FXUS66 KMTR 280343
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
843 PM PDT Mon Jul 27 2026
...New UPDATE...
.KEY MESSAGES...
Updated at 216 PM PDT Mon Jul 27 2026
- Breezy onshore winds expected each afternoon and evening through
early midweek
- Gradual warming starting midweek, with Moderate HeatRisk for
interior locations
- Elevated fire weather threat across the Diablo and Santa Lucia Ranges
this week
- Hazardous beach conditions at the Pacific Coast with an
increased risk for sneaker waves and rip currents through the
end of the week
&&
.UPDATE...
Issued at 821 PM PDT Mon Jul 27 2026
While the Bay Area weather may not be known for notable weather
like tornadoes, thunderstorms, or hurricanes on the regular it
definitely shines in the micro-climate department. Today was no
exception for micro-climates. The juxtaposition between the
coastal temperatures and inland temperatures was pretty
impressive. The inland heat was triggered by a warm airmass aloft
and a ridge of high pressure to the east. However, the natural
AC/cooler coastal temps were due to onshore flow and a trough of
low pressure off the coast. For context, in Monterey county alone
max temps struggled to reach 60 and topped out at 59 degrees along
Big Sur, but a short jump eastward over the Santa Lucia Mts max
temps made a run for 100 and topped out at 98. Almost a 40 degree
spread in a short distance. Elsewhere around the Bay Area and
Central, while not as extreme, we did see temps in the 60s/70s
near the coast/bays and upper 70s to 90s inland.
For tonight, expect another night of some marine layer stratus to
develop. Not widespread, but enough to impact the coast and bays.
Should note that some hi-res guidance does suggest areas of
offshore flow. That will limit stratus coverage as well.
Additionally, the offshore flow could keep a few spots warmer and
drier than forecast like the N Bay Mts and Santa Lucia range.
No update need for now.
MM
&&
.SHORT TERM...
Issued at 216 PM PDT Mon Jul 27 2026
(This evening through Tuesday night)
Pleasant conditions persist this afternoon across the
Bay Area and Central Coast. 24 hour tendencies in temperatures
indicate most areas are running anywhere from 1-4 degrees lower than
this time yesterday. While the stratus footprint has dwindled to
the San Mateo coastline, persistent onshore flow is likely the
culprit for the cooler conditions. As troughing continues on
Tuesday, we'll contend with another period of onshore flow.
There's some uncertainty with regard to the inland extent of
marine stratus, but overall, mostly sunny skies are anticipated
late morning and into the early afternoon on Tuesday.
&&
.LONG TERM...
Issued at 216 PM PDT Mon Jul 27 2026
(Wednesday through next Sunday)
Wednesday will be the start of our warming trend. The
region will be on the backside of the aforementioned upper level
trough with the Pacific Southwest Ridge projected to gradually
expand westward Wednesday and into Thursday. While another compact
upper level wave will move eastward onto the Oregon Coast late
Thursday, it's impact on our weather seems to be an increase in
the winds over the marine environment thanks to the development
of several coastal jet features. This, in theory, could help
induce upwelling which may promote marine stratus development.
However, forecast soundings from traditional NWP along with cross-
sections from the PG&E/SJSU WRF indicate the marine layer
compressing to under 1000 feet (potentially lower through the end
of the week). As such, infiltration of marine stratus should be
limited spatially and at a minimal if at all. If stratus does
develop, it'll likely dissipate rather quickly by mid to late
morning. This promotes moderating temperatures, particularly
across the interior and poor to moderate humidity recovery
(30-50%) at elevation. More intel on this in the fire weather
section below.
Temperature wise, guidance remains in fair agreement with moderating
conditions on Wednesday and into the weekend across the Bay Area
and Central Coast. We still maintain some very diffuse troughing
aloft on the synoptic scale, but the ridge expands more noticeably
Thursday and into the weekend. Confidence has increased that the
ridge will expand sufficiently enough to compress the marine
layer, particularly across the Central Coast where the areal
extent of Moderate HeatRisk increases quickly. There's still a
chance that current MaxT forecasts may need to be trended upward
across interior sections, but likely only on the order of 1-3
degrees. Across the Santa Lucia and Galiban Ranges, pockets of
Major HeatRisk enter the forecast with some on Wednesday, but
especially Thursday and into the weekend. Those recreating across
this region should ensure they are adequately hydrated with plenty
of water and have access to shade. Moderate HeatRisk becomes most
expansive Thursday and into Friday across the remainder of the
Central Coast and this is when the potential for more formal heat
products increases.
While there's strong consensus for hot conditions across the
interior, coastal regions, including the population centers,
model forecasts exhibit a much more significant spread. For
instance, the KSFO MaxT interquartile ranges from the mid-60s on
the low end to low to mid-80s on the high end Thursday and into
the weekend. What will likely modulate just how hot it gets for
coastal locations will be onshore vs. offshore flow. 925mb flow in
the deterministic guidance starts to diminish especially Friday
and into the weekend. As flow drops below 10 knots, there's the
potential for a large degree of variability in direction and
should a given location experience periods of either very weak
onshore flow or offshore winds, MaxT will likely verify on the
higher end of the spread. In the case of KSFO, mid-80s would be
nearly 10-15 degrees warmer than normal. For now the forecast
currently resides on the warmer end of things through at least
Thursday, but additional adjustments will be made as we venture
closer to mid- week. Regardless, it'll be important for those
across the area to remain hydrated with plenty of water, stay cool
and limit strenuous outdoor activities to the cooler portions of
the day. Never leave kids or pets unattended in vehicles! In
addition, if headed to our Pacific coast beaches for relief, be
mindful of the increased risk for sneaker waves and rip currents.
