FXUS66 KMTR 201204
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
504 AM PDT Wed May 20 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1036 PM PDT Tue May 19 2026
- Diurnally driven winds, with onshore winds during the afternoon
and early evening.
- Above normal temperatures continue through midweek with seasonal
temperatures returning late week.
- Warm and dry weather through Thursday leads to elevated fire
weather concerns for the interior Bay Area and Central Coast.
&&
.SHORT TERM...
Issued at 1036 PM PDT Tue May 19 2026
(Tonight through Thursday)
Little change in the forecast as high pressure slowly creeps into
Northern California today. Satellite imagery this evening shows
high clouds sliding down the West Coast, with much of the Bay Area
likely seeing some cirrus. With the current data, temperatures
look to be on track; however, if we're not able to get radiational
cooling, our temperatures for tonight might be low/cool. This
would be because the clouds act as blanket, allowing less heat to
escape at night. It'll be something to keep an eye on over the
next few hours.
In terms of Wednesday, if you guessed, "No pattern change. Ha, this
means another day of warmer weather", you'd be correct! A potential
fly in the ointment is if the marine layer attempts to manifest
around 500 feet. This might keep temperatures a few degrees cooler
along the immediate coast, but elsewhere temperatures should be
similar to Tuesday, perhaps a few degrees higher.
&&
.LONG TERM...
Issued at 1036 PM PDT Tue May 19 2026
(Thursday night through next Tuesday)
No major changes to the extended forecast. Upper level troughing
looks to keep hold over the western US, while the Pacific high
pushes even more into northern California on Thursday. With the high
being a bit more pronounced, another warm day will be on tap.
After that, guidance has flow becoming quasi-zonal for a brief
period before troughing returns on Friday. The marine layer looks
to be around 500ft on Thursday, deepening to around 1000ft by
Friday and then lasting through the weekend. With onshore flow, a
deeper marine layer, and troughing through the weekend the NBM's
temperatures are bit too warm. Opted to start trending towards
slightly cooler temperatures given the ensembles and cluster
analysis. But there is a chance ridging wins out and temperatures
might warmer. Definitely something to keep an eye on over the next
few days.
&&
.AVIATION...
(12Z TAFS)
Issued at 503 AM PDT Wed May 20 2026
VFR at the big three this morning and expect that to continue
despite some stratus forming offshore. Guidance was a little too
aggressive in bringing in stratus elsewhere and thus have cut
back on stratus this morning. HAF and SNS are experiencing some
hz/br drop the flight CAT. VFR this afternoon gusty onshore flow.
Gusts 15-20kt seems reasonable. For tonight, marine layer
currently off the coast will move locally inland with highest
conf for HAF and MRY/SNS.
Vicinity of SFO...VFR. NW winds ramp up this afternoon with gusts
to 20kt.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...MRY is VFR, but enough low level moisture
is at SNS to have occasional br/hz. Much higher conf for stratus
intrusion tonight into Wednesday.
&&
.MARINE...
(Today through Monday)
Issued at 432 AM PDT Wed May 20 2026
A weak frontal boundary to the north will maintain fresh to strong
northerly breezes and rough seas over the outer waters north of
Pigeon Point through early Thursday. Elsewhere, moderate to fresh
northerly breezes and moderate seas will prevail. Conditions
improve into the weekend as seas and northwesterly breezes become
moderate.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 PM PDT Thursday for Pt Arena to Pt
Reyes 10-60 NM.
&&
$$
SHORT TERM...KR
LONG TERM....KR
AVIATION...MM
MARINE...MM
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Prepared by Boulder-Creek.com Weather at: Wed May 20 06:30:02 PDT 2026
From the National Weather Service
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