247
FXUS66 KMTR 272155
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
255 PM PDT Fri Jun 27 2025

...New SYNOPSIS, SHORT TERM, LONG TERM, MARINE...

.SYNOPSIS...
Issued at 252 PM PDT Fri Jun 27 2025

June Gloom continues with cloudy coastal conditions, sunny
afternoons, and returning cloud cover each evening. Temperatures
peak across the interior today before a slight cool down this
weekend.

&&

.SHORT TERM...
(This evening through Saturday)
Issued at 252 PM PDT Fri Jun 27 2025

"June Gloom" remains the theme of the forecast with overcast
conditions during the night and early morning hours to continue for
much of this week. The marine layer is currently at a depth of about
1200-1500 ft on the Fort Ord Profiler with zonal upper level flow to
weak troughing maintaining the marine layer around its current depth
through the short term forecast. High temperatures on Saturday will
be in the 80s across the interior with temperatures across the
elevated terrain reaching into the low 90s. For coastal areas,
continued onshore flow and overcast conditions will keep
temperatures much cooler with highs in the 60s to low 70s.
Temperatures will generally be seasonal to slightly below normal
along the coastline and seasonal to slightly above normal across the
elevated terrain and interior valleys on Saturday.

For the month of June, temperatures have been seasonal to slightly
below normal at sites within and below the marine layer. For
example, the San Jose climate site has only reached 80+ degrees
twice so far this month with daily average temperatures running 2.6
degrees F below normal so far this month. This trend is seen at
other sites across the Bay Area and Central Coast but just how much
temperatures are running below normal ranges from site to site.
Other climate sites show average daily temperatures running below
normal at Oakland Museum (2.6 degrees F), Santa Rosa (0.4 degrees
F), San Francisco Downtown (2.3 degrees F), Napa State Hospital (3
degrees F), and Monterey (1.3 degrees F). This is in large part
thanks to continued onshore flow and persistent upper level
troughing over the Bay Area which allowed the marine layer to deepen
and brought cooler, moister air farther inland. As a refresher, the
marine layer is a surface based layer of cooler, moister air that
forms as a result of cold ocean water cooling the air directly above
it. When upper level troughing is observed, the marine layer is able
to deepen and spread farther inland, often resulting in cooler,
overcast conditions across the interior. Inversely, when upper level
ridging is observed, the marine layer compresses and stays confined
to the coastline. This typically results in clear skies and can
result in temperatures warming more significantly across the
interior. The classic monikers of "May Gray," "June Gloom," and
"Fogust" are often used to describe typical overcast summertime
conditions caused by the marine layer in coastal California. It is
important to note that all of the aforementioned sites are located
at elevations that fall within the marine layer. For sites across
the interior Central Coast and elevated terrain that are either
above or less impacted by the marine layer, temperatures are running
slightly warmer than normal. For example, daily average temperatures
at Pinnacles National Park are running 2.2 degrees F above normal
and 2.5 degrees F above normal at Mount Hamilton in Santa Clara
County. That is to say there is not a one size fits all answer as to
if temperatures have been cooler than normal this June as it really
depends on where you are and if you are within the marine layer or
not.

&&

.LONG TERM...
(Saturday night through next Thursday)
Issued at 252 PM PDT Fri Jun 27 2025

In the longer term forecast, not much changes as a weak upper level
trough arrives Sunday and continues our current pattern for much of
next week. Areas across the interior will largely be in the 80s
while areas within the elevated terrain (above the marine layer)
will be in the 90s. There is some potential for a weak shortwave
ridge to develop Wednesday to Thursday which will cause temperatures
to rise by 3-5 degrees. This is shortlived, however, with guidance
indicating a return to weak upper level troughing by Friday. Coastal
areas continue to benefit from the natural air conditioning that is
the marine layer with highs peaking in the upper 50s to 60s through
the rest of the week. What does this mean in terms of stratus
coverage? The daily pattern of stratus returning overnight and
clearing mid to late morning will continue for coastal regions and
portions of the Bay Area this week. If you`re looking for a pattern
change, it`s not likely until mid-July. Long range guidance shows
upper level troughing persisting through at least mid-July before
the pattern finally starts to shift to upper level ridging over the
Western US. The Climate Prediction Center continues near normal
temperatures across our CWA through July 10th before showing a
switch to above normal temperatures in the weeks 3-4 outlook (July
12th-25th). This is still a few weeks away so we`ll have to see how
the forecast changes as we approach mid-July.

&&

.AVIATION...
(18Z TAFS)
Issued at 1051 AM PDT Fri Jun 27 2025

Sky conditions have either scattered out or completely cleared as of
this writing. Onshore winds will increase this afternoon, yet are
forecast to be slightly weaker than previous days. Winds ease after
sunset and return to light/variable at most sites. Rather high
confidence for IFR/MVFR conditions to return to the Monterey Bay
terminals late evening or early Saturday morning with much lower
probabilities for the Bay Area terminals.

Vicinity of SFO...VFR conditions are expected to persist through the
forecast period. Onshore winds increase this afternoon with gusts up
to 20 kt. Low confidence for IFR/MVFR ceilings early Saturday
morning and have not included in the TAFs at this time. Any low
clouds that do develop will scatter out or clear by 16Z-18Z Saturday
with increasing onshore winds again by Saturday afternoon.

SFO Bridge Approach....Similar to SFO.

Monterey Bay Terminals...VFR conditions are expected to persist
through early this evening. Onshore winds increase this afternoon
before easing late this evening. High confidence for IFR/MVFR
ceilings to return late this evening and potentially lowering at
times to LIFR early Saturday morning.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 252 PM PDT Fri Jun 27 2025

Fresh to strong northwesterly breezes will continue over the
outer waters north of Point Reyes through Sunday. Moderate to
rough seas continue through Saturday morning, with significant
wave heights gradually subsiding into Sunday as winds ease. The
next round of elevated wave heights, strong northwesterly breezes,
and moderate to rough seas begins Tuesday and continues through
late next week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 AM PDT Saturday for Pt Arena to Pt
     Reyes 0-10 nm.

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

     Small Craft Advisory until 3 AM PDT Saturday for Pigeon Pt to Pt
     Pinos 10-60 NM.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...RGass
MARINE...RGass

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