FXUS66 KMTR 182014
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
114 PM PDT Thu Jun 18 2026
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 112 PM PDT Thu Jun 18 2026
- Hazardous beach conditions with increased risk of sneaker waves
and strong rip currents continue through the extended forecast
- Minor HeatRisk through the end of the week with below normal
temperatures expected this weekend
- Temperatures warm and Moderate HeatRisk concerns return by
midweek across the interior
&&
.SHORT TERM...
Issued at 112 PM PDT Thu Jun 18 2026
(This evening through Friday)
Stratus is receding across with the interior while it persists along
the coast. Patchy clearing is expected along the coastline this
afternoon before overcast conditions return this evening. A deep
upper level trough moving into the West Coast is helping the marine
layer to deepen and will bring a very low, but non-zero, chance of
thunderstorms to far northern Sonoma and Napa Counties along the
highest ridgelines. The marine layer is currently between 2000-2500
ft and is expected to remain around that depth through Friday. Given
the deep marine layer and widespread cloud cover this morning, I
continued to lower daytime temperatures for areas below 2000 feet
today and again tomorrow. For Thursday, high temperatures will be in
the 60s along the coast and 70s across the interior lower
elevations. Areas above the marine layer will be warmer, with
temperatures in the 70s to 80s. High temperatures on Friday will be
slightly cooler with highs in the 60s along the coast and 70s across
the interior. Breezy onshore winds (20-30 mph) are possible across
the higher elevations and favored mountain gaps/passes (Altamont
Pass, San Bruno Gap, Salinas Valley, etc).
A non-zero, but very low, chance of thunderstorms exists for far
northern Sonoma and Napa Counties tonight into tomorrow. The current
forecast shows a <5% chance of thunderstorms which is a decrease
from yesterday. In terms of the environment, there is decent mid to
upper level moisture but little to no instability. The bulk of the
moisture and instability are to our north (EKA's CWA) and to our
east (STO's CWA). There is a brief period where thunderstorm
potential looks marginally more promising this evening across
northern Sonoma/Napa Counties but even this is still a less than 5%
chance. If a thunderstorm is able to develop, it is likely to be
tied to the highest ridgelines along far northern Sonoma and Napa
Counties. While thunderstorms remain unlikely, the more likely
scenario is widespread drizzle along the coast. Precipitation will
be light with totals amounting to less than a tenth of an inch.
While this is not a lot of rain, it may be enough to wet coastal
roads and make them slick. Drizzle is most likely overnight Thursday
night into Friday morning which may impact any early morning
commuters.
&&
.LONG TERM...
Issued at 112 PM PDT Thu Jun 18 2026
(Friday night through next Wednesday)
Below normal temperatures and troughing persist through the weekend
before a pattern change takes place Tuesday/Wednesday of next week.
Interior highs will be in the 70s on Saturday while coastal areas
stay in the 50s to 60s. Temperatures start to rise Sunday into
Monday with interior highs returning to the upper 70s to mid 80s
while cooler weather persists along the coast. Upper level troughing
will have progressed eastward by Tuesday with a strong upper level
ridge replacing it. The center of this ridge will be over the desert
southwest but it will bring a return of warmer temperatures to the
Bay Area and Central Coast. The current forecast keeps the hottest
weather across the interior Central Coast, Southern California, and
the Central Valley where 90s to low 100s are possible. Temperatures
across the Bay Area are forecast to reach the 80s to low 90s
starting Tuesday. Confidence is low to moderate in the late week
temperature forecast given the strength of the ridge and the
relatively large model ensemble spread of forecast temperatures. Not
currently anticipating record breaking heat from this ridge but
would not be surprised if the forecast temperatures did go up
slightly next week as this event gets closer in time. Probabilistic
HeatRisk shows around a 15-20% chance of seeing Moderate HeatRisk
mid next week across the interior Bay Area. This is definitely worth
keeping an eye on and is a reminder that, despite our currently
below normal temperatures, it is summer and temperatures are warming
up. If you are participating in any outdoor activities, make sure to
drink plenty of water and to take breaks in the shade as needed.
