FXUS66 KMTR 182150

Area Forecast Discussion
National Weather Service San Francisco Bay Area
250 PM PDT Wed May 18 2022

.SYNOPSIS...Warm temperatures the rest of this afternoon will
remain mild tonight. A modest cooling trend Thursday as a dry
cold front moves into Nevada creating breezy north winds across
the region. North winds increase Thursday night into Friday
leading to increased fire weather concerns with lowering humidity
and gusty ridgetop winds. Seasonably warm and dry weather
continues this weekend and into next week. Forecast remains dry
the next 7 to 10 days.


.DISCUSSION...as of 2:50 PM PDT Wednesday...Temperatures have
warmed into the 90s for inland areas (93 Santa Rosa with 96 Arroyo
Seco noted so far) this afternoon as high pressure has nosed over
the region with a strong northerly gradient down the coast
creating gale force winds over the ocean waters.

Forecast focus is on inside slider that will drop into the Great
Basin on Thursday setting up some locally strong winds Thursday
evening into early Friday.

Some increasing northeast winds tonight will mainly stay elevated
at the ridgetop level but keep temperatures mild in the hills
overnight. The shortwave will drop into Nevada on Thursday with
just enough cool advection to allow for a few degrees of cooling
on Thursday afternoon as we lose the northerly gradient briefly.
Thus 90s should be less widespread tomorrow with more upper 80s
for inland afternoon highs.

A burst of northeast offshore winds will then work down the
Central Valley late Thursday afternoon and into Thursday evening.
There will be a brief 3-6 hour window of gusty winds and low
humidity, mainly focused over the Napa Hills, eastern Contra Costa
county and the East Bay hills. During this time, gusts in the
40-50 mph range certainly possible with of course higher gusts for
Mt Saint Helena, Diablo, Altamont. When all is said and done the
main impact looks to be to rapidly dry the fuels as we move into
peak fire season. That being said the conditions will favor rapid
spread of any new fires but live fuels still somewhat moist and
the dead fuels still drying out so both fuels and weather
conditions are not expected to be extreme.

During a more classic offshore wind event we would expect to see
humidity values actually lowering during the overnight hours. In
this instance, humidity will stay low but values look to stay
above the night time 30 percent threshold (on average) that we
usually look for. Breezy northeast/offshore winds will continue
into Friday with continued lowering of the RH values but the
strongest winds will end by sunrise Friday. So elevated fire
danger and fire weather concerns will definitely be in play
Thursday into Friday but the best alignment of strong winds and
dry fuels will mostly stay over the Central Valley.

Seasonably warm and dry pattern continues into the weekend but
with generally light winds. Not expecting any hot temps near the
coast as onshore flow stays in place. Will note that the
persistent gale winds have induced strong upwelling over the last
several days with SST temps now running in the upper 40s, keeping
the seabreeze strong and cold along the coast.


.AVIATION...as of 11:00 AM PDT Tuesday...For the 18Z TAFs. VFR
through the TAF period for all but the Monterey Bay, which will
see moments of MVFR CIGs into the late tonight. Winds will become
breezy to gusty through the evening, but will become light to
moderate overnight. Winds aloft over the North Bay remain strong,
causing concerns for LLWS in the late night though Thursday
morning. Lower clouds will move inland around the Monterey Bay in
the late night with low clouds intermittently affecting MRY.
Thursday looks to be another breezy day region-wide with gustier
conditions around SFO.

Vicinity of KSFO...VFR through the TAF period. Westerly winds will
become strong and gusty this afternoon and last through the evening.
Late night winds will stay breezy but will reduce into the early
morning. Gusty conditions return around the midday Thursday and look
to last through the evening again.

KSFO Bridge Approach...Similar to SFO.

Monterey Bay...VFR with moderate to breezy winds this afternoon.
Winds will reduce and become lighter overnight as stratus begins to
build in the Monterey Bay. Expect moments of MVFR at MRY in the late
night, VFR returns mid morning Thursday.


.MARINE...as of 02:27 PM PDT Wednesday...Northwesterly gale force
wind gusts are expected across the   waters into the weekend.
Strong and gusty winds will also prevail across San Francisco and
Monterey Bays each afternoon and  evening. Strong winds will
generate steep fresh swells through the weekend.


     .Tngt...GLW...Pt Arena to Pt Reyes 0-10 nm
             GLW...Pt Reyes to Pigeon Pt 0-10 nm
             GLW...Pigeon Pt to Pt Pinos 0-10 nm
             GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm
             GLW...Pt Arena to Pigeon Pt 10-60 nm
             GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...SF Bay
             SCA...Mry Bay



MARINE: Murdock

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NWS MTR Office Area Forecast Discussion