Hercules, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

083
FXUS66 KMTR 271139
AFDMTR

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

...New AVIATION, MARINE...

.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...
(12Z TAFS)
Issued at 437 AM PDT Sun Jul 27 2025

Currently a mixed bag of LIFR-MVFR at the terminals. Interior
terminals will likely improve to VFR by this afternoon with stratus
sticking close to the coast - potentially impacting bayshore and
coastal terminals through the TAF period.

Vicinity of SFO...Currently IFR with westerly flow. If VFR is
achieved, it will likely be brief with high confidence in a return
of an IFR ceiling tonight. Westerly flow will prevail through the
TAF period.

SFO Bridge Approach...Low stratus clouds will likely linger between
OAK, SFO, and northward with a 20% chance that OAK and SFO will
not achieve VFR.

Monterey Bay Terminals...Currently IFR with southwesterly flow at
MRY and IFR with westerly flow at SNS. Brief VFR may be achieved
this afternoon, but low stratus will stick close to the coast with
high confidence in a return of IFR ceilings tonight. Westerly winds
will prevail through the TAF period.

&&

.MARINE...
(Today through Friday)
Issued at 437 AM PDT Sun Jul 27 2025

Moderate to fresh northwesterly breezes will prevail with
widespread strong gusts expected by tomorrow afternoon. Moderate
to rough seas and low clouds with drizzle will prevail through
Thursday.

&&

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

     Small Craft Advisory from 3 AM to 9 AM PDT Monday for Pt Arena
     to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Sarment
MARINE...Sarment

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