FXUS66 KMTR 230401
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
901 PM PDT Fri May 22 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1250 PM PDT Fri May 22 2026

 - Diurnally driven onshore winds during the afternoon and early 
   evening through early next week

 - Gradual cooling trend continues with seasonal temperatures for
   the upcoming weekend and cooler temperatures early next week

&&

.UPDATE...
Issued at 658 PM PDT Fri May 22 2026

Coastal stratus is beginning to flow into the inland regions this
evening, particularly through the Petaluma Gap, Golden Gate, and
across the Monterey Bay region. The latest readings from the
Bodega Bay profiler suggest that the marine layer has further
thickened to around 2000 feet. If this holds overnight, the higher
elevations and perhaps the very eastern sections of Contra Costa 
County will be the only regions to escape stratus cover tonight.

DialH

&&

.SHORT TERM...
Issued at 1250 PM PDT Fri May 22 2026
(This evening through Saturday)

The marine layer deepen to ~1500 ft this morning and resulted in 
cooler conditions along the coast and adjacent valleys. May not have 
lowered temperature in these areas enough, however they are on a 
warming trend now the sun is out. Thus, expecting afternoon 
temperatures to warm into the upper 70s to middle 80s across the 
interior, lower 60s to lower 70s around the San Francisco bayshore, 
and upper 50s to middle 60s near the coast. Dry conditions persist 
this afternoon with elevations above 1500 ft are seeing 10%-30% 
humidity values.

As the marine layer is forecast to remain steady, low clouds near 
the coast will spread further inland this evening and spread deeper 
into the valleys early Saturday morning. There is also the potential 
for coastal drizzle, yet the probability is not great enough to 
include in the official forecast grids. 

For Saturday afternoon, we are expecting slightly cooler 
temperatures than today as stratus will be slower to clear. This is 
also in response to more zonal for developing over the region.

&&

.LONG TERM...
Issued at 1250 PM PDT Fri May 22 2026
(Saturday night through next Thursday)

Zonal flow will persist on Sunday, thus temperatures will be similar 
to those on Saturday as far as afternoon maximum temperatures go. 
During the late evening and overnight hours, cannot rule out coastal 
drizzle again Saturday night into Sunday morning. 

By late Monday and early Tuesday, a cold front associated with a 
deep upper level through is forecast to sweep across the region. 
This would result in drizzle and/or light rain as the front moves 
from north to south across the Bay Area and Central Coast. However, 
widespread rainfall is not expected and will be very light not 
amounting to much more than a few hundredths of an inch. In wake of 
the frontal passage, the marine layer may mix out and allow for 
coastal locations slightly warmer compared to this weekend. Winds 
are also forecast to strengthen over the coastal waters on Tuesday 
and Wednesday. 

From the previous forecaster: "Towards the later part of the week, 
the ensemble model runs begin to diverge as the evolution of the 
upper level low and incoming ridging becomes uncertain. Most runs 
lean towards a warming trend for that period, which is reflected in 
the current forecast, with a significant minority (around 30-40% of 
the runs) suggesting that some form of trough lingers through the 
period." 

&&

.AVIATION...
(06Z TAFS)
Issued at 901 PM PDT Fri May 22 2026

The stratus deck has begun its push onshore and is set to impact all 
terminals at some point (except for SJC and LVK) during the TAF 
period as the marine layer continues to deepen. Winds reduce through 
the night, thus allowing MVFR-IFR ceilings to develop. By Saturday 
late morning, winds will locally increase which will help to mix out 
the remaining low stratus in the area, confining the deck right off 
the coastline while still impacting HAF.

Vicinity of SFO...MVFR ceilings will develop around 09Z Saturday 
(though they may arrive a couple hours early) as the stratus 
intrusion continues onshore and marine layer deepens. The low 
ceilings begin to mix out late Saturday morning as moderate winds 
develop through the afternoon, shifting back to VFR through the TAF 
period with the potential for another round of MVFR ceilings 
Saturday night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...As winds diminish overnight, MVFR-IFR 
ceilings will prevail into late Saturday morning with slight impacts 
to visibility. Winds will increase Saturday morning which will mix 
out the stratus deck and push it offshore, shifting to VFR 
conditions for a short period. The marine layer is expected to push 
back onshore Saturday evening for another round of MVFR-IFR
ceilings.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 901 PM PDT Fri May 22 2026

Moderate to strong northerly breezes prevail in the northern outer
waters allowing rough seas to build in the surrounding area.
Conditions remain hazardous for small crafts in the aforementioned
area through Saturday morning. Elsewhere, west to southwesterly
winds will remain light to gentle with moderate wave heights. Seas
begin to gradually abate to moderate heights by midday Saturday
through early Tuesday morning. An incoming trough is set to
approach  our waters late Monday night, bringing strong
northwesterly winds  and building rough seas.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 AM PDT Saturday for Pt Arena to Pt 
     Reyes 10-60 NM.

&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Navarrete
MARINE...Navarrete

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Prepared by Boulder-Creek.com Weather at: Fri May 22 22:30:03 PDT 2026