Tiburon, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

316
FXUS66 KMTR 100444
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
943 PM PDT Fri May 9 2025

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 1207 PM PDT Fri May 9 2025

Clear skies and warm temperatures will continue through Saturday
before a cold front brings much cooler temperatures, strong winds
and a chance for rain starting Sunday.

&&

.UPDATE...
Issued at 854 PM PDT Fri May 9 2025

As noted below temperatures were the bigger weather impact focus
for today. It was a warm one with many locations well above normal
for this time of year. Why so warm? Ridge of high pressure and
warm airmass aloft. KOAK sounding from 00Z showed 500mb heights
near 5800m and 850mb temps around 17C, both of which are near the
90th percentile for KOAK sounding records. That being said, it
wasn`t warm everywhere. Areas along the immediate coast were still
pretty chilly with highs stuck in the upper 50s to lower 60s. Sea
surface temps are similar and in the mid 50s to lower 60s. Once
you get away from the marine influence areas were able to tap into
the warmer airmass as temps soared into the 80s, 90s, and even
over 100 degrees. Hottest reliable station is the Bradley RAWS in
southern Monterey, which hit 101 degrees. Side note, that`s where
the ongoing Heat Advisory is in effect. Under these weather
regimes it`s also impressive to see the drastic spread of
temperatures across a short distance. The city of San Francisco
for instance saw temperatures of 58-59(Ocean Beach/Golden Gate)
today, but east side near Fisherman`s Wharf hit 75-78 degrees.

So for tonight, almost a repeat of last night. A shallow marine
layer will once again hug the immediate coast and locally nudge
inland around Monterey Bay. Relief will be felt in these
locations, but outside of the marine layer influence temperatures
will be milder and drier, most notably over the highest terrain.

No update needed this evening...will just be watching how much
stratus actually develops along the coast.

&&

.SHORT TERM...
(This evening through Saturday)
Issued at 1207 PM PDT Fri May 9 2025

Temperatures are running about 10 degrees warmer than this time
yesterday as a substantial 500 mb ridge of high pressure builds
over southern California. This ridge is compressing the marine
layer to about 500 feet, which is keeping the skies clear for most
of the region, though some on the immediate coast could see the
marine layer fog monster ruin their picnic in the early afternoon.
Otherwise temperatures are on track to reach the forecasted highs
(generally upper 80s for the inland valleys and upper 60s to low
70s along the coast). Winds are generally light to moderate and
onshore. Saturday will essentially be a repeat of Friday with
temperatures remaining well above normal, although there will
likely be some high clouds and increasing winds in the evening.
These changes are signaling a major shift in the weather pattern
going into Sunday.

&&

.LONG TERM...
(Saturday night through next Thursday)
Issued at 1207 PM PDT Fri May 9 2025

A deep trough will approach the west coast by Sunday. This system
will bring several days of disturbed weather, highlighted by much
cooler temperatures and strong onshore winds. The temperature
swing from Saturday to Sunday is notable for the Bay Area. For
example, the high forecast for Santa Rosa drops from 85 to 68
across the 2 weekend days. I checked to see when the last time
we`ve had a big drop like that, and it turns out it wasn`t that
long ago. From March 25-26 the high actually dropped further from
85 to 57. The trough will continue to dig south through Tuesday
morning, further decreasing temperatures. This system will also
bring strong onshore wind. The 500 mb winds should peak around 90
kts Monday afternoon, and will spend most of the day above 50 kts.
With cold air aloft decreasing the vertical stability, 40-50% of
this wind speed can mix down to the surface, equating to
occasional wind gusts reaching as high as 50 mph. Our official
forecast is more conservative with gusts in the 20-30 mph range.
The windiest times will be when the atmosphere is well mixed
Sunday and Monday afternoon/evening, especially in higher
elevations. We are also expecting some rain from this system,
mainly confined to Monday as the front moves through. Most of the
cwa has a chance of some rain, with up to 1/4" expected in the
North Bay. The NBM continues to lag behind other guidance in both
POP and QPF, and I`ve adjusted the forecast to find a good middle
ground in these variables. Finally, the cold air mass aloft and
lingering low-level moisture will create some instability late
Monday-Tuesday in the post frontal environment. The upper level
trough will still be over the west coast and could easily spin off
short wave triggers for strong convection. There is a slight
chance for thunderstorms both Monday and Tuesday, but all we can
say for now is that the ingredients are there. We don`t know if
they will all line up at the right time yet. Otherwise the weather
will begin to stabilize mid week as a ridge starts to rebuild,
inland temperatures recover back to seasonal norms, and the
typical marine layer pattern returns.

