FXUS66 KMTR 311637
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
937 AM PDT Fri Jul 31 2026
...New UPDATE, MARINE...
.KEY MESSAGES...
Updated at 1216 AM PDT Fri Jul 31 2026
- Gradual warming trend through Saturday with Moderate HeatRisk
in the interior through the early part of next week
- Elevated fire weather threat across the interior North and East
Bays, and the Diablo and Santa Lucia ranges through the early
part of next week
- Hazardous beach conditions across the Pacific Coast with an
increased risk for sneaker waves and rip currents through the
weekend
- Strong and gusty winds develop over coastal waters north of Pt
Reyes this weekend
&&
.UPDATE...
Issued at 934 AM PDT Fri Jul 31 2026
Patches of stratus along the San Mateo coast and the Monterey Bay
region continue to mix out, while smoke from the Woodside Fire
continues to flow into the North Bay valleys. Sonoma County is
dealing with the most intense smoke impacts with haze extending
into Napa and Marin counties. Smoke transport is expected to
continue through the day with peak transport expected as the winds
pick up in the afternoon and evening hours. At the site of the
fire, northwest winds gusting to 25-30 mph are expected this
afternoon and evening. Air quality information is available from
the Bay Area Air District.
DialH
&&
.SHORT TERM...
Issued at 1246 AM PDT Fri Jul 31 2026
(Today and tonight)
Near term Woodside Fire Weather: Satellite imagery shows some heat
still showing up for the Woodside Fire. Thankfully the winds have
eased from what was being observed during the evening hours.
Still seeing some occasional gusts of 10-15 mph nearby. There is
a shallow marine influence still showing up with cooler temps and
moderate to excellent humidity recover. However, go up the hill
on the east side of Hwy 1 just a few 100 feet and it's milder and
drier. There is a little bit of northerly flow over those ridge
tops too, which is likely enhancing the thermal belt. Today's
challenge won't be the temps or humidity, but the winds. Similar
to Thursday NW winds will pick up again and be strongest in the
afternoon/evening. Transport flow will be NW again leading to
smoke transport to the southeast and east.
Weather highlights for Friday: The warming trend observed on
Thursday will continue today as high pressure aloft continues to
ooze westward. Per 00z model guidance 850mb temps warm an
additional 1-3C leading to 3-5F degrees at the surface. That's
assuming a fully mixed atmosphere with no marine layer influence.
In other words, across the interior. Thursday's hottest locations
were 100-103 so a max of 105 isn't out of the question today.
Regardless, solid temps in the 90s to low 100s across the interior.
Those temps will translate to widespread HeatRisk of Moderate with
a few pockets of Major. At the coast and near the bays we still
see subtle onshore flow with natural AC. The temp difference
between the coast and inland will lead to gusty onshore winds this
afternoon again.
Given the nearby fire activity added smoke to the forecast with
greatest coverage over the Sonoma and Petaluma Valleys of the
North Bay. Could see some hazy condition develop over Marin and
Napa as well depending on fire activity this afternoon.
Clouds maybe lacking early this morning, but a weak cold front
will approach from the N on Friday night/Saturday morning with a
higher probability for patchy coastal stratus. Given the warm
airmass aloft expect thermal belts to be active again with only
minor relief expected in the hills.
&&
.LONG TERM...
Issued at 141 AM PDT Fri Jul 31 2026
(Saturday through Thursday)
The aforementioned cold front fades out during the day Saturday
with little to no fanfare. Even with the fading frontal boundary Saturday
still appears to be the hottest day for this round of heat. No
big change to previous forecast. Hottest interior locations of the
Central Coast have the highest probability of exceeding 105
degrees, but less than 10% of reaching 110. Still expecting
widespread HeatRisk of Moderate with a few pockets of Major. At
the coast/bays temperatures will remain closer to seasonal
levels. The large upper level ridge gets buffeted by a passing
upper level trough to the north on Sunday. This will pause any
additional warming with moderating temperatures to round out the
weekend. Cooling 850mb and lower 500mb heights will bring subtle
cooling Monday through the middle of next week. Do want to point
out that even thought we technically cool next week this will be
a prolonged period with max temps in the 90s to lower 100s across
the interior.
