419
FXUS66 KMTR 221615
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
915 AM PDT Wed May 22 2024

...New UPDATE, MARINE...

.SYNOPSIS...
Issued at 1237 PM PDT Tue May 21 2024

Summer-like pattern to persist through Thursday. Temperatures are
forecast to dip below seasonal averages by the upcoming weekend
as an upper level trough impacts the region.

&&

.UPDATE...
Issued at 914 AM PDT Wed May 22 2024

Mostly clear skies over our region with the exception of some areas
over Monterey Bay and Salinas Valley. Satellite shows most of the
clouds are pretty socked in, so expect clearer skies after 10-11
AM in those areas. Temperatures 24 hours ago were a few degrees
below current temperatures. Therefore, expect another day of
warmer temperatures with inland areas reaching up to high 70s with
isolated spots in the low 80s. Forecast remains on track, no
changes were made.

&&

.SHORT TERM...
(Today and tonight)
Issued at 212 AM PDT Wed May 22 2024

Stratus is slowly creeping its way up along the coast from Monterey
Bay through Half Moon Bay. An otter eddy has developed over the
Monterey Bay with stratus cycling cyclonically over the bay. Stratus
coverage is expected to fill in and become more widespread over the
Monterey Bay by the early morning hours. Morning lows will be
slightly cooler than yesterday with more widespread low temperatures
in the upper 40s to mid 50s. High temperatures today will be 3 to 5
degrees cooler than observed yesterday with inland highs in the
upper 70s to low 80s and coastal highs in the upper 50s to low 60s.
Increasingly onshore flow along the coast will help to bring in
moister, cooler air and begin a weak cooling trend. Minor heat risk
continues today and tomorrow for most of the interior Bay Area and
interior portions of the Central Coast. For those who are extremely
sensitive to heat, remember to take breaks while outdoors and to
drink plenty of water.

Broad upper level troughing continues through Thursday with weak
upper level offshore flow contributing to drier conditions inland.
Minimum relative humidity values on Wednesday will be slightly
higher than yesterday as stronger onshore flow along the coast will
bring in increased moisture. Inland daytime RH values will rise by
at least 10% with values ranging from 30 to 45 percent expected. The
driest conditions (daytime RH values around 30%) are collocated with
decent upper level offshore flow over the North and East Bay
Mountains. Along the coast, stronger onshore flow will keep daytime
RH values ranging from the mid 60s to low 80s with moister
conditions extending farther northward today.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 212 AM PDT Wed May 22 2024

A weak cooling trend continues through Thursday before a more
significant temperature drop begins Friday as stronger upper level
troughing dips southward and a weak surface low pressure system
moves inland. High temperatures on Friday and Saturday will be 5 to
15 degrees below average. Inland areas will see highs extending from
the low 60s to low 70s while coastal areas see highs in the mid 50s
to low 60s. Ensemble guidance continues to indicate that light, non-
impactful precipitation is possible with this system but values
continue to be less than a tenth of an inch. Precipitation chances
remain low overall but the most likely scenario suggests light
drizzle along the coast and maybe a trace of rain inland. Stratus
coverage is expected to become more widespread beginning over the
weekend as this system moves through and increased onshore flow
develops. This will follow a typical "May Gray" pattern where
gloomier, overcast conditions are expected throughout the morning
before overcast conditions clear out mid to late morning.

While below average temperatures are expected to continue through
the end of the month, a weak warming trend will begin Sunday as
upper level ridging builds over the West Coast. Temperatures will be
slightly below average to seasonal with inland regions warming back
into the 70s and low 80s and coastal regions continuing to linger in
the upper 50s to mid 60s.

&&

.AVIATION...
(12Z TAFS)
Issued at 415 AM PDT Wed May 22 2024

Generally VFR for all but the Monterey Bay terminals, which will
see overnight/morning IFR stratus. The other exception is at KAPC
which has maintained a TEMPO ceiling over the past few hours.
Otherwise look for breezy onshore winds this afternoon with mostly
clear skies. LLWS potential tonight at KAPC due to decoupling
light surface winds and gusty offshore flow aloft potentially
reaching 30-35 kt at 2 kft AGL.

Vicinity of SFO...VFR but with FEW-SCT010 this morning at the
terminal. Breezy onshore winds this afternoon with gusts to around
25 kt. Winds gradually becoming lighter around/after 05Z.

SFO Bridge Approach...Similar to SFO

Monterey Bay Terminals...IFR stratus persists this morning before
mixing out around 17-18Z. Modest onshore winds develop this
afternoon with some periodic gustiness through the Salinas Valley.
Low stratus returns later this evening and persists into Thursday
morning.

&&

.MARINE...
(Today through Monday)
Issued at 914 AM PDT Wed May 22 2024

Building surface high pressure over the Eastern Pacific Ocean will
continue to allow for strong northwesterly winds to prevail
through Thursday, with gale force gusts across the outer coastal
waters. Expect hazardous conditions and steeper wind waves during
the week. Winds diminish heading into the weekend as surface high
pressure over the Eastern Pacific Ocean weakens and retrogrades to
the west.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this
     evening for Mry Bay.

     Small Craft Advisory from 9 AM to 3 PM PDT Thursday for Mry Bay-
     Pigeon Pt to Pt Pinos 0-10 nm.

     Gale Warning until 3 AM PDT Thursday for Pigeon Pt to Pt Pinos
     10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory until 3 PM PDT Thursday for Pt Pinos to Pt
     Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory until 3 AM PDT Thursday for Pigeon Pt to Pt
     Pinos 0-10 nm.

     Gale Warning until 9 AM PDT Thursday for Pt Arena to Pt Reyes 10-
     60 NM.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...SPM
MARINE...Sarment

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