Loma Mar, California Weather Forecast Discussion

626
FXUS66 KMTR 301911
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1211 PM PDT Tue Sep 30 2025
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1251 AM PDT Tue Sep 30 2025
- Scattered showers possible along the coast and the higher
   elevations through the day
- Another cold front brings renewed chances for rain tonight into
   Wednesday
- Slight warming and drying trend begins Thursday with offshore
   flow possible this weekend
&&
.SHORT TERM...
Issued at 1251 AM PDT Tue Sep 30 2025
(Today and Wednesday)
The short term forecast is dominated by a pair of cold fronts
stemming from a developing low off the coast of the Alaska Panhandle
and British Columbia, which is expected to pull in moisture from the
remnants of Typhoon Neoguri as it develops in the North Pacific. As
of midnight a band of showers associated with a weak cold front was
located off the coast of Monterey County, coming onshore in western
Santa Cruz and extreme southern San Mateo counties with the band
falling apart beyond the crest of the Santa Cruz Mountains. This
band is expected to continue diminishing as it travels southward
with any rain in the Central Coast limited to the coastal regions.
Any accumulations will be light and generally below a tenth of an
inch. To the north, scattered post-frontal showers linger through
the day across topographically favored locations across the North
Bay and into the Bay Area, again with generally light accumulations
expected through the evening.
A second weak cold front will then approach the region tonight
through Wednesday, bringing a new chance for rainfall. Pre-frontal
showers will begin tonight across the North Bay before the main rain
band comes through the region on Wednesday. Rainfall totals for this
system remain rather similar to the previous forecast. The mountains
of Sonoma and Marin counties should expect 0.5-1" with this system,
with 0.25-0.5" in the North Bay Valleys, 0.1-0.25" in the San Mateo
Peninsula, the western part of Santa Cruz County, and the East Bay
west of the Berkeley Hills and north of Oakland, and less than 0.1"
in the interior East Bay, South Bay, and the Central Coast.
High temperatures today remain around 5 to 10 degrees below
seasonal averages, with the inland valleys reaching the lower to
middle 70s and the coastal regions seeing the lower 60s to the
lower 70s.
&&
.LONG TERM...
Issued at 1251 AM PDT Tue Sep 30 2025
(Thursday through Monday)
Upper level troughing remains off the coast through Thursday. By
Friday, the trough moves inland with an upper level ridge building
in the eastern Pacific, with a possible inside slider developing
over the weekend. The ensemble model clusters continue to show
significant uncertainty in the location and strength of a potential
inside slider. This, in turn, keeps the uncertainty over the
potential impacts rather high. A weaker inside slider, or one that
develops closer to the northern part of California, may keep onshore
flow in place over the region, while a stronger inside slider that
develops over Nevada may turn the winds into a northerly/offshore
pattern. Wetting rains across the North Bay, and to a lesser extent,
the rest of the Bay Area, will likely alleviate fire weather
concerns, but not eliminate them.
Beyond the weekend, ensemble model clusters continue to hint at some
form of troughing persisting over the western United States through
the early part of next week. While conditions are expected to remain
on the drier side, the troughing will limit the expected warming,
perhaps leaving temperatures close to the seasonal averages to start
the next work week (middle 70s to lower 80s in the inland
valleys, middle 60s to lower 70s along the coast).
&&
.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.
&&
.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...DialH
LONG TERM....DialH
AVIATION...Murdock
MARINE...Murdock
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NWS MTR Office Area Forecast Discussion