Swell Matrix

Area Forecast Discussion

National Weather Service San Francisco CA

552 am PDT Thu Oct 15 2026

Short Term

, Issued at 1149 PM PDT Wed Oct 14 2026 (Tonight through Friday)

Near critical fire weather conditions continue across the higher elevations, particularly the North Bay Interior Mountains, through Friday. A positively tilted upper level ridge remains over Oregon and Northern/Central California while a cut-off low lingers over Southern California. This setup promotes light to moderate offshore winds across the region with the potential for more moderate to gusty offshore winds across the higher elevations. Model guidance keeps gusts across the elevated terrain peaking between 20 to 30 mph with locally stronger gusts possible across the highest peaks (e.g. Mt. St. Helena). The GFS and HRRR are both in agreement that the SFO- WMC gradient will peak around -9 mb Thursday morning and -10 mb Thursday night into Friday. The NAM continues to be an outlier and suggests the gradient could peak around -14 mb but looking closer into their forecast wind gusts still keeps gusts in a similar, but slightly stronger range, of 25 to 35 mph. Very dry conditions are expected across the higher elevations during both the daytime and overnight hours. Much of the region will see daytime RH in the 10s to 20s with poor to very poor overnight recoveries with the worst recoveries across the higher elevations. Given the very dry conditions and potential for offshore winds, any spark has the potential to start a fire. Remember, one less spark one less wildfire.

Warmer temperatures continue Thursday and Friday with highs in the 80s to low 90s on Thursday and upper 80s to 90s on Friday. Patchy Moderate HeatRisk is expected on Thursday but becomes more widespread across urban areas on Friday. If you are outdoors during peak heating, make sure you are drinking plenty of water and taking frequent breaks in the shade. The marine layer remains mixed out through the short term due to the presence of the ridge so expect

Long Term

..issued at 1149 PM PDT Wed Oct 14 2026 (Friday night through next Wednesday)

Offshore winds decrease by Friday afternoon/evening as upper level ridging weakens and broad troughing returns to the region. High temperatures Saturday will still be warm in the 80s to low 90s but cooler temperatures return Sunday into next week. By Sunday, broad troughing returns to the region with temperatures cooling into the 70s to low 80s. Fall weather returns in force next week as we get our first potential rainmaker of the season. This low pressure system looks to originate from the Gulf of Alaska and will bring much cooler, moister air into the region as the surface low weakens and moves into California next week. Highs will be seasonal to below normal in the 60s to low 70s across the interior and upper 50s to low 60s along the coast. Rain chances increase Tuesday through late week with wetting rains (>0.10") likely across the Central Coast and potentially Santa Cruz County/the South Bay. Light rain is possible across the rest of the Bay Area but does not look to meet wetting rain criteria at this time. Guidance is showing a low (<10%) chance of thunderstorms next week so that will be

Aviation

(06z TAFS) Issued at 959 PM PDT Wed Oct 14 2026

Generally VFR conditions prevail through the TAF period, with some high resolution models depicting patchy coastal stratus developing tonight. Low confidence in HAF getting fog and low stratus. If it does happen, the most likely period for development would be 08-11Z before offshore winds mix out the lower layers. Light winds persist overnight, before a moderate offshore push in the interior Thursday morning, balanced by a gentle onshore flow developing in the afternoon.

Vicinity of SFO, VFR at the terminal through the TAF period. Light winds overnight will turn offshore Thursday morning before moderate northwest flow resumes in the afternoon.

SFO Bridge Approach, Similar to SFO.

Monterey Bay Terminals, VFR through the TAF period. Light to gentle offshore winds persist overnight into Thursday morning before the moderate northwest flow resumes afternoon.

(12Z TAFS) Issued at 547 AM PDT Thu Oct 15 2026

Satellite imagery shows mainly clear skies across the region. There are a few ribbons of stratus along the North Bay coastline, while the patch that was near the San Francisco Peninsula is falling apart. Look for VFR conditions at the terminals through the TAF cycle and offshore winds this morning and yet again tonight.

Vicinity of SFO, Onshore flow is expected for a few more hours which will be followed by a stint of weak offshore winds. By the early afternoon, onshore winds of 10-15kt return and then decrease after sunset. Offshore winds are expected Thursday morning. VFR conditions are expected during the TAF cycle.

SFO Bridge Approach, Similar to SFO.

Monterey Bay Terminals, Offshore winds are expected for through the morning with onshore winds by late morning or early afternoon. Onshore flow should continue through the evening, before another round of offshore winds returns late evening and into early Friday morning. VFR conditions will prevail.

Marine

(today through Tuesday) Issued at 243 AM PDT Thu Oct 15 2026

Moderate seas continue across the outer waters, while the inner waters see slight to moderate seas through Friday. During this time frame, gentle to fresh northerly breezes continue. Moderate to fresh northerly winds return for the weekend, which will be accompanied with rough seas.

Watches, Warnings, Advisories

Ca, Fire Weather Watch from this evening through Friday morning for CAZ504.

PZ, None.

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