FXUS66 KMTR 191124 RRA
AFDMTR
Area Forecast Discussion...DELAYED
National Weather Service San Francisco CA
424 AM PDT Sat Sep 19 2026
...New AVIATION, MARINE, FIRE WEATHER...
.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...
(12Z TAFS)
Issued at 418 AM PDT Sat Sep 19 2026
IFR and low-end MVFR stratus are developing across the inland
valleys with some further expansion possible before sunrise. Stratus
will retreat back to the coastal regions through the morning with a
gentle to moderate onshore flow through the afternoon and evening
hours. Stratus returns to the terminals this evening and overnight,
with moderate confidence on timing and ceilings heights.
Vicinity of SFO... IFR to low-end MVFR stratus persists through
around 18Z with moderate to strong northwest winds developing in
the afternoon and evening hours. MVFR-IFR stratus returns in the
evening as the winds turn light, with clearing not expected
through late SUnday morning close to the end of the TAF period.
SFO Bridge Approach... Similar to SFO.
Monterey Bay Terminals... IFR-LIFR ceilings persist through the late
morning hours around 18Z. Gentle to moderate northwest winds develop
in the afternoon and evening hours, with IFR-LIFR ceilings returning
in the evening, although confidence in stratus development time is
moderate.
&&
.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...DialH
MARINE...DialH
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Prepared by Boulder-Creek.com Weather at: Sat Sep 19 06:30:03 PDT 2026
From the National Weather Service
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