Moffett Field, California Weather Forecast Discussion

147
FXUS66 KMTR 200457
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
957 PM PDT Fri Sep 19 2025
...New AVIATION, MARINE...
.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...
(06Z TAFS)
Issued at 957 PM PDT Fri Sep 19 2025
Increasing confidence in potential for MVFR-IFR CIGs across the
region tonight. MVFR CIGs are starting to build in and are expected
to lower to IFR overnight. There is some potential for coastal sites
(HAF, MRY, SNS) to see fog early tomorrow morning beginning around
12Z but confidence was too low to include in the TAF. Stratus looks
to clear by mid to late morning with stratus returning late tomorrow
evening along the coastline.
Vicinity of SFO...Moderate confidence that MVFR-IFR CIGs will build
in overnight. Highest confidence that MVFR CIGs will build in with
ensembles suggesting ceilings will lower and become IFR overnight.
Stratus clears by mid to late morning with guidance indicating some
potential for stratus to come back towards the end of the TAF
period. Northwest winds strengthen during the afternoon/evening with
gusts peaking around 23 knots.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...MVFR CIGs lowering to IFR overnight.
Visibilities are expected to decrease overnight but there is some
spread as to how much they will decrease. Some guidance shows fog at
MRY and SFO while others keep visibilities around 2SM to 4SM. For
the TAFs, leaned slightly optimistic given the relatively higher
marine layer and kept visibilities around 4SM. Stratus and fog
should clear by late morning with stratus looking to return early
tomorrow evening.
&&
.MARINE...
(Tonight through next Thursday)
Issued at 957 PM PDT Fri Sep 19 2025
A light to gentle breeze prevails across the coastal waters
through Saturday morning. Saturday afternoon the coastal jet
strengthens, becoming locally fresh to strong, off the Big Sur
Coast and Santa Cruz Coastline. Saturday night into early next
week, winds increase to fresh to strong across the coastal waters
with locally near gale force gusts across the northern outer
waters. Winds decrease to moderate to fresh across the coastal
waters Tuesday through late week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM Saturday to 3 AM PDT Sunday for
     Pt Pinos to Pt Piedras Blancas 0-10 nm.
&&
$$
SHORT TERM...MM
LONG TERM....MM
AVIATION...Kennedy
MARINE...Kennedy
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NWS MTR Office Area Forecast Discussion