FXUS66 KMTR 111158
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
458 AM PDT Sat Jul 11 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1210 AM PDT Sat Jul 11 2026
- Warmer temperatures continue into next week with Moderate
HeatRisk returning early next week
- Coastal Flood Advisory for up to 1.7 feet of inundation above
ground level is possible in low-lying areas near shorelines and
tidal waterways
- Slightly increasing confidence in potential for thunderstorms
and elevated fire weather concerns Sunday into early next week
&&
.SHORT TERM...
Issued at 1210 AM PDT Sat Jul 11 2026
(Today and tonight)
Stratus coverage across the interior will be less widespread tonight
as the marine layer compresses to around 500 ft. Stratus is expected
to redevelop along the coast and SF Bay shoreline but not expected
to extend much beyond more coastal areas. Patchy fog and drizzle
become more likely along the coast during the early morning hours as
the marine layer compresses. If you are driving early Saturday
morning, watch for sudden changes in visibility and be prepared to
slow down if necessary.
Upper level ridging continues to dominate the southwestern United
States through much of the long term forecast. The center of this
ridge will gradually shift eastward away from southern California
towards the desert southwest Saturday into Sunday. Temperatures are
forecast to warm slightly (2-3 degrees) on Saturday as the ridge
strengthens and a compressed marine layer stays tied to the coast.
Interior areas will feel this warm up more substantially than the
coast with seasonally warm temperatures in the upper 80s to 90s
expected. The SF Bay shoreline and coastal areas will stay
seasonally cool. High temperatures along the bay will be in the 70s
to 80s while coastal highs will be in the 60s to 70s. Minor HeatRisk
is expected today with patchy Moderate HeatRisk across the warmest
interior locations and higher terrain. The marine layer is expected
to remain compressed around 500 ft again tonight. However, mid and
high level clouds are expected to stream into the region Saturday
night ahead of the monsoonal moisture surge arriving Sunday.
&&
.LONG TERM...
Issued at 1210 AM PDT Sat Jul 11 2026
(Sunday through Friday)
There are two main topics for the Long Term discussion: the
potential for thunderstorms late this weekend into early next week
and the return of Moderate HeatRisk early to mid week.
On the synoptic scale, the center of the upper level ridge will
gradually shift northeastward towards the northern Intermountain
West late this weekend and remain in place through the remainder of
the extended forecast. A monsoonal moisture surge is forecast to
move into California from the Gulf of California late Saturday night
into Sunday. This surge is bringing above normal moisture for this
time of year with PWAT values between 1-1.3" expected which is
around 150-200% of normal. Forecast soundings show the bulk of this
moisture in the mid to upper levels of the atmosphere and much drier
conditions at the surface. There is enough moisture available to
support high based showers but the questions becomes will there be
enough instability to result in thunderstorm development. Model
guidance has trended upwards over the last few days in terms of
forecast available MUCAPE/surface CAPE. By no means is this a
substantial change, however, as models have gone from showing no
instability to pockets of MUCAPE (less than 500 J/kg) across our
CWA. Long range, deterministic guidance from the ECMWF and GFS have
both started showing some potential for showers across our CWA with
some potential for lightning. More interestingly, we are getting
within range of high resolution models (HRRR, NAM, RRFS) which are
consistently showing the potential for thunderstorms Sunday into
Monday across our region. While instability still remains a limiting
quantity, confidence is increasing slightly that we will see some
sort of high based convection and potentially thunderstorm
development late this weekend into early next week. Any storms that
do develop are likely to be dry given their elevated nature but
ensembles do indicate light rain may be possible with the strongest
showers.
