Portola Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

475
FXUS66 KMTR 060431
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
931 PM PDT Sat Jul 5 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 131 PM PDT Sat Jul 5 2025

 - Temperatures remain below seasonal averages into early next week.

 - Marine layer increases and expands farther inland for end of the
   weekend and continues into early next week.

 - Gradual pattern change which will bring a warming trend
   starting Wednesday.

&&

.SHORT TERM...
Issued at 131 PM PDT Sat Jul 5 2025
(This evening through Sunday)

Near zonal flow will give way to an upper level low that has formed
off the Northwest Coast of CA this afternoon. This will slowly slink
meander to the south and then look to hold off our coast through
Sunday. This will lead to seasonably cool temperatures continuing
and lead to a deepening marine layer. For now, mostly clear skies
are observed across much of the Bay Area and Central Coast with
stratus clinging to the San Francisco/San Mateo coasts. Stratus is
expected to fill back in later this evening and into tonight, and
should seep into coastal valleys by Sunday morning. The clouds
should retreat to the coast by late Sunday morning or early Sunday
afternoon.

&&

.LONG TERM...
Issued at 131 PM PDT Sat Jul 5 2025
(Sunday night through next Friday)

A closed low should sit off just to our west through the early
portion of the work week, which will allow the marine layer to
deepen. Look for nighttime and morning clouds through midweek, with
perhaps some coastal drizzle Monday night and again Tuesday night. A
pattern change will start around Wednesday which is when ensemble
and cluster analysis show the ridge over the Desert Southwest
strengthening. Temperatures should increase for the later portion of
the week, with Thursday and Friday looking to be the warmest at this
time. It`s still too early to say how warm we`ll get as this time,
especially since models struggle with how strong the ridge will get.

&&

.AVIATION...
(06Z TAFS)
Issued at 930 PM PDT Sat Jul 5 2025

Currently a mixed bag of IFR-VFR at the terminals with stratus along
the coast and beginning to intrude inland. The marine layer is
currently being observed at 1,400 feet on the Fort Ord profiler. A
cutoff low off the coast will promote onshore winds, the deepening
of the marine layer, and coastal drizzle. Moderate to high
confidence on all terminals deteriorating below VFR tonight - likely
low-end MVFR to IFR ceilings for all but the coastal terminals of
HAF, MRY, and SNS which are expected to have LIFR ceilings - with
confidence lowering the farther inland the terminal is. Widespread,
albeit brief for some, VFR is likely by tomorrow afternoon (with the
exception of HAF which will likely remain MVFR) with stratus
sticking close to the coast during the afternoon.

Vicinity of SFO...Currently MVFR with westerly flow. High confidence
in VFR prevailing by tomorrow afternoon. Westerly winds will prevail
through the TAF period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently IFR with southwesterly flow at
MRY and MVFR with northwesterly flow at SNS. Moderate to high
confidence in MRY and SNS further deteriorating to LIFR with the
HREF giving 80% and 60% probabilities respectively. Brief VFR is
expected by tomorrow afternoon with stratus sticking close to the
coast in the afternoon. Westerly winds will prevail through the TAF
period.

&&

.MARINE...
(Tonight through next Friday)
Issued at 930 PM PDT Sat Jul 5 2025

Strong northwesterly breezes will continue through Sunday for the
outer waters and coastal jet regions of Point Reyes and Point Sur.
Winds diminish Monday with moderate to fresh breezes forecast
through Wednesday along with wind shifts from a surface low.
Moderate to rough seas will prevail through Wednesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 AM PDT Sunday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt
     Piedras Blancas 0-10 nm.

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

&&

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...Sarment
MARINE...Sarment

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