Graton, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

757
FXUS66 KMTR 222226
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
326 PM PDT Mon Sep 22 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 138 PM PDT Mon Sep 22 2025

 - Warming trend continues through Tuesday, areas of Moderate and
   Major HeatRisk on Tuesday

 - Weak offshore flow through Tuesday in the higher terrain

 - Rain showers and isolated thunderstorm chances return Tuesday
   night and lingering through midweek

&&

.SHORT TERM...
Issued at 138 PM PDT Mon Sep 22 2025
(This evening through Tuesday)

Another very warm afternoon expected away from the immediate
coastline with Moderate HeatRisk across the interior where
temperatures warm into the low to mid 90s. Temperatures will begin
to cool after sunset this evening and lower into the mid 50s to
lower 60s across most coastal and valley locations. However, the
higher terrain will remain warm with temperatures only dropping into
the mid 60s to lower 70s overnight. Offshore winds are likely in the
peaks and ridges across much of the region through Tuesday afternoon
with minimum relative humidity values between 15-25%. However, winds
speeds are not forecast to be greater than 15 mph with gusts up to
about 25 mph in the peaks and ridges. Expecting low clouds and/or
fog once again near the coast and around the Monterey Bay region as
the marine layer is forecast to be anywhere between 250-750 feet in
depth.

Tuesday is expected to be the warmest day of the week as
temperatures soar into the mid-to-upper 90s and may approach 100
degrees F across the warmest interior spots across the region.
Downtown San Francisco has about an 80% chance of exceeding 85
degrees F and a 10% chance of exceeding 90 degrees F. This is when
more widespread Moderate HeatRisk spread to coastal locations with
pockets of Major HeatRisk across the East Bay Valleys and portions
of Santa Clara Valley.

&&

.LONG TERM...
Issued at 138 PM PDT Mon Sep 22 2025
(Tuesday night through next Sunday)

The much advertised sub-tropcial/monsoonal moisture has once again
been delayed as by 6-12 hours as the cut-off mid/upper level low
pressure lingers off of the southern California coast. As this
feature lifts northward toward the Central Coast on Tuesday evening
and into Wednesday, it will advect PWAT values between 1.00"-1.40"
northward across the Central Coast and then by Wednesday afternoon
and evening across the Bay Area and North Bay. The greatest
potential for thunderstorms remains across the Central Coast where
MUCAPE values range between 100-400 J/kg.

The potential for rain showers and isolated thunderstorms will
extend northward into the North Bay by Wednesday afternoon and may
linger into early Thursday morning before the upper level feature
shifts inland and then meanders across or just off of the southern
California coast.

There is also the potential for stronger wind/wind gusts in the
favored gaps, passes, and in the higher terrain from Wednesday
morning into Thursday morning depending exactly where the cut-off
low pressure moves inland. Wind gusts could exceed 45 mph in these
areas if the cut-off low moves inland over the Central Coast as
currently expected.

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 week and the upcoming 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 324 PM PDT Mon Sep 22 2025

Currently VFR at all terminals with very little low stratus clouds
off the coast. Little change in the forecast over the next 24 hours
will yield similar conditions as to what happened in the previous
24 hours; thus, moderate confidence in LIFR ceilings returning to
HAF, MRY, and SNS with the rest of the terminals remaining VFR.
Winds will be light and likely variable overnight, generally
having an offshore component. High clouds will lower through the
TAF period with rain showers likely into the next TAF cycle.

Vicinity of SFO...Currently VFR with northwesterly flow. High
confidence in VFR through the TAF period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently VFR with northwesterly flow at
both terminals. Moderate confidence in LIFR ceilings returning to
both terminals tonight with VFR by late-morning.

&&

.MARINE...
(Tonight through next Saturday)
Issued at 324 PM PDT Mon Sep 22 2025

Moderate west to northwest winds continue through midweek.
Showers and embedded thunderstorms are possible over the coastal
waters Tuesday night through late Wednesday as a cut-off low
approaches from the south. Erratic, gusty winds, locally heavy
rainfall, and lightning are possible if mariners encounter a
thunderstorm. Winds strengthen to fresh to strong and waves build
to 10 to 13 feet Thursday, remaining elevated through the
weekend, as the cut-off low moves into Calif

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Sarment
MARINE...Kennedy

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