374
FXUS66 KMTR 270855
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
155 AM PDT Sun Jul 27 2025

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 1209 AM PDT Sun Jul 27 2025

 - Temperatures warm slightly while remaining below seasonal
   normal through the week.

 - Strong onshore afternoon winds will gradually increase through
   mid-week.

&&

.SHORT TERM...
Issued at 1209 AM PDT Sun Jul 27 2025
(Today and tonight)

The marine layer has compressed to around 1,600 feet according to
the 00Z sounding, although the Ft. Ord profiler has indicated some
expansion since then. The current stratus deck is fairly similar
to 24 hours ago, with slightly less inland extent. The cloud
ceilings are generally below 1,000 feet and falling, which could
help bring another round of early morning drizzle to the typical
locations. The basic 500 mb pattern is troughing offshore,
extending from low pressure in the Gulf of Alaska, and high
pressure over the Gulf States. California is centered between
these two synoptic features. The high pressure will nudge the
trough a little today. This will cause the 850 mb temperature to
rise and max temperatures are expected to climb anywhere from 2-5
degrees compared to yesterday. Otherwise it will be pretty
similar with morning clouds, a clear breezy afternoon, and clouds
returning in the evening. Despite the modest warming, we are still
expected to stay below the seasonal normal.

&&

.LONG TERM...
Issued at 1209 AM PDT Sun Jul 27 2025
(Monday through Saturday)

The pattern described above is pretty stable, though there is a
gradual long term trend. The Gulf of Alaska is a well known storm
graveyard, and the 500 mb low there will gradually fill over the
next several days. Meanwhile the subtropical high over the Gulf
States will gain strength and push west. This feature will
eventually extend a ridge from Texas to eastern Washington. At
the surface this evolution will lead to a gradual increase in the
N-S pressure gradient between subtropical high pressure offshore
and a thermal low over Arizona. The Eureka to Santa Barbra
gradient is currently around 1 mb and will reach 6 or 7 mb by mid
week. Meanwhile the E-W gradient will remain fairly steady. The
SFO-SAC and SFO-WMC gradients remain positive and diurnally
driven according to a confident 2 km WRF ensemble. All these
means that winds will remain onshore (good for fire weather) while
the strength increases through the next several days. The 850 mb
temperature will also gradually increase from around the 25th
percentile today to around 75th percentile by Wednesday. This will
translate to a very slight warming trend, however the onshore
wind will be the primary driver, and keep most areas slightly
cooler than normal. Higher elevations will feel the warmer and
drier air mass, however. Regarding fire weather, all regions are
enjoying fuel moisture well above normal, but the forecast is for
the trend to reverse starting Monday, especially above the marine
layer.

&&

.AVIATION...
(06Z TAFS)
Issued at 958 PM PDT Sat Jul 26 2025

MVFR-IFR stratus expands from the coast into the Bay Area valleys
and the Monterey Bay region. Stratus will mix out across the inland
regions through Sunday morning and early afternoon while the coastal
areas remain socked in. Breezy onshore winds continue to diminish
over the next few hours, becoming light through Sunday morning
before resuming in the afternoon. Sunday evening, expect some inland
stratus to return although gradual compression of the marine layer
might limit the inland extent of the ceilings.

Vicinity of SFO... MVFR-IFR stratus through Sunday morning. Stratus
dissipates early Sunday afternoon, with the terminal remaining VFR
for a brief period before getting socked in again during the late
afternoon and early evening hours. Even then, expect the stratus
deck to lurk just to the north of the terminal. Breezy and gusty
west winds continue to diminish through the next few hours, becoming
light through Sunday morning before resuming in the afternoon.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... MVFR-IFR through Sunday morning, with the
inland regions clearing out by the early afternoon. Low probability
(20-30%) that MRY remains socked in through the day, but model
output currently shows a brief period of clear skies in the
afternoon hours. Stratus returns in the early evening. Light winds
continue overnight before breezy onshore flow returns Sunday
afternoon.

&&

.MARINE...
(Tonight through next Friday)
Issued at 807 PM PDT Sat Jul 26 2025

High pressure maintains northerly flow over the coastal waters
through the next week. Winds will increase locally on Sunday
afternoon north of Point Reyes and south of Point Sur. Moderate
seas prevail through the weekend then gradually increase beginning
Monday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this
     evening for Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Monday
     for Pt Pinos to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...DialH
MARINE...DialH

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