&&
.AVIATION...
(00Z TAFS)
Issued at 456 PM PDT Mon Jul 27 2026
VFR with clear skies except for some spotty stratus directly along
the coast near KHAF. The theme remains mostly the same as we
continue to be at the intersection of a broadening ridge to the
east and persistent troughing over the EPAC. Good confidence that
North Bay terminals will see little to no stratus through the
forecast period. Lower confidence for the coastal areas where the
marine layer is expected to continue to be more unorganized than
usual this time of year.
Vicinity of SFO...Low confidence in whether ceilings will develop after
midnight into the pre-dawn hours. Dry air aloft and potential for
weak offshore flow aloft may result in just spotty, less impactful
stratus development Tuesday morning, with clearing expected by late
Tuesday morning.
SFO Bridge Approach...Similar as SFO.
Monterey Bay Terminals...Higher confidence in stratus eventually developing farther
south into the Monterey Bay terminals with less dry air mixing down
to the surface less potential for offshore flow aloft locally.
Expect some stratus to develop after sunset but remain VFR until
later in the night when it begins to fill in across the bay into the
Salinas Valley. Expect VFR conditions for the remainder of the TAF
period once ceilings lift.
&&
.MARINE...
(Today through Saturday)
Issued at 947 AM PDT Mon Jul 27 2026
Fresh northwesterly breezes increase to strong today, persisting
through the week with frequent gale force gusts along the Big Sur
and Point Reyes coastal jet regions. Moderate seas build to rough
in the outer waters by tomorrow and continue through the week.
Distant tropical cyclones continue to send long period southerly
swells our way through the work week.
&&
.FIRE WEATHER...
Issued at 152 PM PDT Mon Jul 27 2026
The elevated fire weather threat will persist across portions of
the area through mid-week. Overnight RH recovery will remain
moderate at locations at or above 2,000 feet with values around 40
to 50 percent. This will be particularly true across the
Mayacamas, highest peaks of the East Bay Hills, the Diablo Range,
Santa Cruz Mountains, Santa Lucia and Gabilan Ranges. Nocturnal
drying (rapid decrease in RH through the pre-dawn hours) may also
transpire which will increase the burn period or time in which
fire behavior may remain active. Afternoon RH will remain
critically dry with values between 20 and 40 percent, with far
southern portions of the interior Central Coast potentially seeing
min RH near 10 percent. Energy Release Components (ERC) are
projected to climb above the 95th percentile across the interior
Central Coast. Individuals across the area are advised to avoid
activities that may spark a fire. Fire crews are urged to exercise
extra caution when executing any prescribed burns, especially
where fuels, topography, and weather align.
&&
.BEACHES...
Issued at 145 PM PDT Sun Jul 26 2026
Distant tropical cyclones in the Eastern Pacific will continue to
generate 16-18 second (long-period) southwesterly swell which has
reached the coastline of the San Francisco Bay Area and Central
Coast. As such, sneaker waves and strong rip currents are the
primary concerns. Breaking waves can reach up to 12 feet along
some south and southwest facing beaches and break points, such as
Santa Cruz, Pacifica, and parts of Stinson or Ocean Beach. This
can be particularly surprising when wave heights increase suddenly
after a period of seemingly tranquil wave action. In fact,
sneaker waves can have 20+ minutes in between the larger sets
(breaking waves) with significant "flat/calm looking" times
between them. Due to the long period, sneaker waves are powerful
and can catch beachgoers by surprise, resulting in people and pets
being swept into the cold, turbulent ocean. Rip currents are
strong enough to pull even the strongest swimmers away from shore.
Check marine conditions before you head out! Swim near a
lifeguard, if possible. Maintain a safe distance from the water,
and stay away from jetties, piers, beachside rocks, and other
waterside infrastructure. Never turn your back to the ocean and if
you have small children or pets at the beach, please keep an eye
on them. Hazardous beach conditions are anticipated to persist
through Saturday afternoon.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Saturday afternoon for CAZ006-
505-509-529-530.
PZ...Small Craft Advisory until 9 PM PDT this evening for Mry Bay-SF
Bay N of Bay Bridge.
Small Craft Advisory from 2 PM to 9 PM PDT Tuesday for Mry Bay-
SF Bay N of Bay Bridge.
Small Craft Advisory until 3 AM PDT Wednesday for Pt Arena to Pt
Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory until 3 PM PDT Thursday for Pigeon Pt to Pt
Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt
Reyes 10-60 NM.
Gale Warning until 3 PM PDT Wednesday for Pt Pinos to Pt Piedras
Blancas 0-10 nm.
&&
$$
SHORT TERM...Bain
LONG TERM....Bain
AVIATION...JM
MARINE...Navarrete
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Prepared by Boulder-Creek.com Weather at: Mon Jul 27 22:30:03 PDT 2026
From the National Weather Service
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