this evening and overnight, with the stratus retreating to the immediate coast through Saturday morning. Low to medium probability that stratus lingers through the Golden Gate and impacts SFO and OAK through Saturday. Breezy onshore flow continues through the evening hours, diminishing overnight before returning Saturday afternoon. Vicinity of SFO... MVFR-IFR stratus hovers just to the north of the terminal and will return to the terminal area imminently. Stratus continues into Saturday, with low confidence in the clearing time and a distinct possibility that stratus will clear just to the north of the terminal. Probabilities that stratus lingers through Saturday hover around 30-40% at this time. Stratus returns to the terminal Saturday afternoon or evening. Breezy west flow continues through the evening hours, diminishing overnight before resuming Saturday afternoon. SFO Bridge Approach... Similar to SFO. Monterey Bay Terminals... Stratus has arrived at MRY and is expected to return to SNS within the next couple of hours. Generally IFR ceilings are expected 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. Breezy onshore flow persists through the evening with the winds diminishing overnight, before the 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