FXUS66 KMTR 182330
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
430 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...
(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.
&&
$$
SHORT TERM...JM
LONG TERM....JM
AVIATION...Kennedy
MARINE...Bain
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Prepared by Boulder-Creek.com Weather at: Sat Jul 18 20:30:03 PDT 2026
From the National Weather Service
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