Spreckels, California Weather Forecast Discussion

707
FXUS66 KMTR 220009 AAA
AFDMTR
Area Forecast Discussion...UPDATED
National Weather Service San Francisco CA
509 PM PDT Sun Sep 21 2025
...New AVIATION...
.KEY MESSAGES...
Updated at 136 PM PDT Sun Sep 21 2025
- Warming trend Monday and into Tuesday, with Moderate HeatRisk
   across the interior
- Weak offshore flow Monday through Tuesday in the higher terrain
- Rain showers and isolated thunderstorm chances return Tuesday and
   lingering through midweek
&&
.SHORT TERM...
Issued at 136 PM PDT Sun Sep 21 2025
(This evening through Monday)
Stratus is currently retreating to the coast this afternoon with
mostly sunny skies across inland areas. As such, temperatures will
warm into the mid 80s to lower 90s across the interior, upper 70s to
lower 80s around the San Fransico Bayshore and Santa Cruz region,
while mid 60s to lower 70s will prevail near the coast. Meanwhile,
cumulus clouds are developing this afternoon across the higher
elevations.
Tonight, expecting much less in the way of stratus as the airmass
aloft continues to warm and with light offshore flow in the higher
terrain across the Bay Area and Central Coast. This will lead to a
quicker warm up on Monday with temperatures reaching 5-10 degrees F
above seasonal averages (warmer than today) with warming 850 MB
temperatures. Offshore winds will continue into Tuesday afternoon
across the higher terrain, yet are not forecast to be all that
strong. This will result in elevated fire weather concerns as
minimum relative humidity values will be between 15-25% in these
higher elevations.
&&
.LONG TERM...
Issued at 136 PM PDT Sun Sep 21 2025
(Monday night through next Saturday)
Tuesday will likely be the warmest day of the week as mid/upper
level clouds forecast to approach the Central Coast have been
delayed by about 6-12 hours. Thus, afternoon temperatures are
forecast to reach the upper 80s to upper 90s across the interior,
upper 70s to lower 80s for San Fransico (away from the Pacific
Ocean) and around the Santa Cruz region, low 80s to low 90s around
the San Francisco Bayshore, and upper 60s to upper 70s near the
coast. This will result in Moderate HeatRisk across most inland
areas on Tuesday.
Sub-tropical and/or monsoonal moisture will be advected northward as
a cut-off mid/upper level low pressure nears the Central Coast from
the south, brining the potential for rain showers and isolated
thunderstorms to the Central Coast on Tuesday afternoon. With PWAT
values between 1.00"-1.40" and MUCAPE values between 100-300 J/kg
expected, the threat for dry lightning will be very limited. This is
also supported by the CAMs (Convection-Allowing Models). The
potential for rain showers and isolated thunderstorms will extend
northward into the North Bay by Wednesday morning and may linger
into Wednesday night before the upper level feature shifts inland.
Dry conditions are anticipated by Thursday afternoon in wake of the
exiting cut-off low. A gradual cooling trend, to near seasonal
averages, is expected late in the upcoming week and into the
following weekend as troughing lingers over the West Coast. Be sure
to keep up to date on the latest forecast information as we near
this upcoming pattern shift.
&&
.AVIATION...
(00Z TAFS)
Issued at 507 PM PDT Sun Sep 21 2025
Currently VFR, except at KMRY and KHAF. Generally a medium
confidence ceiling/visibility forecast over the next 24 hours.
The overall wind pattern will largely discourage the development
of MVFR/IFR stratus, with the exception being across terminals
immediately along the coast (specifically at KHAF). However, there
are some indications that very intermittent periods of non-VFR
cigs and visibility may develop at some at KAPC, KSTS, and KOAK.
For now, will advertise VFR, but insertion of ceilings may be
needed in future updates. Any sites that become inundated with
poor cigs/visibility should become VFR after 18Z Monday.
Vicinity of SFO...Currently VFR and VFR is likely to be the
predominant flight category through this TAF set. However, there`s
around a 20% chance that MVFR cigs may slip through the San Bruno
Gap just before daybreak Monday. For now, will advertise a FEW to
SCT deck of clouds, which could still impact the morning push.
Should MVFR develop, VFR will return late morning/early afternoon.
SFO Bridge Approach...VFR, however, FEW to SCT clouds may be
impactful during the morning push with higher chances for cigs at
the terminal itself.
Monterey Bay Terminals...IFR stratus continues to seep into the
Salinas Valley and over the Monterey peninsula. Current
indications in high-resolution data suggest that an eddy will
develop across the Monterey Bay. Depending exactly on where this
setups up could influence stratus. Current thinking is that it`ll
be largely beneficial to keep stratus in place for most of the TAF
period, but intermittent periods of VFR cannot be discounted,
especially if the eddy sinks southward toward the peninsula and
pulls in a little more dry air. VFR is anticipate later morning
Monday.
&&
.MARINE...
(Tonight through next Friday)
Issued at 333 PM PDT Sun Sep 21 2025
Locally hazardous conditions north of Point Reyes this evening
through early Monday due to stronger winds and steep wind waves.
Elsewhere, light to moderate northerly flow will persist into next
week. Northwesterly swell will build through Monday. There is a
low chance for showers and embedded thunderstorms Tuesday into
Wednesday across the southernmost waters. Winds decrease and seas
abate across the coastal waters Tuesday through late week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt
     Reyes 0-10 nm.
Small Craft Advisory until 3 PM PDT Monday for Pt Arena to Pt
     Reyes 10-60 NM.
&&
$$
SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Bain
MARINE...MM
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NWS MTR Office Area Forecast Discussion