As discussed last night it still looks dangerously windy over the
northern coastal waters this weekend, especially Sunday into
Monday. The N-S gradient is still projected to reach 8 to 9mb
resulting in storm force gusts. The ECMWF EFI has doubled down on
tonight's run and is showing decent confidence for the windy
scenario. Thankfully the flow remains mostly parallel to the
coast so a wind advisory win't be needed. The passing system to
the north will help to set the stage for bursts of offshore flow
Saturday and Sunday nights. The setup isn't ideal for strong
winds, but still a change to NE wind. The NE flow will enhance
fire weather concerns. More details below.
&&
.AVIATION...
(12Z TAFS)
Issued at 525 AM PDT Fri Jul 31 2026
Satellite imagery and surface observations show a few areas of
coastal stratus and fog /MVFR-IFR-LIFR/ from Point Reyes to the
Monterey Bay otherwise it's clear /VFR/. Wildfire smoke in the
North Bay will lower surface visibility to MVFR. Diurnal surface
warming and mixing will mix out the stratus, fog and help mix out
the wildfire smoke today. Coastal stratus and fog /MVFR-IFR-LIFR/
return tonight and early Saturday morning under nocturnal radiative
cooling. A dry surface cool front moves southward over the coastal
waters Saturday.
Vicinity of SFO...VFR today and tonight then stratus is likely by
10z Saturday, mixing out to VFR by 18z Saturday. West winds up to 15
to 25 knots today, decreasing to 10 knots tonight and Saturday
morning.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Stratus and fog /IFR-LIFR/ mixes out to
VFR by late morning then redevelops tonight and Saturday morning.
Onshore winds 5 to 15 knots.
&&
.MARINE...
(Today through Wednesday)
Issued at 934 AM PDT Fri Jul 31 2026
Fresh northwest breezes strength by Saturday into gale force
across the northern waters and strong in the southern coastal
waters. Wind driven moderate seas build to very rough by Sunday
in response to the stronger winds. Occasional storm force gusts
are likely in the northern waters. Wind and very rough seas
gradually subside by mid next week. Distant tropical activity
continues to send long period swells to our coastal waters.
&&
.FIRE WEATHER...
Issued at 1216 PM PDT Thu Jul 30 2026
The overall fire weather picture remains similar to the previous
discussion, with elevated fire weather threats persisting at the
higher elevations through the weekend and possibly beyond.
Overnight RH recovery remains moderate to poor at locations at or
above 2,000 feet with values between 35 to 45 percent, with some
favored locations struggling to even reach 25 percent. This will
be particularly true across the Mayacamas, highest peaks of the
East Bay Hills, the Diablo Range, the Santa Cruz Mountains, the
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 remains critically dry with values between
15 and 30 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 97th
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 1216 PM PDT Thu Jul 30 2026
Long period southerly to southwesterly swell of 14-17 seconds
continues to impact our coastline through at least Saturday
afternoon, bringing hazardous beach conditions to the Central
Coast and the San Francisco Bay Area. Sneaker waves and strong rip
currents will be the primary threats, with breaking waves up to
10 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.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Saturday afternoon for CAZ006-
505-509-529-530.
PZ...Small Craft Advisory until 9 AM PDT Saturday for Pt Arena to Pt
Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.
Gale Warning from 9 AM to 9 PM PDT Saturday for Pt Arena to Pt
Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory from 3 PM this afternoon to 9 PM PDT
Saturday for Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt
to Pt Pinos 0-10 nm.
Small Craft Advisory from 9 AM to 9 PM PDT Saturday for Pigeon
Pt to Pt Pinos 0-10 nm.
Small Craft Advisory until 3 PM PDT Saturday for Pt Pinos to Pt
Piedras Blancas 0-10 nm.
Gale Warning from 3 PM to 9 PM PDT Saturday for Pt Pinos to Pt
Piedras Blancas 0-10 nm.
Small Craft Advisory until 9 PM PDT Saturday for Pigeon Pt to Pt
Pinos 10-60 NM.
&&
$$
SHORT TERM...MM
LONG TERM....MM
AVIATION...Canepa
MARINE...Navarrete
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Prepared by Boulder-Creek.com Weather at: Fri Jul 31 10:30:02 PDT 2026
From the National Weather Service
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