textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 120 PM PDT Sat Jul 18 2026

- Near or slightly below normal temperatures and higher humidity through the first half of the upcoming week.

- The marine layer and mid to upper level cloud cover will continue to help keep temperatures cooler under building high pressure.

SHORT TERM

Issued at 120 PM PDT Sat Jul 18 2026 (This evening through Sunday night)

Stratus retreated back to the immediate coastline by late this morning. A few spots from Pacifica south to Monterey may only see partial clearing through mid-afternoon. A slightly stronger marine layer (~1500-2000ft) across the North Bay valleys has temperatures running 5-10 degrees cooler than this time yesterday, so have adjusted todays highs there about 3-5 degrees cooler from the NBM. The onset of a relatively normal diurnal intrusion of the marine layer this evening will occur with a similarly normal exit Sunday morning. Patchy coastal and valley fog is most likely across the North Bay with little to no impacts expected. A weak fetch of offshore flow/thermal belting at 925MB will keep overnight lows at higher elevations over the East Bay Hills and Santa Lucias well above normal with poor overnight RH recovery. Light winds will help mitigate fire weather concerns somewhat, but any ignition could spread quickly on steep slopes.

LONG TERM

Issued at 120 PM PDT Sat Jul 18 2026 (Monday through next Friday)

Temperatures will be near or below normal through the extended forecast with Tuesday being the warmest day of the week despite building high pressure. The marine layer influence, especially for the Bay Area and North Bay, will help to keep temperatures close to or below normal. Not much change to the expected push of monsoonal/tropical moisture from the south as Elida tracks north after becoming extratropical. PWATS near 2.0" and 150%-200% of normal are expected to peak Tuesday afternoon. Attm slight H50 height rises and anemic mid-level lapse rates less than 7C/km indicate a low probability of elevated convection (and dry lightning potential) developing. However, mid-level cloud cover spreading east from the remnants of Elida over the EPAC will further help to keep temperatures in check for the first half of the week, including Tuesday.

AVIATION

(00Z TAFS) Issued at 416 PM PDT Sat Jul 18 2026

VFR with widespread stratus and MVFR-IFR CIGs to return later this evening. A substantial stratus bank is located just offshore with overcast conditions to return to coastal areas shortly. An early return of stratus is expected across the interior this evening with stratus returning between 03-06Z. Moderate confidence in stratus cover dissipating between 18-20Z. Highest confidence in MVFR-IFR CIGs tonight with models again showing potential for LIFR CIGs. Confidence is low that LIFR CIGs will develop given a marine layer depth between 1000-2000 ft. Breezy afternoon/evening conditions are expected today and again tomorrow.

Vicinity of SFO...VFR with an early return of stratus this evening around 04Z. Highest confidence in MVFR CIGs with a lower chance of IFR CIGs overnight. Stratus will recede by mid to late morning with clearing expected around 17-18Z. Breezy onshore afternoon/evening winds continue today and return again tomorrow.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus is expected to move into MRY and SNS in the next 1-2 hours. Highest confidence if IFR CIGs but there is a low potential for LIFR CIGs and fog to develop during the early morning hours. Confidence is low in that scenario given the relatively deep marine layer. Conditions improve late morning/early afternoon with clearing between 18-20Z. Breezy onshore afternoon/evening winds continue today and return again tomorrow.

MARINE

(Tonight through next Thursday) Issued at 416 PM PDT Sat Jul 18 2026

Moderate to fresh northwesterly breezes will prevail over the weekend, diminishing to moderate by next week. Moderate seas will also prevail. Moderate southerly swell will increase from tropical cyclone activity across the eastern Pacific through next week.

FIRE WEATHER

Issued at 120 PM PDT Sat Jul 18 2026

Cooler than normal temperatures with assistance from onshore flow and relatively normal diurnal intrusion of the marine layer will continue through the weekend into next week. RH recovery will be excellent for coastal areas and valleys, and moderate to good farther inland. However weak offshore flow/thermal belting will result in poor RH for higher elevations, especially above 1500- 2000ft across the East Bay Hills and Santa Lucias.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 3 AM PDT Sunday for Pt Arena to Pt Reyes 10-60 NM.