textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1200 AM PDT Wed May 13 2026

- Cooling trend continues today

- Warming and drying trend resumes Thursday through the weekend

SHORT TERM

Issued at 1204 AM PDT Wed May 13 2026 (Today and tonight)

A disjointed marine layer is trying to reform overnight per satellite fog product. Where it is reforming it's rather deep at 1500-2000 ft. The complicating factor in development of the marine layer is the passing upper low well to the north in OR and a trailing vort max/shortwave trough passing over region. Lastest guidance continues to advertise some expansion of the marine layer through sunrise, but it never completely fills in the "standard" marine layer footprint. Morning low clouds will give way to afternoon sunshine, even the coastal locations. The coastal clearing today will be enhanced by the increasing northerly gradients and stronger winds. SFO-ACV will ramp up to over 5 mb, which is decent. Winds will be strongest over the coastal waters this afternoon and immediate coastline with gusts of 25-45 mph possible. Despite some sunshine temperatures will be close to or below normal for mid May with highs in the 60s to lower 70s coast/bays and 70s to mid 80s inland. It will be the coldest day of the next seven.

For tonight, not expecting a ton of marine stratus due to lingering stronger northerly flow and a departing upper level trough.

LONG TERM

Issued at 1204 AM PDT Wed May 13 2026 (Thursday through Tuesday)

By Thursday zonal flow develops over the region as high pressure begins to build, but is tampered by a trough near the Gulf of AK. The semi-zonal flow will continue through Friday. As such, a gradual warming and drying trend will develop. A blip in the longwave pattern with a sagging upper level trough over CA on Saturday will drop temperatures back to near or below seasonal averages. The sagging trough deepens and develops a low that sweeps into the Great Basin. Why is this important for our area? Pattern recognition points to bursts of offshore flow over the higher terrain each night into morning hours beginning Sunday into next week. This will lead to marginal humidity recovery at night. Not a big fire concern at this point, but something we'll need to monitor over the next few days. ERC charts are catching on with a trend line back toward daily maxes.

More uncertainty for next week is around max temps Mon/Tue. While the longwave pattern shows troughing to the east and a ridge over the EPac it doesn't scream heat. The NBM is showing some rather warm temps with interior 90s again. Call it recency bias, but 850 mb not 20C+ gives me pause on max temps from the NBM. Other ens guidance is on the colder side and did verify better during our most recent warm spell. That being said, we'll need to watch this as well and trend temps down if needed. Stay tuned...

AVIATION

(06Z TAFS) Issued at 1107 PM PDT Tue May 12 2026

Breezy to gusty onshore winds will persist through a majority the TAF period for sites along the coast. Winds are reducing into the night, but are expected increase again late morning into the afternoon on Wednesday. MVFR cigs continue to develop and persisting through late morning Wednesday. The timing and coverage of IFR/LIFR cigs is low confidence, and if reached may not persist for long.

Vicinity of SFO...MVFR cigs are expected persist through late morning Wednesday. Gusty onshore winds extending through much the TAF period, peaking around 30 kts Wednesday afternoon, but winds ease Wednesday night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...MVFR cigs are expected to persist through the late night, becoming IFR after and continuing through mid-morning Wednesday. KSNS is expected to clear out Noon with some partial clearing possible at KMRY by early afternoon.

MARINE

(Tonight through next Sunday) Issued at 443 PM PDT Tue May 12 2026

Hazardous marine conditions develop midweek and will continue into next week. Winds increase through the remainder of the week with strong to near gale force winds and occasional gale force gusts Wednesday and Thursday. Wind driven seas will build to between 10 to 12 feet Wednesday and Thursday. Surface high pressure will then strengthen over the eastern Pacific Friday into next week. This will result in a strong coastal jet, widespread gale force to potentially severe gale winds, and very high, wind driven seas between 12 to 17 feet expected.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory from 9 AM this morning to 9 PM PDT this evening for Mry Bay.

Small Craft Advisory until 3 PM PDT Thursday for Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory from 9 AM this morning to 3 PM PDT Thursday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10- 60 NM-Pt Arena to Pt Reyes 10-60 NM.

Small Craft Advisory until 3 PM PDT Thursday for Pt Pinos to Pt Piedras Blancas 0-10 nm.