FXUS66 KMTR 211827
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1127 AM PDT Sun Jun 21 2026
...New SHORT TERM, LONG TERM...
.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...
(18Z TAFS)
Issued at 1050 AM PDT Sun Jun 21 2026
Marine stratus beginning to erode toward the coast as evident in
both satellite and surface-based observations. While MVFR to
locally IFR cigs continue at most terminals, there is moderate to
high confidence of clearing within the next couple hours for most
terminals away from the coast, with clearing near the coast a
little later. HAF may not clear at all. Lower cigs return after
02z Monday with less inland extent than this morning.
Vicinity of SFO...Marine stratus deck around 1000-1500 ft should
scatter out over the next 1-2 hours. Winds will strengthen this
afternoon with gusts to around 25 kts setting in around 21z and
persisting until around 00z, before weakening again with a return
to near 10 kts by around 03/04z. Stratus MVFR to locally IFR
expected to return around the same time with moderate confidence
on timing and cig heights.
SFO Bridge Approach...Similar to SFO. Better chance of intermittent
BKN cigs occurring through the afternoon hours.
Vicinity of SJC and OAK...Satellite imagery trends indicate
clouds should break in the next hour or two at SJC, but will
likely last a little longer at OAK where a return to VFR
conditions may not occur until closer to 21z. NW/W winds will
increase after 21z to around 15 kts with a few stronger gusts of
20 to 25 kts, mainly at SJC. Low clouds around 1200ft return to
OAK 04/05z, lowering to around 800ft after 06z with moderate
confidence. MVFR conditions forecast to return to SJC closer to
daybreak, though confidence is lower whether marine stratus will
spread that far inland. Any marine stratus should begin to clear
again by mid to late morning Monday.
Monterey Bay Terminals...MVFR conditions due to marine stratus
deck around 1200-1500ft should begin to improve at SNS in the
next hour or so, but will persist for a few more hours at MRY.
Moderate confidence in any afternoon clearing near the immediate
coast (MRY) based on latest satellite observational trends.
Moderate to high confidence in MVFR cigs once again pushing inland
after 02z Mon, becoming locally IFR after 05z Mon. Onshore winds
5 to 15 knots.
&&
.MARINE...
(Today through Friday)
Issued at 1050 AM PDT Sun Jun 21 2026
Fresh to strong winds out of the north-northwest will continue
over the northern outer waters through early Monday morning,
resulting in hazardous conditions for small craft. Winds will be
light to moderate over the remaining inner and outer waters. 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...Manning
MARINE...Manning
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea
Prepared by Boulder-Creek.com Weather at: Sun Jun 21 12:30:03 PDT 2026
From the National Weather Service
|