FXUS66 KMTR 172330
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
430 PM PDT Sun May 17 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 120 PM PDT Sun May 17 2026
- Breezy to windy conditions, especially across the North, East,
and South Bay Mountains and the Santa Cruz Mountains through
Monday
- Hazardous beach conditions through Monday
- Hazardous marine conditions expected through Monday
- Elevated fire weather concerns continue through Monday across
the interior with low humidities and strong gusts
&&
.SHORT TERM...
Issued at 120 PM PDT Sun May 17 2026
(This evening through Monday)
Winds eased overnight but are starting to ramp again across the
region but especially across the higher elevations. While winds were
predominantly onshore over the last few days, this next round of
wind will be offshore. Synoptically, a ridge of high pressure sits
to our west over the Pacific Ocean while a positively tilted upper
level trough moves into the Intermountain West. The orientation of
these two features will promote North to Northeast winds across our
region or offshore flow. The SFO-WMC gradient has largely been
weakly positive (onshore) the last few days but is expected to
become negative (offshore) and strengthen today into early tomorrow.
Current guidance has the SFO-WMC gradient peaking around -7 to -8 mb
which supports gustier offshore winds. The SFO-ACV remains strong
around -8 to -8.5 mb indicating good northerly flow will continue.
These winds will be strongest across the higher elevations of the
North Bay, East Bay, South Bay, and Santa Cruz Mountains where gusts
to around 50 mph and locally higher gusts up to 60 mph are expected
this evening into tomorrow morning. The strongest winds are expected
to occur overnight tonight through late tomorrow morning. A Wind
Advisory is in effect from 11PM tonight through 11AM Monday for
these locations. While not as strong as across the higher
elevations, winds will still be breezier across the rest of the
region. Guidance currently keeps winds gusting between 25 to 35 mph
(below Wind Advisory criteria) but we may see a few stronger gusts
mix down into the lower elevations at the base of mountainous
terrain. Winds are then expected to diminish through the remainder
of the day on Monday. High temperatures remain seasonably cool today
in the 70s to low 80s across the interior and 50s to 60s along the
coast. Slightly warmer temperatures are expected tomorrow with
coastal temperatures in the 60s to low 70s and interior highs in the
70s to 80s.
Extremely dry conditions continue through midweek with elevated fire
weather concerns across the interior Bay Area and Central Coast.
Daytime humidity values will be incredibly dry with the higher
elevations dropping to between 10-15% today. A few fires have been
reported across the interior this morning including the Pass Fire in
Alameda County (Altamont Pass region). Fuels are expected to rapidly
dry as strong offshore flow develops today into tomorrow which is
likely to lead to an increase in grass fires. Take care while
participating in any outdoor activities involving fire. Remember,
one less spark, one less wildfire.
&&
.LONG TERM...
Issued at 120 PM PDT Sun May 17 2026
(Monday night through next Saturday)
Broad upper level troughing will push eastward by midweek with high
pressure generally restrengthening over the West Coast. The center
of the ridge and surface high pressure looks to be farther north
closer to the PNW while a weak upper level trough lingers over SoCal
and Arizona. This setup would support a return on onshore
(northwest) winds but they will not be as gusty as those experienced
this weekend. The surface pressure gradient will be more widespread
(i.e. not as tight) as it was this weekend and it will lose upper
level support with the polar jet stream shifting northwards and the
tropical jet stream shifting south. While the winds are dying down,
temperatures are starting to warm up. The return of ridging and high
pressure will allow a warming trend to kick off this week and see a
return of 80s/90s to the interior and 60s/70s along the coast.
Patchy moderate heatrisk is expected across interior, urban areas
this week with temperatures running around 10-15 degrees above
normal. The question is how much of a marine influence will we see
this week and will it be enough to keep our coastal areas/portions
of the interior cooler this week. Right now, high resolution
guidance keeps a shallow (500 ft) marine layer present through mid
to late week which would keep its influence (fog, cooler temps) tied
to more coastal areas.
&&
.AVIATION...
(00Z TAFS)
Issued at 428 PM PDT Sun May 17 2026
Currently VFR at all terminals with the exception of haze being
observed at HAF. High confidence in VFR through the TAF period;
however, haze will reduce slant range visibilities. Strong and gusty
onshore winds will veer tonight to become northerly/offshore with
onshore flow returning tomorrow afternoon. Low level wind shear
(LLWS) has been included in the TAFs starting between 03Z and 05Z
this evening and continuing through 18Z tomorrow morning. The end
time is pessimistic with most LLWS activity expected to occur once
the atmosphere decouples tonight until it recouples tomorrow
morning, probably closer to 15Z. LLWS is primarily expected between
FL015 and FL020 with speeds of 35-45 knots out of the
north/northeast.
Vicinity of SFO...Currently VFR with gusty westerly flow. High
confidence in VFR through the TAF period. Winds will veer tonight to
become northerly before returning onshore tomorrow afternoon.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Currently VFR with westerly flow at both
terminals. High confidence in VFR through the TAF period. Diurnal
winds are expected through the TAF period.
&&
.MARINE...
(Tonight through next Friday)
Issued at 428 PM PDT Sun May 17 2026
Strong surface high pressure will remain nearly stationary over
the eastern Pacific this week. This will result in widespread
strong and gusty northwest winds across the coastal waters. Rough
seas continue through late today with up to 19 ft waves during the
strongest winds, but seas will 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 Pinos to Pt Piedras Blancas 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.
Gale Warning until 9 AM PDT Monday for Pt Arena to Pt Reyes 10-
60 NM.
&&
$$
SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...Sarment
MARINE...Canepa
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Prepared by Boulder-Creek.com Weather at: Sun May 17 20:30:02 PDT 2026
From the National Weather Service
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