FXUS66 KMTR 180809
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
109 AM PDT Thu Jun 18 2026

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 1245 AM PDT Thu Jun 18 2026

 - Hazardous beach conditions with increased risk of sneaker 
   waves and strong rip currents.

 - Minor HeatRisk through the end of the week with temperatures
   decreasing to below normal.

 - Warming temperatures early next week with Moderate HeatRisk
   concerns by midweek in interior locations.

&&

.SHORT TERM...
Issued at 1245 AM PDT Thu Jun 18 2026 
(Today and tonight)

Satellite imagery early this morning indicates low clouds 
expanding within a 1500-2000 ft deep marine layer, which is 
slightly deeper than the past couple of days. The stratus will 
follow a typical pattern today, continuing to expand in coverage 
early this morning and then decreasing after sunrise before 
retreating back to near the coast during the afternoon. Patchy 
drizzle will also develop along the coast this morning. The flow 
will remain onshore today and increase slightly from yesterday. 
Winds will be breezy this afternoon and evening, especially near 
SF Bay and Monterey Bay as well as adjacent valleys where gusts 
should locally reach 20-30 mph. The marine layer and onshore winds
will keep temperatures similar or a degree or two cooler near the
coast today, with highs ranging from the upper 50s to around 70
degrees, generally slightly below normal. An approaching trough 
will further reduce temperatures inland, decreasing around 5 
degrees on average from Wednesday. This will place highs in the 
70s and 80s, or around 5-10 degrees below normal in most areas, 
resulting in Minor HeatRisk. Tonight, expect stratus to fill back 
in within the marine layer with patchy drizzle redeveloping along 
the coast.

Additionally, north and east of our area, there will be enough 
moisture and instability ahead of the trough for showers and
thunderstorms to develop. Weak elevated instability above the 
stable marine layer will extend just far enough south into 
northern Sonoma and Napa counties for a 5% chance of showers and 
thunderstorms in these areas. Chances for showers/storms will be 
even lower further to the south. The main takeaway is that while 
the potential for shower/storm development is very low, we cannot 
completely rule out an isolated shower or thunderstorm across 
northern areas.

The long-period southerly swell will continue to bring a risk for
sneaker waves and strong rip currents, with a Beach Hazards 
Statement out through late Friday night. See the BEACHES section 
for more information, but the main takeaway is to never turn your 
back to the ocean!

&&

.LONG TERM...
Issued at 1245 AM PDT Thu Jun 18 2026 
(Friday through Wednesday)

The trough off the coast will begin to move onshore on Friday,
then linger over the area into the weekend. Weak elevated 
instability across the north will keep a 5% chance of showers and 
thunderstorms across northern Napa and Sonoma counties on Friday.
Otherwise, temperatures will continue to trend lower, especially 
inland, on Friday as the marine layer deepens further and cooler 
air arrives with the trough. Highs near the coast should remain in
the upper 50s to around 70 degrees, and inland should decrease 
another 5 degrees or so. Temperatures in most areas will remain 
similar on Saturday, but begin to increase inland by Sunday as 
the trough weakens. Expect stratus each night/morning with patchy 
coastal drizzle.

Ensembles remain in agreement that a ridge will build across the 
West early next week. This will bring a warming trend, especially 
inland, with some interior locations reaching the 90s once again 
and Moderate HeatRisk concerns by midweek.

&&

.AVIATION...
(06Z TAFS)
Issued at 958 PM PDT Wed Jun 17 2026

MVFR-IFR stratus is expanding into the valleys and will impact most 
terminals through the night as the breezy and gusty southwest 
pattern winds continue to diminish, with low to moderate confidence 
in stratus impacts at LVK and SJC, where the marine layer is thick 
enough to bring stratus into both terminals but the lower level 
southwest flow may inhibit stratus flow into those areas. The night 
shift will monitor conditions through the night. Stratus should 
retreat to the coastal areas through Thursday morning and the breezy 
and gusty southwest pattern winds should resume in the afternoon.

Vicinity of SFO... VFR with breezy and gusty southwest winds at the 
terminal through the next few hours. Due to the downslope flow, have 
pushed back the MVFR-IFR stratus impacts to around 10Z. Stratus will 
dissipate through Thursday morning with breezy southwest winds 
returning to the terminal in the afternoon. Stratus will return to 
the terminal area late Thursday night.

SFO Bridge Approach... Lower confidence of stratus impacts tonight 
with the large scale southwest flow, as high resolution models tend 
to keep the stratus deck away from the approach path. Otherwise 
similar to SFO.

Vicinity of OAK and SJC... IFR stratus through the night at OAK, 
with breezy west winds diminishing through the next couple of hours. 
At SJC, the stratus forecast remains low confidence. High resolution 
model output keeps the terminal area clear, but places scattered 
MVFR stratus in the vicinity and particularly to the north of the 
terminal. If stratus does impact the terminal, the most likely 
timing is from 11-15Z. Stratus clears out through Thursday morning 
as breezy and gusty winds return to the terminals, with west winds 
developing at OAK, and southwest winds developing at SJC. Stratus 
returns to OAK late Thursday night.

Monterey Bay Terminals... MVFR stratus has flowed over SNS and will 
remain through the night. At MRY, large scale southwest flow has 
sheltered the terminal from the larger stratus deck, defying much of 
the high resolution model output, but a patch of stratus developing 
to the immediate southeast of the terminal suggests that the 
ceilings are close by. Stratus will retreat to the immediate coast 
Thursday morning and will return to the terminals Thursday evening. 
Breezy winds will diminish through the night before resuming on 
Thursday afternoon with strong gusts and a turn from a southwest 
wind at MRY and a northwest wind at SNS.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 958 PM PDT Wed Jun 17 2026

West to southwest winds driven by a weak low pressure system in
the northern outer waters will remain gentle to moderate
overnight. Winds increase again for the next couple afternoons and
evenings with strong breezes anticipated, leading to hazardous
conditions for small craft. Light to moderate seas with
southwesterly swell will continue into the weekend. Moderate  west
to southwest winds and moderate seas will prevail over the  open
ocean into the weekend.

&&

.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 Friday night for CAZ006-505-
     509-529-530.

     Coastal Flood Advisory until 5 AM PDT Thursday for CAZ006-506-
     508.

PZ...Small Craft Advisory from 3 PM to 9 PM PDT Thursday for Mry Bay-
     SF Bay N of Bay Bridge.

&&

$$

SHORT TERM...Tangen
LONG TERM....Tangen
AVIATION...DialH 
MARINE...DialH

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Prepared by Boulder-Creek.com Weather at: Thu Jun 18 04:30:03 PDT 2026