Robles Del Rio, California Weather Forecast Discussion

091
FXUS66 KMTR 200249
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
749 PM PDT Fri Sep 19 2025
...New UPDATE...
.KEY MESSAGES...
Updated at 133 PM PDT Fri Sep 19 2025
- Showers with isolated thunderstorms today
- Cooler temperatures today, with a weekend warm up
- Weak offshore flow on Monday
- Rainfall chances increase again early next week
&&
.UPDATE...
Issued at 741 PM PDT Fri Sep 19 2025
The little rain shower activity/thunderstorm threat that we had
today will wane as the sun sets. No sites have reported measurable
precipitation (0.01" or greater) within the last six hours and
only two sites have reported 0.01" in the last 12 hours. KMUX
remains in VCP 215 to monitor rain showers just to the north of
our North Bay Counties, but I don`t expect anything to come of
them for us. Our attention tonight will turn towards the
possibility of fog (potentially dense) developing along the coast
in the wake of recent low-level moisture. No changes to the
forecast needed at this time. Your weather nugget of the day: the
September 20th 00Z balloon recorded a 1.30 inches precipitable
water value, this is the second highest for this date and time
with the record of 1.37 inches dating back to 1984.
Sarment
&&
.SHORT TERM...
Issued at 113 PM PDT Fri Sep 19 2025
(This evening through Saturday)
A lot to be seen on the satellite imagery this afternoon: morning
stratus has eroded back to the coastal waters, mid-upper level
comma-esque cloud field remains over the region with the Bay Area
under sunshine, and building cu field over the East Bay and
Central Coast terrain. Additionally, radar remains in precip mode
due to a few isolated showers sweeping through the northern North
Bay region.
While the chance for precip has decreased dramatically compared to
yesterday, lingering moisture and daytime heating may result in a
few popcorn showers over the East Bay and Central Coast terrain.
Highest likelihood would be interior San Benito/S Gabilan Range.
Once the sunset, convective potential really decreases. Bigger
impact tonight will be the marine layer and chance for patchy
dense fog along the coast and inland valleys.
Warmer and drier conditions are expected on Saturday. A few
afternoon cu will be possible, but not expecting any precip at
this time.
&&
.LONG TERM...
Issued at 138 PM PDT Fri Sep 19 2025
(Saturday night through next Thursday)
The longwave pattern shows the meandering cut-off low to the west
slowly drifting southward Sunday into Monday. The southward drift
is in response to a passing trough to the north. Resulting
weather for the region will be subtle warming trend continues with
max temps reaching the 60s and 70s coast and 80s to near 90
interior. Additional warming is expected on Monday.
Monday into Tuesday the upper trough continues into the N Plains
with high pressure building over the PacNW. At the surface, high
pressure will initially build over NorCal/OR/WA before shifting
eastward. The eastward shift will set the stage for some pushes
of offshore flow Monday/Tuesday. Long range pressure gradients
are showing moderate strength at best and most realized over the
North Bay and East Bay higher terrain.
The pesky upper low that drifted southward wants to return by
Tuesday into Wednesday and this time it brings some higher PWAT
air with it. Previous model runs had a more northern track of
this feature, but today`s runs keep the focus farther south and
into SoCal. Current forecast still holds the northern track with
rain, low chc thunderstorms, Tuesday and Wednesday. However, if
the trend continues the forecast will shift drier.
&&
.AVIATION...
(00Z TAFS)
Issued at 445 PM PDT Fri Sep 19 2025
MVFR-IFR CIGs expected overnight. The marine layer is currently
around 1500-2000 ft and expected to remain around that depth again
tonight, bringing widespread stratus to the region. Adjusted the
TAFs to show more MVFR CIGs across the interior and MVFR-IFR CIGs
along the coastline. There is some potential for fog tonight along
the coast and at STS but confidence is on the lower end given the
relatively high depth of the marine layer. Conditions improve by mid
to late morning with most sites clearing by 17-18Z.
Vicinity of SFO...MVFR conditions expected at SFO overnight with
some potential for IFR CIGs after 12Z. Any IFR CIGs that do develop
will be temporary in nature with MVFR the prevailing conditions.
Stratus clears out by late morning with VFR through the rest of the
TAF period. Winds strengthen during the afternoon/evening with gusts
to around 23 knots expected.
SFO Bridge Approach...Stratus filling in over the SF Bay may result
in loss of VAPs from the SFO Bridge Approach. Timing is similar to
that in the SFO TAF (approximately from 08Z to 18Z).
Monterey Bay Terminals...Mix of MVFR and IFR conditions overnight.
Highest confidence in MVFR CIGs at both airports with model guidance
showing potential for IFR-LIFR overnight. Leaned more towards IFR
CIGs tonight over LIFR considering that the marine layer is around
1500-2000 ft which would support ceiling bases being higher.
Clearing is anticipated by mid to late morning with breezy onshore
winds during the afternoon and evening.
&&
.MARINE...
(Tonight through next Wednesday)
Issued at 445 PM PDT Fri Sep 19 2025
Light winds will prevail across the coastal waters tonight through
Saturday. From Saturday night to early week, winds over the outer
coastal waters will become breezy from the northwest. Beginning
Monday and continuing Tuesday surface high pressure will build
over the Great Basin. This will result in a general decrease in
winds over the coastal waters possibly including light offshore
wind development nearest the coastline and the San Francisco Bay.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
SHORT TERM...MM
LONG TERM....MM
AVIATION...Kennedy
MARINE...Canepa
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NWS MTR Office Area Forecast Discussion