Monte Sereno, California Weather Forecast Discussion

470
FXUS66 KMTR 302135
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
235 PM PDT Tue Sep 30 2025
...New SHORT TERM, LONG TERM, MARINE...
.KEY MESSAGES...
Updated at 233 PM PDT Tue Sep 30 2025
- Beneficial rain today into tomorrow
- Warming and drying trend kicks off Friday with the development
   of an inside slider
&&
.SHORT TERM...
Issued at 233 PM PDT Tue Sep 30 2025
(This evening through Thursday)
Isolated rain showers continue across the area - likely with the
help of a surface trough and orographic lift. A storm force low
pressure system off the Pacific Northwest Coast will spawn our
second cold front of the week. Moisture from what was Typhoon
Neoguri has been pulled into this system and as a result, the GEFS
and ECMWF IVT Forecast ensemble mean shows values remaining in
excess of 250 kg/ms for the next 24 hours. Pre-frontal rain showers
are beginning to enter the outer waters - expect these to enter
Sonoma County late this afternoon with increasing coverage and
intensity through the night as the cold front encroaches the Pacific
Coast. The cold front is slow moving and is expected to take near 24
hours to trek across our region, falling apart as it pushes
southeast. Rainfall with this system is expected to be beneficial.
&&
.LONG TERM...
Issued at 233 PM PDT Tue Sep 30 2025
(Friday through next Monday)
Global ensemble clusters continue to suggest that an inside slider-
like pattern will begin to develop by Friday as the upper-level
longwave trough that brought us active weather the past two days
pinches off a low. While there continues to be uncertainty in the
location and strength of the upper-level low (and thus, timing),
this aforementioned feature will develop over Northern California in
a way that will initially preserve onshore flow. By Saturday a
reinforcing upper-level shortwave trough will develop and dig
through Monday - this is when we can expect to see
northerly/offshore flow that will provide further drying. The
rainfall that we have accumulated over the past two days in addition
to what is expected the next two days will be beneficial, but not
fire season ending.
&&
.AVIATION...
(18Z TAFS)
Issued at 1210 PM PDT Tue Sep 30 2025
Light showers linger in the North Bay, but these showers do not look
to affect the terminals. Spotty lower CIGs will be possible, while
most cloud heights remain mid-level through the day. Light showers
build into the North Bay and spread across the region into the night
ahead of the next cold front. The front and main rain band arrive
into the late night and early morning for the North Bay and the SF
Bay. The rain band will lose strength as it pushes south and inland,
becoming weak by the time it reaches the  Monterey Bay on Wednesday
afternoon. Expect some reductions in visibilities within the main
rain band. As the rain band exits, cloud cover and showers become
more scattered.
Vicinity of SFO...Scattered low clouds linger through the day with
more consistent mid-level clouds. Expect moderate southeast winds to
weaken and turn southerly into the night. Prefrontal light showers
arrive in the late night with the main rain band arriving into the
mid morning for Wednesday. The main rain band will offer slightly
increased rain rates resulting in slight reductions in visibilities.
The rain band exits around noon on Wednesday, but lingering light
showers follow in its wake.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Scattered mid-level clouds last through the
afternoon and evening with breezy winds. Expect these winds to
reduce in the evening as MVFR CIGs arrive. These CIGs scatted into
the mid morning as showers approach the terminals.&&
.MARINE...
(Tonight through next Sunday)
Issued at 1210 PM PDT Tue Sep 30 2025
A moderate to rough Northwest swell arrives to the outer waters
Wednesday with up to 12 foot wave heights. A cold front
associated with this storm will also move through Wednesday,
bringing a wind shift from S to NW. This system will bring gusty
conditions and some rain showers as it moves through. The swell
will gradually subside Thursday before a strong NW breeze develops
Friday. This will bring another round of rough seas and small
craft conditions to the coastal waters through Saturday.
&&
.MARINE...
(Tonight through next Sunday)
Issued at 233 PM PDT Tue Sep 30 2025
A moderate to rough Northwest swell arrives to the outer waters
Wednesday with up to 12 foot wave heights. A cold front
associated with this storm will also move through Wednesday,
bringing a wind shift from S to NW. This system will bring gusty
conditions and some rain showers as it moves through. The swell
will gradually subside Thursday before a strong NW breeze develops
Friday. This will bring another round of rough seas and small
craft conditions to the coastal waters through Saturday.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM Wednesday to 9 AM PDT Thursday
     for Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory from 3 PM Wednesday to 9 AM PDT Thursday
     for Pigeon Pt to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Murdock
MARINE...Murdock
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NWS MTR Office Area Forecast Discussion