Portola Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

579
FXUS66 KMTR 050528
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1028 PM PDT Wed Jun 4 2025

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 1231 PM PDT Wed Jun 4 2025

Fair weather continues over the next several days with cloudy
mornings and clear afternoons. Temperatures around seasonal
normals with a slight warming trend into next work week.

&&

.UPDATE...
Issued at 820 PM PDT Wed Jun 4 2025

Forecast remains on track tonight with satellite showing our
coastal areas beginning to fill in with low marine stratus,
similar to what we saw at this time last night. The marine layer
will be slightly more compressed tonight which may lead to more
coverage in light drizzle and patchy fog by early Thursday
morning.

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 1231 PM PDT Wed Jun 4 2025

Very typical seasonable set up going on right now across the
region. One notable aspect going on today is a weak surface low
in response to a subtle upper-level shortwave trough. That has
resulted in temps a few degrees cooler than yesterday, and will
likely reinforce some marine stratus and onshore flow for areas
south of the SF Bay Thursday morning. Otherwise, Thursday looks
like another beautiful day to get outside. Temps closely mirroring
that of today with the marine layer deepening slightly, cooling
off the coast by a couple of degrees.

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 1231 PM PDT Wed Jun 4 2025

Subtle warming trend on tap into the weekend with an interesting
twist. Guidance depicts a subtle cutoff low that meanders off the
CA coast into the weekend. Amid a strong ridge that will heat up
most of the west, this cutoff low will likely again reinforce
onshore flow and keep the marine layer intact. Thus, our temps
appear to be moderated by this feature and may actually result in
very little noticeable change in the weather through the weekend
for most folks. Some hints at larger scale troughing after the end
of the extended period, which would result in a more noticeable
pattern change. Details on that will be more clear in the coming
days.

&&

.AVIATION...
(06Z TAFS)
Issued at 1027 PM PDT Wed Jun 4 2025

Currently VFR with breezy northwest winds observed at most sites. A
fairly substantial stratus bank is just offshore with CIGs expected
to build in overnight. The marine layer looks to compress to between
500 to 1000 ft overnight which will result in IFR to MVFR CIGs
across portions of the Bay Area. Moderate confidence that LIFR-IFR
CIGs will develop along the coastline impacting HAF, MRY, and SNS.
Fog becomes more likely after 12Z across the North Bay Valleys
tomorrow morning which could result in LIFR conditions at least
temporarily developing there. Winds ease overnight, shifting
southerly to becoming variable at times, before moderate southwest
to northwest winds redevelop during the day.

Vicinity of SFO...Gusty northwest winds will ease overnight before
gradually shifting southerly early Friday morning. Patchy MVFR CIGs
are expected to fill into the SF Bay overnight but this is expected
to be temporary. This is a slightly more optimistic TAF with the NBM
and LAMP guidance indicating that stratus may persist through mid to
late tomorrow morning. VFR conditions return by mid to late morning
with winds shifting more southwest to westerly and strengthening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...CIGs are expected to build back in early
this evening with highest confidence in CIGs arriving between 02-03Z
with some guidance indicating an earlier arrival closer to 01Z is
possible at MRY. Moderate confidence that LIFR CIGs will effect MRY
overnight with low to moderate confidence that LIFR CIGs will impact
SNS. CIGs look to rise between 15-18Z with full clearing expected
after 18Z. Clearing will be short lived with stratus looking to
return just after the end of this TAF period. Moderate onshore winds
continue this evening before weakening overnight, becoming southerly
to variable at times.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 1027 PM PDT Wed Jun 4 2025

Gale conditions continue over the northern outer waters before
winds  ease early Thursday morning. Breezy to gusty winds and
hazardous  conditions for small crafts will then continue over the
northern  outer waters through late Thursday morning. Breezy fresh
to strong  winds continue within the San Pablo Bay and the inner
coastal waters  from Point Reyes to Pigeon Point as a southerly
coastal jet  develops. Wave heights over the outer coastal waters
will continue  to abate through the end of the week with
significant wave heights  to drop below Small Craft Advisory
levels by Friday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Friday for SF Bay N of Bay
     Bridge.

     Small Craft Advisory until 9 PM PDT Thursday for Pt Reyes to
     Pigeon Pt 0-10 nm.

     Gale Warning until 3 AM PDT Thursday for Pt Arena to Pt Reyes 10-
     60 NM.

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Kennedy
MARINE...Kennedy

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