146
FXUS66 KMTR 191812
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1112 AM PDT Sat Sep 19 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 1202 AM PDT Sat Sep 19 2026

 - Warming trend continues today

 - Brief cooling on Sunday into Monday

 - Warming trend resumes on Tuesday

&&

.SHORT TERM...
Issued at 1202 AM PDT Sat Sep 19 2026
(Today and tonight)

Marine layer stratus has developed along the coast and is flowing
into the SF Bay Area and Monterey Bay regions. Some patches of
radiational stratus have also developed inland. Further expansion
is expected across most of the valleys tonight before stratus
retreats to the immediate coast after sunrise.

The weather pattern places an upper level ridge over the West Coast
today, allowing for the warming trend over the last couple of days
to continue. The upper level trough that brought us cool
temperatures and widespread clouds is crawling over southern Idaho,
and as it does, the pressure gradients will start to support some
northeasterly offshore flow in the higher elevations of the North
Bay and East Bay, with gusts to 20 to 30 mph possible through the
morning hours. At midnight, the SFO-WMC gradient has turned negative
at -1.3 mb, and will peak around  -2 or -3 mb during the 6-9 AM
timeframe. High temperatures in the inland valleys will reach the
80s to the lower 90s, while the Bays reach the upper 60s to the
lower 80s and the Pacific coast hovers in the lower to middle 60s.
Afternoon breezes should be similar to those seen yesterday with
gusts of 20 to 30 miles per hour along the coast, through favored
gaps and passes, and within the Salinas Valley.

&&

.LONG TERM...
Issued at 1202 AM PDT Sat Sep 19 2026
(Sunday through Friday)

On Sunday, a cutoff low heads into the state and interrupts the
warming trend, cooling the inland valleys by around 5 to 10 degrees
for Sunday and Monday such that highs will be in the middle 70s to
the lower 80s, rising to the middle 80s up to the lower 90s in the
interior parts of the North Bay and Central Coast, with the Bays see
highs in the middle 60s to the middle 70s. By Monday morning, the
core of the low should set up right over the Central Coast, giving
us a slight chance for drizzle.

Upper level ridging returns by Tuesday, and a warming trend resumes
with the current forecast showing Moderate HeatRisk returning to a
fair swath of the interior by Wednesday and Thursday, most notably
the interior East and South Bays and the Santa Lucia range. This
would correspond to a moderate risk for heat related illnesses
within sensitive populations (children, the elderly, pregnant women,
people with chronic diseases, and people who work or live outdoors
without adequate cooling or hydration). Inland highs for Wednesday
and Thursday are expected to be in the 90s, which is supported by
ensemble models continuing to show that 850 mb temperatures above
20C (or temperatures around 1500 ft above sea level above 68F) are
likely to nearly certain for those two days, with an average around
21-22C, close to the 90th percentile for this time of year. This is
a shade cooler than the last forecast update, so we will be watching
how the situation evolves as we go through the weekend.

&&

.AVIATION...
(18Z TAFS)
Issued at 1112 AM PDT Sat Sep 19 2026

Marine layer around 1000 feet with low cigs rapidly retreating
towards the coast. Expect all terminals to be VFR by 19z except
KMRY and KHAF. Low cloud deck to surge back inland tonight as next
shortwave trough approaches with slight deepening of the marine
layer overnight into Sunday.

Vicinity of SFO...Ceilings have cleared with west winds this
afternoon/evening. Low cigs to return after 05z tonight and
lasting at least through 18z Sunday.

SFO Bridge Approach...Approach is clear and will stay that way at
least through 06z tonight.

Monterey Bay Terminals...Low cigs to pull back to the coast by
19z. Low cigs may linger near KMRY for much of the day and then
spread back inland by 02z and down the Salinas Valley.

&&

.MARINE...
(Today through Thursday)
Issued at 418 AM PDT Sat Sep 19 2026

Moderate to fresh northwest winds persist through the weekend.
Strong gusts up to 30 kt are possible across the northern coastal
waters, the Big Sur coastal jet region, and Monterey Bay through
the day. Winds briefly diminish across the southern coastal
waters this morning, but increase again to fresh by the
afternoon. Slight to moderate wind driven seas prevail this
weekend and steadily build to rough early next week.

&&

.FIRE WEATHER...
Issued at 418 AM PDT Sat Sep 19 2026

The marine layer has compressed to around 1000-1500 feet, with
relative humidity values of 30-50 percent above the base of the
inversion. Weak offshore flow is possible in the higher
elevations this morning especially in the higher elevations of the
North and East Bay, helping to reinforce some nocturnal drying
that has been observed so far this morning. Onshore winds should
prevail by the afternoon. Cooler conditions and a deeper marine
layer are expected as a cutoff low comes over the region on Sunday
and Monday.

DialH

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 AM PDT Sunday for Pt Arena to Pt
     Reyes 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Sunday
     for Pigeon Pt to Pt Pinos 0-10 nm.

     Small Craft Advisory from 3 PM to 9 PM PDT Sunday for Pigeon Pt
     to Pt Pinos 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Monday
     for Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 AM PDT Monday for Pt Arena to Pt
     Reyes 10-60 NM.

     Small Craft Advisory until 3 AM PDT Monday for Pigeon Pt to Pt
     Pinos 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...RW
MARINE...RW

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