, Issued at 1200 AM PDT Mon Aug 24 2026 (Today and tonight)
For the last couple of days we've written the tale of a battle between the eastern Pacific trough and the Desert Southwest ridge that has dominated our weather pattern. Today it's the troughing that will take the upper hand as a cutoff low inches towards the Pacific Northwest, leading to slightly cooler temperatures and cloudier mornings across the region. Another interesting factor today is a weak shortwave trough coming into the region through the morning. The two main global weather models, the European ECMWF and the American GFS, are showing that there could be enough instability, moisture, and lift to maybe, just maybe, support a few high-based thunderstorms developing across the North Bay, particularly over Napa County. This is a very low probability forecast (around 5% chance through around 11 AM), along with a low confidence for storm development. The higher resolution NAM, HRRR, and RRFS models do not show any signs of developing storms, lapse rates aloft are marginal at best, and K-Index values below 20 degrees Celsius suggest no chance for developing thunderstorms. Any precipitation that does develop is also likely to end up as virga, evaporating within the vast dry low layer where relative humidity values as of the 0Z (5 PM PDT) OAK sounding fell into the single digits.
Today's highs range from the 80s into the lower 90s for the inland valleys, the middle 90s to the triple digits across the warmest interior spots, the upper 60s to the upper 70s near the Bays, and the upper 50s to the middle 60s along the Pacific coast. The higher elevations above the marine layer influence will remain rather day, especially during the afternoon and evening hours. Breezy onshore pattern winds will develop this afternoon and evening with wind gusts reaching 20 to 30 mph along coastal jet regions, through favored gaps and passes, and within the northern Salinas Valley. Smoke from the Timber Fire will continue impacting the immediate area around the actively burning fire through the day, with winds aloft lofting the smoke plume over Salinas and Hollister. For air quality information, refer to products issued by the Monterey Bay Air Resources District.
..issued at 1200 AM PDT Mon Aug 24 2026 (Tuesday through Sunday)
Temperatures rebound Tuesday and Wednesday as the ridge reasserts itself, with the inland valleys reaching highs in the middle 80s to the middle 90s on Wednesday and Thursday while the Bays reach the lower 70s to the lower 80s. A pattern change will begin later on Thursday as a deep trough builds into the West Coast while the ridge begins to inch its way eastwards towards the Southern Plains. It will be interesting to see what the trough will do as the upcoming weekend comes closer and we are better able to refine the forecast. Also worth a mention is the possibility of tropical moisture coming into the region, with our colleagues at the National Hurricane Center tracking Tropical Storm Iselle and three other areas of interest off the coast of Mexico. While the circulations remain far to the south of our waters, the resultant moisture will be captured by the developing trough with a wide variation in just how far north the moisture goes. By way of example, the deterministic European ECMWF model brings a swath of tropical moisture into the San Francisco Bay Area by Friday morning, whereas the deterministic GFS keeps the moisture plume to the south of Monterey County. In addition, wave models are also showing an increase in southerly swells as the tropical eastern Pacific remains active into the early part of next week.
(12z TAFS) Issued at 423 AM PDT Mon Aug 24 2026
Mixed bag of VFR/IFR/LIFR early this morning. Status filled north into KSTS and is expected to lift by mid morning with VFR expected to prevail across the Bay Area terminals and inland South Bay airports. IFR/LIFR ceilings over Monterey Bay will give way to VFR late morning, with IFR ceilings returning before sunset.
Vicinity of SFO, Low stratus lingers in vicinity of the terminals but not expected to impact ceilings with VFR expected to prevail throughout the day into the evening hours with MVFR/IFR expected to develop around midnight.
SFO Bridge Approach, Similar as SFO.
Monterey Bay Terminals, A relatively normal diurnal cycle of IFR/LIFR ceilings expected through the forecast period, with current IFR/LIFR ceilings expected to lift by late morning and return in the early evening hours before sunset. Expect periods of breezy onshore flow in the afternoon.
(today through Saturday) Issued at 423 AM PDT Mon Aug 24 2026
Gentle northwest breezes persist today into Tuesday with slight to moderate wind driven seas. Smoke from the Timber Fire along the Big Sur coast may limit visibility down as low as two miles at times. North-northwest winds begin to increase by the middle of the week, along with an increasing long period southerly swell by the end of the week into next weekend.
Ca, None. PZ, None.