&&

.AVIATION...
(06Z TAFS)
Issued at 943 PM PDT Fri May 9 2025

A surface high pressure ridge remains approx 400 miles west and
northwest of the Bay Area with clockwise winds around the high
resulting in northwest winds across the coastal waters. Satellite
imagery shows patchy coastal stratus and fog, elsewhere over the
coastal waters it`s dry enough to support clear /VFR/. The surface
pattern is situated underneath a strong (90th percentile) 500 mb
high pressure system extending northward from SoCal, subsidence
continues to compress the marine layer to near sea level.

It`s a high confidence VFR forecast for the Bay Area airports
through the evening except for coastal stratus developing at KHAF
by mid to late evening. Sufficient late day mixing with drier air
helped extend KMRY and KSNS VFR conditions so far this evening.
However, not fully discounting the 18z/00z NAM 1000 mb humidity
forecasts which lean heavily toward stratus and fog /IFR-LIFR/
redevelopment along the coastline tonight and Saturday morning,
decided to lower visibilities and ceilings early Saturday morning
for the KMRY and KSNS TAFs. Recent NAM output has sped up a few
spot specific 925 mb cooling for Saturday compared to yesterday`s
output. Forecast confidence lowers somewhat with respect to
potential areal stratus/fog coverage late tonight to Saturday
since we`re on the western side of a soon eastward departing 500
mb high pressure system (strongest compression moving with it) and
some disagreement between the HRRR and NAM humidity forecasts for
tonight and Saturday. Fairly thorough cooling is forecast to take
place Saturday and Saturday night throughout the troposphere which
will favor increasing stratus and fog, onshore winds supporting an
inland intrusion later Saturday and Saturday night.

Vicinity of SFO...High confidence VFR forecast for the evening
since the marine layer is compressed to near sea level. Low to
moderate confidence VFR continues late tonight and Saturday
morning. West wind through the 06z TAF, increasingly gusty
Saturday afternoon and evening with IFR-MVFR on the ocean side of
the peninsula and increasing probability of MVFR reaching KSFO
Saturday evening and night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Moderate to high confidence VFR continues
through mid evening, thereafter there`s an increasing probability
of stratus and fog /IFR/ developing for tonight and Saturday morning.
Steady cooling Saturday should increase the marine layer depth
during the day, best chance of VFR will be from late morning to
the afternoon though stratus and patchy fog may still be nearby in
the afternoon for an early stratus /IFR/ intrusion Saturday evening
and night. Onshore winds 5 to 15 knots during the evening, winds
decreasing to generally light onshore tonight and Saturday morning
then onshore 10 to 20 knots Saturday afternoon.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 933 PM PDT Fri May 9 2025

A fresh to strong northwesterly breeze will persist across much of
the coastal waters through the weekend, with up to near gale force
gusts. Light rain will be possible on Monday as a frontal passage
moves across the region. Moderate seas continue through the end of
the forecast period.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 9 PM PDT Saturday for CAZ516.

PZ...Small Craft Advisory until 3 AM PDT Sunday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt
     Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory from 9 AM Saturday to 3 AM PDT Sunday for
     Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory until 3 AM PDT Saturday for Pigeon Pt to Pt
     Pinos 0-10 nm.

     Small Craft Advisory from 9 AM to 9 PM PDT Saturday for Pigeon
     Pt to Pt Pinos 0-10 nm.

&&

$$

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

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea