FXUS66 KMTR 020005
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
505 PM PDT Fri May 1 2026
...New UPDATE, AVIATION, MARINE...
.KEY MESSAGES...
Updated at 125 PM PDT Fri May 1 2026
- Overnight and morning stratus will persist as the marine layer
deepens through the weekend
- Cooler temperatures this weekend with a chance of drizzle
and/or light rain, mainly along the coast, into early next
week
- Warm and dry condition's return the middle of next week
&&
.UPDATE...
Issued at 502 PM PDT Fri May 1 2026
The forecast appears to be on track. High clouds are passing
overhead, with stratus seeping into the coast due to the deepening
marine layer. This looks to deepen this evening and overnight,
perhaps to 1500 to 2000ft.
&&
.SHORT TERM...
Issued at 125 PM PDT Fri May 1 2026
(This evening through Saturday)
We'll lose the influence of the upper ridging moving across our area
this afternoon by sunset, with a pattern shift to persistent
troughing through the weekend into the beginning of next week.
Stratus has mostly retreated back to the coastline with San
Francisco and SF Peninsula lagging a little behind early this
afternoon. Otherwise expect mostly sunny skies with a layer of thin
cirrus for the remainder of the day. As an upper low continues
tracking south offshore toward our latitude, we'll see the marine
layer continue to gradually increase through the weekend. Stratus
development tonight and its intrusion inland will be similar as what
we saw last night into this morning. With the slight increase in the
depth of the marine layer as well tonight, it should take a little
longer to mix out Saturday, into the early afternoon for adjacent
inland spots, and potentially linger most if not all day for
immediate coastal areas. There is a chance of drizzle along the
coast late tonight into Saturday morning with the best chances in
higher elevated coastal ranges.
&&
.LONG TERM...
Issued at 125 PM PDT Fri May 1 2026
(Saturday night through next Thursday)
The increased cloud clover inland and cooler temperatures will lead
to a more notable drop in inland high temperatures this weekend,
around 5 degrees from todays values on Saturday and another 5 on
Sunday, with little change for coastal areas under the continuous
influence of the marine layer. As the Rex Block begins to pivot
inland, so too will the offshore upper low, beginning to take a more
direct path inland on Sunday. The cooling trend will continue into
the beginning of next week. By Monday and Tuesday, high temperatures
will bottom out to between 5-10 degrees below normal as the system
tracks inland into the desert southwest. Unfortunately, this system
has continued to trend drier from already anemic moisture offered in
guidance earlier this week. As mentioned above, there will be
patches of drizzle at times mostly confined to the coast but with
no impacts. Wednesday appears to be the beginning of an extended
period of warm and dry weather under persistent ridging well
beyond the current forecast period.
&&
.AVIATION...
(00Z TAFS)
Issued at 502 PM PDT Fri May 1 2026
High clouds stream over the region this afternoon, with stratus
deepening along portions of the coast. Expect another night of MVFR
cigs at most terminals, with the possibility for IFR in the North
Bay Valley terminals, KHAF, and around the Monterey Bay. Stratus
should have a similar onset to last night, if not a few hours
earlier. The marine layer is expected to deepen to about 1500-
2000ft, which means it may take a little longer to erode tomorrow.
Most sites should start seeing cigs lift by mid morning and mix out
by the late morning or early afternoon hours. This will likely be
short lived as stratus looks to make another surge Saturday night
into Sunday morning. Medium to high confidence in the forecast.
Vicinity of SFO...Stratus is slowly filtering in from the west and
gradually filling through the San Bruno Gap. Expect stratus to
arrive at the terminal within the next couple of hours, with a nigh
of MVFR cigs. Model guidance suggests the stratus holds on a little
bit longer tomorrow morning perhaps lifting above MVFR around 20Z.
We should get a brief period of VFR cigs from 20-23Z, with stratus
returning for tomorrow evening. Medium to high confidence in the
forecast.
SFO Bridge Approach...Similar to SFO. MVFR cigs should cover the
northern portion of the bay this evening and cover the southern half
of the San Francisco Bay after midnight. Clouds tomorrow should lift
or mix out over the southern half of the bay, while the northern
side takes a bit longer to clear. Low to medium confidence.
Monterey Bay Terminals...Satellite this afternoon looks very
familiar, with a tendril of stratus covering KMRY and entering into
KSNS's air space. The question is, will it behave similarly?
Meaning, KMRY remained socked in but KSNS had a brief stint of VFR
cigs yesterday evening. Opted to go with the more pessimistic
forecast but will need to keep an eye on KSNS in case the stratus
does decide to meander a bit. Once it returns, MVFR to IFR cigs are
expected overnight and into Saturday morning. Cigs begin to lift
late morning and into the early afternoon, though stratus returns
tomorrow evening. Medium to high confidence in the forecast.
&&
.MARINE...
(Tonight through next Thursday)
Issued at 502 PM PDT Fri May 1 2026
A fresh to strong northwesterly breeze continues into Saturday
before winds diminish. Winds will become moderate to fresh late
Saturday into Sunday. Moderate, wind driven, seas will build to 8
to 10 feet across the northern outer through Saturday afternoon.
Seas subside late Saturday into Sunday as winds continue to
diminish next week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from Saturday morning through Sunday
evening for CAZ006-505-509-529-530.
PZ...Small Craft Advisory until 9 AM PDT Saturday for Pt Arena to Pt
Reyes 0-10 nm.
Small Craft Advisory until 3 PM PDT Saturday for Pt Arena to Pt
Reyes 10-60 NM.
&&
$$
SHORT TERM...JM
LONG TERM....JM
AVIATION...KR
MARINE...RGass
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Prepared by Boulder-Creek.com Weather at: Fri May 1 22:30:02 PDT 2026
From the National Weather Service
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