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
From the National Weather Service
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