Sunnyvale, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

242
FXUS66 KMTR 171144
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
444 AM PDT Sun May 17 2026

...New AVIATION, MARINE, FIRE WEATHER...

.KEY MESSAGES...
Updated at 140 AM PDT Sat May 16 2026

 - Breezy to windy conditions, especially across the North, East,
   and South Bay Mountains along with the Santa Cruz Mountains
   through Monday

 - Hazardous beach conditions through Monday

 - Hazardous marine conditions expected through the weekend

 - Elevated fire weather concerns continue through Monday across
   the interior with low humidities and strong gusts

&&

.SHORT TERM...
Issued at 140 AM PDT Sun May 17 2026 (Today and tonight)

Water vapor imagery shows a broad trough of low pressure over the
West this morning, with one disturbance currently moving across
Nevada. In response to this system beginning to shift east,
pressure gradients are starting to relax from their earlier peak.
At this time, the SFO-ACV is down to -9.5 mbs, while the SFO- LAS
is down to 12.6 mbs. Even though it is still breezy out there,
gusts are mostly less than 40 mph along the coast. Therefore, have
canceled the Wind Advisory to better reflect the current
conditions.

That being said, the winds will still be a concern over the next
24 to 36 hours though, as another disturbance currently over
Western Washington and Oregon dives into the Great Basin later
today and tonight. This disturbances has a more traditional inside
slider trajectory. As a result, expect another round of dry and
gusty winds to develop. This time though, it will be the offshore
pressure gradients that increase. North to northeast 925 mb and
the 850 mb winds will increase to 40 kts over the North and East
Bay after 06z Mon, before spreading south and west through the
night. Therefore, have issued a new Wind Advisory focusing on the
North, East, and South Bay Mountains as well as the Santa Cruz
Mountains for Sunday night through late Monday morning. At this
point in time, expect the gusts to be in the 45 to 55 mph range,
with local gusts above 60 mph at the favored locations like Mount
Diablo. Very dry conditions will accompany these winds, and should
a fire start in dry grass areas, the fuels will carry that fire.
Therefore, caution is encouraged if you have plans to be working
outdoors. One less spark.

&&

.LONG TERM...
Issued at 140 AM PDT Sun May 17 2026 (Monday through Saturday)

As this the broad trough starts to push east on Monday, high
pressure will start to rebuild over California, and be the dominate
weather feature through midweek. As a result, a gradual warming
trend will develop, especially across the inland areas. Expect
some warming at the coast as well, but it will be more moderated,
especially once the marine layer re-estabilishes itself by
Wednesday. Models start to diverge towards the end of the week and
next weekend, with some clusters suggesting another trough forming
off the West Coast, while others suggest a flatter ridge, while
others suggest the ridge persisting. Therefore, confidences is
relatively low on what will actually happen. However, believe the
marine layer will likely continue to bring low clouds and fog to
the coastal areas. The question is just how far inland that
influence will go.  Palmer

&&

.AVIATION...
(12Z TAFS)
Issued at 443 AM PDT Sun May 17 2026

Strong winds aloft continue to move through the region causing some
spotty LLWS concerns into the late morning. Moderate to breezy winds
linger through the mid morning but build across the region through
the day. The gusty winds over the ocean will lead to an increase in
sea spay, causing poorer visibilities over the marine environment
and at near coastal sites, such as HAF and around the Monterey Bay.
Winds reduce into the night, but remain strong aloft, leading to
widespread LLWS both in speed and directions.

Vicinity of SFO...VFR through the TAF period. Breezy winds increase
and become strong into the afternoon with gusts expected to exceed
30 kts. Winds turn more northerly into the evening, with the stronger
winds aloft turning more northeasterly into the night, leading to
LLWS. Winds reduce slightly deeper into the night and align better
with winds aloft.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Sea spray will offer hazy conditions around
the Monterey Bay, causing reductions in visibility. Winds increase
into the afternoon becoming breezy and gusty across the area. Gust
cut off and winds reduce into the night, but stay strong aloft
causing LLWS conditions.

&&

.MARINE...
(Today through Friday)
Issued at 443 AM PDT Sun May 17 2026

Widespread gale force gusts continue to affect the waters. Strong
northerly winds last through the weekend and last into Monday,
with storm-force warnings in effect for the northern outer waters
and the inner waters south of point pinos. The rest of the waters
look to have near or infrequent storm force gusts during that
time. Storm warnings degrade into gales by the late afternoon on
Sunday. Winds begin to ease into that night and into the early
work week. Expect rough seas through the weekend with up to 19 ft
waves during the strongest winds, but seas will also ease into the
work week.

&&

.FIRE WEATHER...
Issued at 443 AM PDT Sun May 17 2026

Strong and gusty north to northwest winds continue to affect the
region, shifting slightly into Sunday afternoon, and becoming
north to northeast. Expect peak gusts greater than 30 mph for most
areas, with around 45 to 55 mph along through gaps and passes,
and across higher terrain. Daytime humidity retentions loos to
stay around 10- 25% across the interior regions and higher peaks,
with limited overnight humidity recoveries. Strong winds persist
into the early Monday before diminishing. Humidities will be slow
to recover into the work week as a light offshore flow will
continue to affect the district.

&&

.BEACHES...
Issued at 140 AM PDT Sat May 16 2026

A Beach Hazards Statement remains in effect for west facing
beaches along the Pacific Coast through 9 AM Monday due to strong
winds over the marine environment leading to hazardously strong
wind waves and overall rough seas. Dangerous swimming, boating,
and surfing conditions can be expected. Large breaking waves can
overpower swimmers resulting in significant physical injury and
increase the risk of drowning. Gusts will stay strong along the
immediate coast, causing blowing and drifting sand and increased
sea spray. Water rescue attempts may be hampered by reduced
visibilities from the sea spray. Remember, NEVER turn your back on
the ocean.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Monday morning for CAZ006-505-
     509-530.

     Wind Advisory from 11 PM this evening to 11 AM PDT Monday for
     CAZ504-512-514-515.

     Coastal Flood Advisory until 3 AM PDT Tuesday for CAZ506.

PZ...Gale Warning until 3 AM PDT Monday for Pigeon Pt to Pt Pinos 0-
     10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-
     10 nm-Pt Reyes to Pigeon Pt 0-10 nm-SF Bay N of Bay Bridge.

     Gale Warning until 9 PM PDT this evening for Mry Bay.

     Storm Warning until 9 AM PDT this morning for Pt Pinos to Pt
     Piedras Blancas 0-10 nm.

     Gale Warning from 9 AM this morning to 3 AM PDT Monday for Pt
     Pinos to Pt Piedras Blancas 0-10 nm.

     Storm Warning until 3 PM PDT this afternoon for Pt Arena to Pt
     Reyes 10-60 NM.

     Gale Warning from 3 PM this afternoon to 9 AM PDT Monday for Pt
     Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...Palmer
LONG TERM....Palmer
AVIATION...Murdock
MARINE...Murdock

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