Technical NOAA Weather Discussion

FXUS66 KMTR 190452
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
952 PM PDT Sat Jul 18 2026

...New AVIATION, MARINE...

.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...
(06Z TAFS)
Issued at 952 PM PDT Sat Jul 18 2026

Stratus is pushing in to the Bay Area and Central Coast with most 
sites reporting IFR ceilings. Confidence is increasing that LIFR 
CIGs will develop, at least, along the coast with some potential 
across interior sites. Confidence remains low that fog will develop 
but cannot rule out patchy fog within the North Bay valleys and 
along the coast. Conditions improve by mid to late morning with 
stratus returning early tomorrow evening. Diurnally breezy onshore 
winds continue.

Vicinity of SFO...Stratus is working its way into SFO with the site 
currently bouncing between IFR and VFR conditions. IFR conditions 
are expected to prevail for much of tonight with clearing by late 
morning. Stratus looks to return tomorrow evening but confidence is 
low to moderate on the current timing of stratus return. Diurnally 
breezy onshore winds continue.

SFO Bridge Approach...Similar to last night, stratus may take longer 
to fill in over the SF Bay/bridge approach than over the SFO 
terminal. Otherwise, similar to SFO.

Monterey Bay Terminals...IFR-LIFR overnight with some potential for 
fog during the early morning hours. CIGs have continued to lower at 
MRY which is increasing confidence that LIFR CIGs will be observed 
overnight. Model guidance supports widespread LIFR CIGs and the 
potential for reductions in visibility tonight. LIFR CIGs may make 
the chances for reduced visibility tonight higher than it was the 
previous night. Moderate confidence that stratus will clear by the 
late morning before an early evening return.&&

.MARINE...
(Tonight through next Friday)
Issued at 952 PM PDT Sat Jul 18 2026

Winds continue to decrease overnight with a moderate northwesterly
breeze to prevail into next week. Moderate seas prevail through
the forecast. 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.

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Kennedy
MARINE...Kennedy

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Prepared by Boulder-Creek.com Weather at: Sun Jul 19 00:30:03 PDT 2026
From the National Weather Service