FXUS66 KMTR 230943
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
243 AM PDT Sat May 23 2026

...New MARINE...

.KEY MESSAGES...
Updated at 1200 AM PDT Sat May 23 2026

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

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

&&

.SHORT TERM...
Issued at 1200 AM PDT Sat May 23 2026
(Today and tonight)

Extensive stratus has developed along the coast and has flowed into 
the North Bay valleys, the northern part of the East Bay, the 
Monterey Bay region, and the Salinas Valley. Readings from the 
Bodega Bay profiler reveal a marine layer depth of around 2000 feet, 
which would allow for extensive inland coverage of marine layer 
stratus this morning and would limit the clearing of stratus through 
the afternoon hours. The upper level pattern is also promoting zonal 
flow across the state, reinforcing the cooler and milder conditions. 
Thus, today's highs are a little cooler than yesterday's as the 
inland valleys reach the 70s and the lower 80s, while areas near the 
bays see highs in the middle 60s to lower 70s and the Pacific coast 
hovers in the upper 50s. Breezy onshore winds will develop during 
the afternoon and evening hours with gusts up to 20 mph through 
favored gaps and passes.

&&

.LONG TERM...
Issued at 1200 AM PDT Sat May 23 2026
(Sunday through Friday)

A slight cooling may be noticeable in the inland valleys on Sunday 
with high temperatures up to 5 degrees cooler, but otherwise 
conditions will be similar to today with extensive morning stratus 
and breezy onshore winds in the afternoon and evening hours. The 
cooling trend continues through the early part of next week with a 
cold front associated with a deep upper level low expected to sweep 
through the region sometime on Tuesday, with temperatures in the 70s 
across the interior valleys, the middle to upper 60s near San 
Francisco bay and Santa Cruz, and the upper 50s to lower 60s near 
the Pacific coast and the southern Monterey Bay region. Breezy winds 
will develop across the region with strong gusts through the favored 
gaps and passes. Although there is a very slight chance (around 10% 
probability) of light showers or drizzle popping up in the coastal 
regions, widespread wetting rains (rain totals at least a tenth of 
an inch) are not expected. 

Gradual warming is expected once the cold front passes on Wednesday, 
with lingering northerly winds sparking some early concern for 
elevated fire weather risks in the interior, although it's a little 
too early to pin down exact details at this point. I'm not one 
hundred percent sold on warming on the scale that the NBM model 
output depicts, but it does appear that temperatures in the 80s are 
at least possible for the inland valleys. Beyond the 7-day outlook, 
the forecast becomes more uncertain as ensemble members differ on 
how quickly that upper level low fills in and how the pattern 
evolves when it does. The CPC outlook leans towards temperatures 
warmer than the seasonal average (highs around 65 degrees for 
downtown San Francisco) and precipitations totals near the seasonal 
average (rain totals around one or two hundredths of an inch of rain 
per day for downtown San Francisco) for the last couple days of May 
into the first week of June. 

&&

.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...
(Today through Thursday)
Issued at 242 AM PDT Sat May 23 2026

Moderate to strong northerly breezes will gradually decrease this
morning over the northern outer waters allowing rough seas to
gradually subside as well. Conditions remain hazardous for small
crafts in the aforementioned area through 9AM Saturday morning.
Elsewhere, west to southwesterly winds will remain light to gentle
with moderate wave heights. Seas abate to moderate heights by
midday Saturday and then hold 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 this morning for Pt Arena to 
     Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Navarrete
MARINE...KR

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Prepared by Boulder-Creek.com Weather at: Sat May 23 04:30:03 PDT 2026