The monsoonal moisture surge will additionally bring widespread mid
to high level clouds late this weekend into early next week. This
will prevent overnight radiational cooling, trapping heat at the
surface, and see overnight low temperatures rise. Monday and Tuesday
mornings, interior low temperatures are forecast to be in the low
60s while the higher elevations only drop into the upper 60s to 70s
overnight. Daytime high temperatures will remain in the mid 80s to
90s across the interior while the warmest interior areas reach the
low 100s. Coastal areas stay cooler in the 70s to low 80s. Monday
and Tuesday will see more widespread Moderate HeatRisk across the
higher elevations and extending into urban areas. Make sure to
listen to your body, take breaks in the shade, and stay hydrated if
spending time outdoors early next week. Morning low temperatures
trend cooler, back into the 50s, as mid and high level clouds
coverage dissipates mid to late week. A slight cooling trend begins
Friday with interior highs dropping back into the 80s as the center
of the ridge shifts further east and troughing becomes more dominant
&&
.AVIATION...
(12Z TAFS)
Issued at 453 AM PDT Sat Jul 11 2026
Marine layer continues to gradually compress under building high
pressure, while also continuing to make progress into inland
valleys, all while high clouds have begun to stream across the Bay
Area and Central Coast. Intrusion to and over the terminals has been
spotty at times. High confidence that all terminals except KMRY
and KHAF will be VFR by late morning.
Vicinity of SFO...IFR stratus has hovered in close vicinity of both KSFO and KOAK but
has remained VFR through the early morning hours and is now expected
to remain so through the remainder of the TAF period.
SFO Bridge Approach...Similar to SFO
Monterey Bay Terminals...IFR to near LIFR ceilings will persist through the early morning
hours with KSNS expected to clear out by midmorning, guidance is
confident in maintaining borderline IFR/LIFR ceilings at KMRY until
early afternoon with VFR through the remainder of the afternoon,
and MVFR ceilings returning in the early evening hours.
&&
.MARINE...
(Today through Thursday)
Issued at 453 AM PDT Sat Jul 11 2026
Seas will continue to gradually diminish this weekend with
moderate northwest breezes. The favorable conditions this weekend
will continue into the beginning of next week, with strong winds
returning by the middle of the week.
&&
.FIRE WEATHER...
Issued at 453 AM PDT Sat Jul 11 2026
Warm and dry conditions persist through much of next week,
especially away from the coastal marine influences which are
forecast to persist through much of next week. This will increase
fire weather concerns as fuels rapidly dry out. Fire weather
concerns further increase later this weekend into early next week
as a surge of monsoonal moisture advects northward around the
western periphery of the high pressure over the Desert Southwest
and Intermountain West. If thunderstorms are able to develop, dry
lightning and gusty, erratic outflow winds would be the main
hazards. The limiting factor is the lack of instability over our
region those days. Thus, we will continue to closely monitor these
conditions through the weekend. Given the combination of the
potential for dry lightning and rapidly drying fuels, it is
important to stay up to date on the forecast as it evolves.
&&
.BEACHES...
Issued at 453 AM PDT Sat Jul 11 2026
A Coastal Flood Advisory is in effect for minor high tide
flooding through Thursday July 16th. The combination of a perigean
spring tide (lunar perigee on 7/13 and new moon on 7/14) enhanced
by 3-6 inches of additional water from thermal expansion and
accumulated sea level rise since the tidal datum was established
(1983-2001) will bring high tides up to 1.7 feet above normal.
This will lead to minor flooding of parking lots, parks and roads
with isolated closures expected. For context, in June we reached
2.0 feet above normal and in January we reached 2.5 feet above
normal.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 4 AM PDT Thursday for CAZ006-506-
508.
Coastal Flood Advisory from 8 PM this evening to 4 AM PDT
Wednesday for CAZ505-509-529-530.
PZ...Small Craft Advisory until 9 PM PDT Sunday for Pt Arena to Pt
Reyes 0-10 nm.
Small Craft Advisory until 3 PM PDT Tuesday for Pt Arena to Pt
Reyes 10-60 NM.
&&
$$
SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...JM
MARINE...JM
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Prepared by Boulder-Creek.com Weather at: Sat Jul 11 08:30:03 PDT 2026
From the National Weather Service
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