FXUS66 KMTR 182351
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
451 PM PDT Sat Apr 18 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1201 PM PDT Sat Apr 18 2026

 - Seasonably warm temperatures expected through the remainder of
   the weekend

 - Cooler temperatures and beneficial rain for the beginning of 
   the upcoming week

&&

.SHORT TERM...
Issued at 1201 PM PDT Sat Apr 18 2026
(This evening through Sunday)

High clouds continue to stream in from the west, yet will have very 
little impact on high temperatures this afternoon. We are 
forecasting mid 60s to lower 70s in the northwest facing locations 
and low-to-upper 70s elsewhere. There is a greater than 50% 
probability for Concord, San Jose, Gilroy, Hollister, and King City 
to exceed 80 degrees F on this afternoon (but less than 10% of 
exceeding 85 degrees F).

Tonight and into Sunday morning, expecting low clouds to return to 
the coast and coastal adjacent valleys as moisture increases ahead 
of an approaching mid/upper level low. This low will also cool 
temperatures slightly as clouds increase, most notability in the 
North Bay and San Francisco Bay Area. Meanwhile, the Central Coast 
will remain quite warm across the interior Sunday afternoon. 

&&

.LONG TERM...
Issued at 1201 PM PDT Sat Apr 18 2026
(Sunday night through next Friday)

The progression of the anticipated cold front has slowed down by 
about 12-18 hours. However, we still expect pre-frontal rain showers 
to begin Monday morning across the North Bay and then spread 
southward across the Bay Area. Outside of the coastal ranges of the 
Central Coast, we may see very little rainfall on during the day 
Monday. The main cold front is now expected to move across the Bay 
Area and Central Coast on Tuesday morning. By Tuesday afternoon and 
evening, we have the greatest potential for thunderstorms with up to 
30% across much of the region as up to 500 J/kg of surface based 
CAPE is forecast. We are mostly forecasting this rainfall to be 
beneficial, but urban and poorly drained areas may experience 
flooding concerns during periods of heavy rain showers and/or 
thunderstorms. The WPC has a Marginal Risk of Excessive Rainfall (at 
least 5%) from the Santa Cruz Mountains northward on Day 3 (5 AM 
Monday - 5 AM Tuesday). However, we are not expecting any major 
river flooding with this event. 

Post-frontal rain showers and possible thunderstorms (generally less 
than 15%) linger into Wednesday afternoon as a colder air mass 
settles in behind the cold front. Drier conditions look to return to 
the region for the latter half of the week with troughing forecast 
by the clusters. 

&&

.AVIATION...
(00Z TAFS)
Issued at 437 PM PDT Sat Apr 18 2026

High clouds continue to build across the region ahead of a cold
front over the Eastern Pacific. This front will slide very slowly
towards the coast over then next couple days, keeping a steady
supply of high level clouds in the TAFs. There is a chance for
marine layer stratus to creep in over a few terminals tonight, 
but impacts should be limited to coastal terminals. The biggest
question is STS, where model guidance is hinting at stratus
potential Sunday morning, but the dew pint is in the low 30s and
high clouds will limit nocturnal cooling, so the set-up doesn't
seem right and the confidence is quite low.

Vicinity of SFO...Moderate onshore winds are gradually weakening
this afternoon and that trend will continue through the evening.
There is a slight (20%) chance of MVFR ceilings Sunday morning
with the best chance between 12Z and 17Z.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...With higher low-level moisture, the
southern terminals have the best chance for MVFR or high IRF
ceilings tonight. MRY and SNS both have a 60% chance of these
morning clouds before the skies clear around 18Z.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 437 PM PDT Sat Apr 18 2026

Expect light winds and seas to continue through the rest of the
weekend. Northerly winds shift and become southerly Sunday ahead
of an incoming low pressure system and cold front. Winds will
strengthen ahead of the cold front Monday through Tuesday with
localized strong gusts expected. Expect moderate seas, rain and a
slight chance to chance of thunderstorms Monday night and Tuesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Flynn
MARINE...Murdock

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Prepared by Boulder-Creek.com Weather at: Sat Apr 18 20:30:02 PDT 2026