&&
.AVIATION...
(18Z TAFS)
Issued at 1043 AM PDT Thu Jun 18 2026
Marine layer continues to gradually erode toward the coast with
VFR conditions already being reported at OAK, SFO, SJC and LVK.
Trends in satellite imagery and latest guidance suggest most other
terminals should see cigs breaking by around 20z, with the
exception of HAF where MVFR cigs could remain in place through the
period. Expect southwesterly winds to become gusty this afternoon,
with greatest potential for gusts of 25kts or higher at SFO and
APC. Winds will weaken after sunset with marine layer stratus
moving in again thereafter as well. Marine layer depth and inland
spread should be similar to what was observed this morning.
Vicinity of SFO...Marine stratus has eroded with a return to
prevailing VFR conditions. Stronger southwest winds will develop
this afternoon with gusts in the 20-25 kt range. Expect these
conditions to persist through sunset. Winds will then ease and the
marine layer will begin to move back inland, with MVFR cigs
around 1700ft likely reaching the terminal by around 08z.
Conditions will improve again after sunrise, with cigs forecast to
erode by mid morning.
SFO Bridge Approach...Lingering clouds over the bay may
continue to reduce visibility for the next few hours. Otherwise
conditions should be similar to SFO.
Vicinity of SJC and OAK...VFR conditions should prevail through
the afternoon and evening at both SJC and OAK with west to
southwest winds of around 15 knots and occasional gusts to 20
knots developing this afternoon. Winds should weaken after sunset.
Low stratus deck around 1500ft is forecast to move back into OAK
around the same time as the wind dies down and will persist
through around 15z. Confidence in MVFR conditions at SJC is
lower and have included only a TEMPO group for cigs around 2000ft
in the 11-15z time frame.
Monterey Bay Terminals...Marine stratus continuing to result in
MVFR conditions at both MRY and SNS. Conditions currently forecast
to improve to VFR in the 20-22z time frame at MRY based on latest
trends in satellite and model forecast data. However, there is
less confidence that SNS will see similar clearing, and thus have
included a TEMPO even after 20z to account for the possibility of
lingering MVFR cigs. Even if marine stratus does clear at SNS,
expect it to move in again by around 00z. Stratus should fill back
in at MRY closer to 04z. In both terminals, once the stratus
moves back in, expect MVFR conditions to persist through the
remainder of the TAF period.
&&
.MARINE...
(Today through Tuesday)
Issued at 927 AM PDT Thu Jun 18 2026
Winds will increase this afternoon and early evening and once
again on Friday afternoon and early evening leading to hazardous
conditions for small crafts in the San Pablo Bay, San Francisco
Bay, Suisun Bay and Monterey Bay. Expect moderate chop along with
the increasing afternoon winds each day. Southwesterly swell with
light to moderate seas will continue into the weekend, with
moderate west to southwest winds across the outer waters.
&&
.BEACHES...
Issued at 156 PM PDT Wed Jun 17 2026
Long period southerly swell at around 15 to 17 seconds will persist
through early Saturday as energetic storms in the Southern
Hemisphere continue to affect the California coast, especially for
south and southwest facing beaches. Hazardous beach conditions
are advertised, specifically for moderate to steeply sloped
beaches along the Pacific Coast of the North Bay, San Mateo, Santa
Cruz counties. A Beach Hazards Statement for Pacific Coast
beaches continues through late Friday night. Be sure to check
beach conditions before you head out. Sneaker waves will run up
the beach much farther than other waves, potentially catching
beachgoers by surprise and resulting in people being swept into
the water. Rip currents are strong enough to pull the strongest
swimmers away from shore. Swim near a lifeguard if possible. Stay
back from the beach, and away from jetties, piers, beachside
rocks, and other infrastructure near the water. Never turn your
back to the ocean!
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through late Saturday night 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 3 PM to 9 PM PDT Friday for Mry Bay-SF
Bay N of Bay Bridge.
&&
$$
SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...Manning
MARINE...Manning
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Prepared by Boulder-Creek.com Weather at: Thu Jun 18 16:30:03 PDT 2026
From the National Weather Service
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