667
FXUS66 KMTR 131228
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
528 AM PDT Sun Jul 13 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 1229 AM PDT Sun Jul 13 2025

 - Temperatures near to slightly below seasonal averages with a
   more noticeable cooling trend beginning Tuesday.

 - Localized elevated fire weather threat continues across the
   higher elevations.

&&

.SHORT TERM...
Issued at 1229 AM PDT Sun Jul 13 2025
(Today and tonight)

Satellite imagery shows the stratus layer blooming inland into the
Sonoma County valleys, the East Bay, Silicon Valley, the Monterey
Bay region, and the Salinas Valley. Profilers from Bodega Bay, Fort
Ord, and Point Sur are depicting a marine layer around 1500 ft deep,
conducive to extensive inland stratus development through the rest
of the night, before the clouds retreat to the immediate coast
during the morning. The marine layer should compress somewhat
through the day with a weak ridge axis slowly retrograding across
the state, but some inland stratus is still expected tonight.
Morning lows range in the middle to upper 50s for the lower
elevations, to the 60s and lower 70s in the higher elevations. High
temperatures reach the 80s into the lower 90s inland, with highs in
the upper 90s or near 100 expected at the southern reaches of
Monterey and Salinas and places in the far interior Bay Area
adjacent to the Central Valley. Elsewhere, the Bayshore should see
highs in the 70s and lower 80s, downtown San Francisco should rise
to near 66, and the Pacific Coast should see highs in the upper 50s
to lower 60s. Onshore winds will develop in the afternoon and
evening with gusts as high as 25 mph through favored gaps and
passes and within the Salinas Valley.

Localized elevated fire weather threat persists across areas above
and inland of the marine layer`s influence. The combination of dry
daytime humidities of around 20-35%, poor overnight recoveries of 25-
40%, and localized gusts to 25 mph will be the main factors behind
the elevated threat. However, the winds will remain onshore, leading
to the fire weather threat being diurnally driven, especially in the
foothills where lighter winds and good overnight recoveries are
expected each night.

&&

.LONG TERM...
Issued at 1229 AM PDT Sun Jul 13 2025
(Monday through Saturday)

Expect Monday to feature similar conditions to today. Late on
Monday, a shortwave trough, or perhaps a weak cutoff low, develops
into the Pacific Northwest, pushing the ridge axis towards the west
and north and causing a noticeable cooling trend to begin on Tuesday
and lasting for at least the following two days. High temperatures
drop into the middle 70s to middle 80s inland and the upper 60s to
the middle 70s along the Bayshore, with the coast remaining rather
stable at the upper 50s to lower 60s.

Towards the end of the forecast period, the forecast becomes a
little more uncertain. Ensemble model cluster analysis points to
weak ridging (i.e. warmer temperatures) and weak troughing (i.e.
cooler temperatures) by Friday, with the differences compounding
through the upcoming weekend into the early part of the following
week, when a significant ridge and a significant trough are possible
across the western United States. With the two scenarios having
nearly equal probabilities, there is not enough confidence at this
time to deviate from the default NBM forecast, which depicts a
gradual warming trend heading into the upcoming weekend. CPC
outlooks suggest a slight lean towards temperatures above seasonal
averages in the 8-14 day period (July 20-26).

&&

.AVIATION...
(12Z TAFS)
Issued at 528 AM PDT Sun Jul 13 2025

The forecast is on repeat, which means after this morning`s surge of
stratus, fog, and patchy drizzle clouds should retreat back to the
coast leading to VFR conditions for the afternoon. Another night of
IFR to LIFR cigs is expected as the marine layer surges inland this
evening and into the overnight hours.

Vicinity of SFO...Satellite shows stratus blanking the San Francisco
Bay this morning. Guidance shows stratus potentially starting to
erode between 14-17Z with stratus likely hugging the west side of the
San Mateo county throughout the day. This may lead to low clouds
meandering around the San Bruno approach, though VFR conditions
should be expected east of there and around the Bay. West to west-
northwest winds look to pick up with gusts up to 20-25kt beginning
late this morning and continuing through the evening. Winds should
decrease to less than 15kt before 6Z, with stratus likely starting
to slink in around that time as well. Another night of low cigs is
expected.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus is socked in around the Monterey
Bay and associated valleys, with webcams, weather stations, and
manual observations showing reduced fog or even drizzle in some
areas. Expect cloudy, foggy, and drizzly conditions for the next
couple of hours, with conditions starting to improve mid to late
morning. Stratus should retreat to the coast, leaving us a period of
VFR conditions this afternoon. The forecast will be on repeat
tonight, leading to low cigs and reduced vis returning.


&&

.MARINE...
(Today through Friday)
Issued at 307 AM PDT Sun Jul 13 2025

Light to moderate breezes are expected through Monday, with seas
subtly subsiding today. Seas begin to build Monday, as winds
begin to take on a more northerly component especially in the
northern most outer waters. Hazardous marine conditions of fresh
to strong northerly breezes and very rough seas at times are
expected on Tuesday for far northwestern portions of the northern
outer waters. Winds then decrease heading into Wednesday, with
gentle to moderate breezes through Friday.

&&

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

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...KR
MARINE...KR

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