Dillon Beach, California Weather Forecast Discussion

611
FXUS66 KMTR 050856
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
156 AM PDT Sun Oct 5 2025
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 1250 AM PDT Sun Oct 5 2025
- Warm and dry weather through mid-week.
- Disturbed weather returns late week.
&&
.SHORT TERM...
Issued at 1250 AM PDT Sun Oct 5 2025
(Today and tonight)
The SFO-WMC gradient is -3.9 mb and strengthening. N to NE winds
prevail above the boundary layer. This offshore flow is bringing
drier air to the cwa. The marine layer is less than 1,000 feet
deep in the North Bay, and around 1,500 feet deep throughout the
Central Coast. The driest air today was actually measured on the
western slopes of Mt. Tam with an minimum RH of 23% due to a
combination of a drier air mass and adiabatic warming from the
downslope flow. With a deeper marine layer further south, the dry
air isn`t quite making it all the way to the coast south of the
Golden Gate, where there is still a blanket of marine layer
coastal stratus. Today will be a couple degrees warmer and
slightly drier than yesterday as the offshore flow becomes more
widespread and a bit stronger. Bottom line, expect another nice
day with comfortable temperatures and plenty of sunshine.
&&
.LONG TERM...
Issued at 1250 AM PDT Sun Oct 5 2025
(Monday through Saturday)
The offshore gradient between troughing over the coast and high
pressure over the Intermountain West will continue to strengthen,
eventually bottoming out around -9 mb Monday morning. That`s
not quite reaching Diablo wind territory (-12 mb, -15 mb for
strong event). The 06Z HRRR shows the strongest 925 mb winds over
NE Napa County reaching 25 knots from the NE Monday morning. While
weaker, the entire cwa will have some easterly component to the
925 mb winds by this point. The marine layer will also compress
and start to entrain some of this dry air Monday morning. High
pressure over the Rockies will hold through Tuesday, but the
troughing over California will weaken, relaxing the gradient and
calming the offshore winds. By Wednesday the surface high over the
Rockies will also start to weaken and move east into the Plains,
further reducing the offshore gradient, which will likely flip
back to neutral or onshore by midday.
The forecast becomes chaotic and highly uncertain late next week.
Ensemble clusters agree that a mid level deep trough or cut-off
low will move offshore of the Pacific Northwest by Thursday.
That`s where the agreement ends. Some solutions bring the low
onshore, dragging a pretty standard cold front and some light to
moderate rain across the cwa by the weekend. Others have the low
stall or even retrograde back west. Another complicating factor
is Tropical Storm Priscilla in the Eastern Pacific. This storm is
currently quite large and will very likely strengthen into a
hurricane by Monday morning as it drifts slowly NW parallel to the
west coast of Mexico. This system will begin to decay as it
encounters much colder water and a drier air mass by Wednesday.
However, the forward speed will increase and the residual moisture
plume will reach Southern California as early as Thursday. The
biggest question in the forecast is if this moisture will reach
the Bay Area before the cold front arrives and stops its forward
progress. It it does, the front will have a very juicy atmosphere
to lift, potentially bringing up to an inch or rain to parts of
the Bay Area. If it doesn`t, the offshore winds all week will
leave a drier than normal air mass, severely limiting rain
potential. To demonstrate the uncertainty, the NBM 72 hour
precipitation spread (10th-90th percentile) paints a stark
contrast. The wet scenario would bring 1.7" of rain to NW Sonoma
County through the weekend, while the dry scenario wouldn`t bring
a drop. Those outcomes are both equally likely at the moment, so
don`t put too much faith in the forecast details. All we can say
now is the next chance for rain arrives late next week, but we
can`t yet say how much will fall.
&&
.AVIATION...
(06Z TAFS)
Issued at 934 PM PDT Sat Oct 4 2025
Coastal low clouds /MVFR-IFR/ will continue to develop, including
patchy valley fog /IFR-LIFR/ later tonight and Sunday morning.
Winds becoming light and variable to light offshore winds tonight
and Sunday except becoming locally onshore Sunday afternoon.
Vicinity of SFO...VFR. West to southwest wind 5 knots tonight then
light northeast-east Sunday to temporarily onshore 10 knots Sunday
afternoon.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...MVFR-IFR ceilings developing tonight and
Sunday morning. West to northwest winds 5 to 10 knots, becoming
light southeast tonight and Sunday morning. Winds becoming west to
northwest 5 to 10 knots mainly Sunday afternoon.
&&
.MARINE...
(Tonight through next Friday)
Issued at 822 PM PDT Sat Oct 4 2025
Fresh breezes continue across the waters, with a few gale force
gusts for the offshore waters north of Pigeon Point. Winds will
gradually subside through the weekend. This will translate to
steep and rough seas up to 10 feet resulting in hazardous boating
conditions. Winds continue to ease into next week with light winds
persisting across the waters through the work week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT early this morning for
     Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-
     Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena
     to Pt Reyes 10-60 NM.
Small Craft Advisory until 9 AM PDT this morning for Pigeon Pt
     to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Canepa
MARINE...Canepa
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NWS MTR Office Area Forecast Discussion