Swell Matrix

Area Forecast Discussion

National Weather Service San Francisco CA

414 pm PDT Fri aug 14 2026

Short Term

, Issued at 156 PM PDT Fri Aug 14 2026 (This evening through Saturday night)

Improving sky conditions will persist this afternoon as daytime heating and mixing gradually erodes the marine stratus from east to west. A couple of persistent eddies across Bodega Bay will continue to send a feed of stratus into the North Bay. Confidence still remains high that clearing will continue here and we'll see the MaxT forecast remain on track. Winds continue to climb across some of the favored regions of the East Bay and gusts to near 40 mph are probable here. Fuels across this area are dry and there does remain some fire growth potential here (pending an ignition).

Broad troughing aloft in tandem with the SFO-SAC/SFO-SMK gradients increasing to around 3mb should spell a return of marine stratus across most of the area, with the exception being some elevations above 3000 feet. While overnight humidity recovery into Saturday will again climb above 60% for many locales, some of the peaks across the Santa Lucia and Diablo Ranges, as well as the Santa Cruz Mountains, East Bay Hills and North Bay Mountains may only experience max RH around 40%. This will hopefully help at least modulate any ongoing fire activity along the Central Coast during the overnight hours, outside of the highest peaks.

The aforementioned troughing in place will instigate orographic ascent along the coast and coastal ranges late tonight and into the pre-dawn hours on Saturday. Forecast soundings show a moist planetary boundary layer along with steep low level lapse rates capped by a nearly 20C temperature inversion. This should promote pockets of drizzle which may translate to slick road conditions and reduced visibility through about 18 UTC on Saturday. Be sure to exercise caution if commuting.

Saturday will start out gloomy and while troughing will persist, the amplitude of the wave appears a little less than today (Friday). This should translate to an earlier clearing time and a potential for greater insolation and thus warmer conditions. Temperatures will still be running a good 5 to 15 degrees below normal across the area, but it'll be a largely pleasant day.

Long Term

..issued at 156 PM PDT Fri Aug 14 2026 (Sunday through next Thursday)

As we progress into the latter half of the weekend and into next week, we'll maintain generally southwesterly flow aloft. While the onshore flow will remain in place, the trough axis will be displaced father west which may equate to less in the way of synoptic scale ascent across our area. While I cannot completely discount the potential for patchy drizzle, I'll forgo mentioning DZ Sunday and onward at this time. The marine layer may not be quite as deep at times next week and in fact, the deterministic guidance suggest a return to poor overnight humidity recovery (max RH between 20% and 40%) across the higher terrain of the Santa Lucia and Diablo Ranges as well as the East Bay/Santa Clara Hills and portions of the North Bay Mountains. Fortunately, there doesn't appear to be a strong signal for winds (outside of the favored gaps and passes), though favorable alignment of fuels (which still remain dry) and terrain could support some fire growth potential.

While the trough axis will remain a bit farther to the west, enough southwesterly flow should keep the Pacific Southwest ridge in check. While the multi-model ensemble mean keeps the heart of the ridge anchored across southern New Mexico and adjacent portions of west Texas, there are some solutions which place the ridge axis closer to the Four Corners. Should this solution verify, compression of the marine layer could mean that the current MaxT forecast toward the end of the long term period will need to be adjusted upward.

Aviation

(00z TAFS) Issued at 414 PM PDT Fri Aug 14 2026

Generally MVFR stratus persists across the coastal regions with a plume continuing to flow through the Golden Gate. Moderate and gusty onshore winds will continue into the evening hours, when winds become light and the stratus will begin expanding over all of the interior terminals. Stratus will clear out across the inland terminals late Saturday morning into the early afternoon, with breezy onshore winds resuming in the afternoon. Beyond the TAF period, a building thermal ridge will likely compress the marine layer.

Vicinity of SFO, Clouds flowing over the San Bruno Gap will likely result in pulses of MVFR ceilings at the terminal. Otherwise conditions remain generally VFR with moderate and gusty west winds through the evening hours. MVFR stratus will develop late this evening, with clearing expected sometime during the late morning or early afternoon hours on Saturday. Confidence in the clearing time is low at this time. Breezy west-northwest winds will resume Saturday afternoon, with moderate confidence in stratus returning in the evening a couple of hours before the end of the TAf period.

SFO Bridge Approach, Similar to SFO.

Monterey Bay Terminals, VFR through the next few hours before MVFR ceilings return to the terminals in the evening hours. Northwest winds will remain moderate and breezy through the evening, becoming light overnight before resuming Saturday afternoon. Stratus will clear out from SNS late on Saturday morning while moderate confidence that MRY remains socked in through the TAF period.

Marine

(tonight through next Wednesday) Issued at 414 PM PDT Fri Aug 14 2026

Gentle to moderate northwest winds will continue through early next week. Seas will continue to subside and become moderate in response. A long period southerly swell of about 16 to 18 seconds approaches the coast tonight into Sunday. Winds will freshen early to mid next week, causing seas to build up to 9 feet.

Watches, Warnings, Advisories

Ca, None. PZ, None.

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