Royal Oaks, California Weather Forecast Discussion

334
FXUS66 KMTR 010455
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
955 PM PDT Tue Sep 30 2025
...New AVIATION, 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
&&
.UPDATE...
Issued at 738 PM PDT Tue Sep 30 2025
Rainfall coverage and intensity has picked up this evening as the
cold front discussed below inches closer to the coast. Latest
surface analysis puts the cold front just entering our northern
outer waters or approx 60 miles west of the North Bay. As for
moisture in the atmosphere, the KOAK 00Z sounding measured a
1.11" PWAT, which is a daily record. Despite the ample moisture,
forcing thus far has been lack luster and rainfall amounts as
well. Since roughly 2 PM this afternoon less than 0.05" for the
North Bay. While we still have moisture streaming in and the front
hasn`t pushed all the way through yet, lastest trends are not
looking good for precip totals. At this rate, we`ll come in below
the forecast. We`ll continue to monitor this trend and update is
needed. Otherwise, no update needed as over sensible weather is
on track with precip moving through the region.
&&
.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...
(06Z TAFS)
Issued at 954 PM PDT Tue Sep 30 2025
A mix of stratus offshore of the Central Coast and showers to the
north over the Bay Area are visibile on satellite/radar. Shower
activity is expected to spread north to south overnight and reach
the Central Coast by tomorrow afternoon. If a shower passes directly
over an airport temporary reductions in visibility and lower ceiling
heights may be possible. Low to moderate confidence that CIGs will
stay above 3000 ft at most airports tonight (excluding HAF, MRY, and
SNS) with the most recent guidance backing off of MVFR CIGs across
the Bay Area tonight. Winds initially will be out of the south but
are expected to become more west to northwest throughout the day.
Initial guidance is indicating stratus for HAF, MRY, and SNS by late
tomorrow evening but confidence is low at this time.
Vicinity of SFO...VFR through the TAF period with some potential for
MVFR CIGs to develop tomorrow morning as showers move over the Bay
Area. Confidence is moderate that CIGs will remain VFR / above 3000
ft through the entire TAF period with recent guidance having backed
off of MVFR CIGs at SFO. Initial southerly winds will shift more
west to northwest by the end of the TAF period with gusts up to 21
knots possible during the afternoon/evening.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...MVFR tonight becoming VFR by late tomorrow
morning. Current showers are located well to the north of MRY and
SNS with satellite showing stratus developing offshore of the
Monterey Peninsula. MVFR-IFR stratus is expected at both SNS and MRY
tonight and is expected to clear by mid to late tomorrow morning.
Shower potential increases by the afternoon/evening hours with low
to moderate confidence that showers will directly impact either
terminal. Winds will initially be more southerly and shift to more
west to northwest by the end of the TAF period.
&&
.MARINE...
(Tonight through next Monday)
Issued at 954 PM PDT Tue Sep 30 2025
An upper level trough and associated surface cold front will
result  in scattered showers across the coastal waters now through
late  Wednesday. A moderate to rough northwest swell associated
with this  system arrives Wednesday night and will bring waves
between 10 to 11  feet across the outer waters. Wave heights will
diminish below 10  feet Thursday into Friday before building again
late weekend into  next week. Winds are expected to strengthen to
fresh to strong on  Friday which will result in a continuation of
rough seas and  hazardous conditions for small crafts into the
weekend.
&&
.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...Kennedy
MARINE...Kennedy
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NWS MTR Office Area Forecast Discussion