Altadena, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

188
FXUS66 KMTR 070138
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
638 PM PDT Fri Jun 6 2025

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 103 PM PDT Fri Jun 6 2025

Mostly quiet conditions prevail through the forecast period with
warm temperatures inland and cool, seasonable temps along the
coast. Slight cooling trend by the middle of next week as a deeper
trough pattern develops off the West Coast.

&&

.SHORT TERM...
(This evening through Saturday)
Issued at 103 PM PDT Fri Jun 6 2025

Stratus quo, deja vu, groundhog day, whatever you want to call
it. Inland areas heating up to comfortable and seasonable
temperatures today while the coastline is once again leaving folks
in a paralyzing state of "should I bring a jacket". Then they
don`t because it feels nice at first and end up regretting it 30
minutes later. This trend generally continues into the weekend
with inland locations heating up by a few more degrees while
coastal locations remain in this cool but nice state with near
normal temperatures. A few coastal locations will see temps a bit
more tolerable for short sleeves and shorts such as Santa Cruz,
Big Sur, and Monterey (for like a couple of hours). Are
convertible pants still a thing? I digress.

&&

.LONG TERM...
(Saturday night through next Thursday)
Issued at 103 PM PDT Fri Jun 6 2025

Really not much change into the end of the weekend with the upper
level ridge mostly staying put, and nothing to drive the weak
closed low away. Therefore, the pattern is slow to revert. By the
middle of the week, guidance depicts a deeper open wave trough
that would kick off a cooling trend into late next week. Ensemble
guidance has been greatly confident in advertising this whole
pattern evolution over the next several days. All-in-all, most
people aren`t going to notice much day-to-day difference before
the middle of next week with the exception of the inland areas
recognizing that their car thermometer says 82 instead of 80.

&&

.AVIATION...
(00Z TAFS)
Issued at 638 PM PDT Fri Jun 6 2025

It`s VFR except for stratus /MVFR possibly IFR/ along the immediate
coastline per surface observations and satellite imagery. A weak
low pressure area straddles the CA coastal waters and offshore waters.
The latest NAM and HRRR output are having trouble resolving the
strength of the southerly SMX-SFO, SNS-SJC and STS-UKI pressure
gradients and winds associated with the somewhat distant low.
Southerly winds are resulting in a combination of the usual
southerly downsloping and drying influences into the marine layer
while also drawing in late afternoon drier air continental
influence in return flow typical of afternoon thermally direct
seabreeze circulations.

In this current pattern KHAF stands with a high probability of
ongoing MVFR which may become IFR later this evening to early
Saturday since the late afternoon Oakland upper air sounding
showed a lowered temperature inversion based at 1100 feet (vs 2000
feet base early this morning on the 12z sounding). KSTS and KOAK
with southerly wind and northwesterly wind respectively will
likely see a stratus intrusion during the mid evening. KSNS will
likely see stratus before KMRY due to wind flow across the
Monterey Peninsula and the Monterey Bay that resembles a southerly
wind reversal. Post sunset pressure gradients will ease in
response to nocturnal cooling and subsequently a decrease in land
vs sea surface temps, leaving the onshore SFO-SAC pressure
gradient/wind to usher in stratus and/or fog tonight and Saturday
morning. The marine layer depth varies from several hundred feet
to 1700 feet.

The aforementioned low pressure area will slowly drift southwest
tonight and Saturday, which should allow a surface ridge of high
pressure to build in over the coastal waters mainly resulting in
strengthening SFO-SAC pressure gradient/wind this time tomorrow;
just don`t know with certainty, will have to closely monitor.

Vicinity of SFO...Currently 300-310 wind direction, marine layer
depth approx 1100 feet vicinity KSFO and momentum of southerly
winds along the ocean side of the SF Peninsula will help keep VFR
going through early evening. Uncertain on timing of stratus
intrusion, for now tempo group is 04z-08z this evening for MVFR
then transitioning to IFR based on RAP/HREF output. RAP model is
pessimistic with low ceiling tonight and Saturday morning at
KSFO. Current forecast indicates VFR returning by late morning
Saturday (RAP model is near 100% humidity near surface thru 17z
Saturday). West to northwest wind gusting to 25 knots through 04z
this evening, near 10 knots overnight and Saturday morning, west
to northwest wind increasing to 25 knots Saturday afternoon and
early evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently the surface pressure gradient,
wind and visible satellite pattern resembles a southerly wind
reversal from the Monterey Bay area to the northern Salinas
Valley. It`s a challenging coastal stratus/fog pattern for
aviation from the Bay Area to the north Central Coast since the
model forecasts are not really seeing the pattern. With onset of
nocturnal cooling the gradient field will ease with the onshore
winds likely predominating later in the evening. In the meantime,
the area terminals will have ongoing VFR until later in the
evening, then increasing probability of IFR developing, with IFR
prevailing tonight and Saturday morning. Stratus and any lingering
patchy fog will mix out late Saturday morning. Winds becoming
mainly onshore during the evening and overnight 5 to 10 knots.
Onshore winds Saturday afternoon and early evening 10 to 15 knots.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 544 PM PDT Fri Jun 6 2025

A gentle to moderate southerly breeze continues across the
coastal waters before becoming more westerly on Saturday. Diurnal
effects will bring a fresh to strong SW breeze to the San
Francisco Bay over the next couple afternoons. Otherwise
conditions will be favorable through early next week when winds
start to build and a long period southwesterly swell arrives.
Winds and seas will rebuild more substantially mid to late next
week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT this evening for SF Bay N of
     Bay Bridge.

     Small Craft Advisory from 3 PM to 9 PM PDT Saturday for SF Bay N
     of Bay Bridge.

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Canepa
MARINE...RGass

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