Guadalupe College, California Weather Forecast Discussion

395
FXUS66 KMTR 161141
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
441 AM PDT Tue Sep 16 2025
...New AVIATION...
.KEY MESSAGES...
Updated at 412 AM PDT Tue Sep 16 2025
- Dense Fog Advisory for portions of the Central Coast until 10AM
- Above normal temperatures with Moderate HeatRisk persists today
   and Wednesday
- Isolated to scattered thunderstorms possible Thursday into
   early Friday
&&
.SHORT TERM...
Issued at 412 AM PDT Tue Sep 16 2025
(Today and tonight)
Areas of dense fog have developed overnight from the San Francisco
Peninsula Coast south through Santa Cruz, Monterey Bay, the Salinas
Valley and the Big Sur Coastline, with a Dense Fog Advisory out
until 10am. Otherwise we`re looking at another day with temperatures
well above normal and widespread moderate HeatRisk, expect daytime
highs today to be slightly higher than yesterday. Remember to remain
hydrated with plenty of water and electrolytes, limit time outdoors
during peak heating if possible, and never leave children or pets
unattended in vehicles.
Keeping with the warm trend, overnight lows into Wednesday morning
will continue to be above normal as well, with some elevated areas
in the Bay Area, East Bay Hills, Diablo Range, and Santa Lucias
remaining in the 70s with poor RH recovery.
&&
.LONG TERM...
Issued at 412 AM PDT Tue Sep 16 2025
(Wednesday through Monday)
Wednesday will be the last day of the three day heat wave, with
temperatures similar to todays highs and widespread Moderate
HeatRisk. A pattern shift for Thursday and Friday into the weekend
will continue to bring cooler temperatures, rainfall chances and
elevated thunderstorm chances. However, there has been a not so
subtle shift in guidance across the board in the most recent
updates. Isolated to scattered thunderstorms remain in the forecast
for now from the Bay Area south through the Central Coast during the
day Thursday into early Friday. The upper level pattern has shifted
quite a bit from Monday afternoons forecast update to this morning.
An unusual synoptic pattern (a double Omega Block across CONUS?),
agreed upon in numerous forms of deterministic guidance has the
remnants of Mario becoming the more dominant feature as it lifts
north into SOCAL. As a result, the bulk of rainfall and
instability has taken a notable shift east and south away from our
forecast area. That doesn`t mean we won`t see any showers or
thunderstorms over the next 72 hours, but confidence is lower than
it was yesterday and the trend appears to be drier. There is time
for the forecast to whiplash back to wetter and more unstable for
our area, especially across the Central Coast. But for now
(including most recent 06Z GFS update, and slower northerly
progression of 06z HRRR), it appears that Mario gets absorbed
inland across SOCAL under the negatively tilted ridge axis from SE
Oregon to southern Arizona. PWATs will still be well above normal
and even if we don`t see any rainfall it will feel muggy. We
often say `check back for updates`, today is definitely one of
those days.
&&
.AVIATION...
(12Z TAFS)
Issued at 440 AM PDT Tue Sep 16 2025
Currently VFR at all terminals with the exception of HAF with dense
fog along the immediate coastline and across much of the waters.
Little change in the overall pattern is expected through the TAF
period as the region remains under the influence of longwave upper-
level ridging; thus, similar forecast for 24 hours from now.
Something that could foil the compressed marine layer sticking
around the coastal terminals of HAF, MRY, and SNS are offshore winds
aloft which would result in downsloping winds/compressional warming;
thus, only moderate confidence on LIFR/IFR conditions returning
tonight.
Vicinity of SFO...Currently VFR with westerly flow. High confidence
in VFR and westerly flow prevailing through the TAF period.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Currently VFR and calm at both terminals.
Dense fog continues to be reported within 10 miles of both terminals
with stratus continuing to expand off the coast, so expect LIFR
conditions to return. Moderate confidence on ceilings on the cusp of
IFR/LIFR returning to the terminals tonight.
&&
.MARINE...
(Today through Sunday)
Issued at 412 AM PDT Tue Sep 16 2025
A gentle to moderate northerly breeze will prevail today,
increasing to become fresh to strong for the northern outer waters
Wednesday and Thursday. Moderate seas will prevail today,
building to become rough for the outer waters Wednesday through
Friday. Isolated thunderstorms are possible Wednesday and
Thursday with isolated rain showers lingering through Saturday.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Dense Fog Advisory until 10 AM PDT this morning for CAZ509-
     528>530.
PZ...Dense Fog Advisory until 10 AM PDT this morning for Mry Bay.
&&
$$
SHORT TERM...JM
LONG TERM....JM
AVIATION...Sarment
MARINE...Sarment
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NWS MTR Office Area Forecast Discussion