FXUS66 KMTR 220421
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
921 PM PDT Sun Jun 21 2026
...New AVIATION...
.KEY MESSAGES...
Updated at 1123 AM PDT Sun Jun 21 2026
- Hazardous beach conditions along the Pacific Coast through
Wednesday
- Minor HeatRisk with below normal temperatures through Monday
- Areas of moderate HeatRisk across the Santa Clara Valley and
East Bay Interior Valleys Tuesday through Thursday, peaking
Wednesday
&&
.SHORT TERM...
Issued at 1123 AM PDT Sun Jun 21 2026
(This afternoon through Monday night)
The first day of astronomical summer will be a textbook one for the
Bay Area and Central Coast. A deep marine layer that penetrated
inland last night will slowly retreat towards the coast through the
morning. Stratus will linger at the coast through the day, keeping
temperatures below normal. Elsewhere, expect near normal
temperatures with minor HeatRisk. Heights will begin to rise today
as upper-level shortwave ridging drifts in from the Eastern Pacific
Ocean. This will kickoff a warming and drying trend, compressing the
marine layer in the process. As such, expect warmer conditions with
minor HeatRisk and less stratus extent tomorrow.
&&
.LONG TERM...
Issued at 1123 AM PDT Sun Jun 21 2026
(Tuesday through next Saturday)
High pressure across the Desert Southwest/Northern Mexico will
strengthen and build northwestward Tuesday, continuing the warming
and drying trend. Areas of moderate HeatRisk are expected Tuesday
through Thursday across the Santa Clara Valley and East Bay Interior
Valleys, with the greatest extent coinciding with the warmest day of
the week on Wednesday. The marine layer will start out around 1,500
feet on Tuesday and compress to near 1,000 feet by Thursday. As
such, less and less stratus extent is expected each subsequent
night. This will keep temperatures at the coast below normal and
temperatures inland slightly above normal. No records are in
jeopardy.
Global ensemble clusters are in agreement that upper-level troughing
will be along the West Coast by Friday, deepening the marine layer
as a result. Temperatures will cool to near normal for the interior
and remain below normal at the coast. By Saturday, widespread below
normal temperatures are expected. A passing cold front will increase
onshore winds Friday and into the weekend. Across the land, wind
gusts of 30-40 mph are expected across ridgelines and through gaps
and passes. Over the waters, widespread hazardous conditions for
small craft are expected. There is also a surge in PWAT to near one
inch so drizzle will be possible, especially along the coast.
&&
.AVIATION...
(06Z TAFS)
Issued at 921 PM PDT Sun Jun 21 2026
It's VFR except for stratus /MVFR-IFR/ along the coastline and
locally inland. Onshore winds will continue to usher stratus
/MVFR-IFR/ inland tonight and Monday morning. Stratus mixes out
to the coastline with conditions improving to MVFR-VFR by late
Monday morning and afternoon. Coastal stratus redevelops Monday
night and Tuesday morning.
Vicinity of SFO...Stratus /MVFR-IFR/ is forecast to return to the
terminal this evening. Stratus /MVFR-IFR/ prevails tonight and
Monday morning with mix out to VFR 19z Monday. Stratus /MVFR/
returns mid Monday evening. West wind near 10 knots tonight,
increasing to 12 to 20 knots beginning 19z Monday afternoon, then
easing to near 10 knots mid Monday evening.
SFO Bridge Approach...Similar to SFO.
Vicinity of SJC and OAK...For SJC Airport VFR for the evening,
then stratus /MVFR-IFR/ overnight then mixes out to VFR 19z
Monday. Northwest wind 10 knots tonight to Monday. For OAK Airport
stratus /MVFR-IFR/ prevails tonight and Monday morning, mixing
out to VFR 19z. West wind 5 to 15 knots.
Monterey Bay Terminals...Stratus /IFR/ prevails tonight and
Monday morning. Conditions improving to MVFR-VFR late Monday
morning and afternoon. Stratus /IFR/ returns Monday evening and
night. Onshore winds 5 to 15 knots.
&&
.MARINE...
(Tonight through next Saturday)
Issued at 839 PM PDT Sun Jun 21 2026
Tonight through early Monday morning north to northwest fresh to
strong winds continue over the northern outer waters, resulting
in hazardous conditions for small craft. For other inner and outer
water, north to northwest winds will be light to moderate. Long
period southwest swell will persist through the extended forecast.
&&
.BEACHES...
Issued at 308 AM PDT Sat Jun 20 2026
Long period southerly swell at around 15 to 17 seconds will
persist for the remainder of the weekend, and increase to 17 to
19 seconds by the middle of the upcoming work week 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 Wednesday
afternoon. 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 Wednesday afternoon for CAZ006-
505-509-529-530.
PZ...Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt
Reyes 10-60 NM.
&&
$$
SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Canepa
MARINE...Malarkey
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Prepared by Boulder-Creek.com Weather at: Sun Jun 21 22:30:02 PDT 2026
From the National Weather Service
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