Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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FXUS66 KMTR 242353
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
453 PM PDT Tue May 24 2022

.SYNOPSIS...Hot and dry conditions continue this afternoon with
near-critical fire conditions in the North Bay Interior Mountains
and the East Bay Hills. Widespread 90s are forecast for the
interior today and again on Wednesday. Cooling trend starts on
Thursday. Chances for rain should stay just north of Sonoma County
on Saturday. Otherwise the forecast for the holiday weekend looks
rather pleasant.

&&

.DISCUSSION...as of 02:10 PM PDT Tuesday...High pressure centered
over the Eastern Pacific Ocean is bringing clear and sunny skies
to California. With ample sunshine heating the surface coupled
with a warming airmass aloft, we are seeing notably warm
temperatures across the CWA. The airmass aloft is forecast to peak
at 20-22 degrees C at the 850 mb level (for reference, average
850 mb temps based on climatology is closer to 16 degrees C for
this time of year). At noon, Santa Rosa had already reached 91
degrees while Livermore hit 90. Between noon and 1 pm, many more
sites bumped up into the low 90s: Concord, Novato, Hollister,
Scott`s Valley, Pinnacles Natl Park, Carmel Valley, Fort Hunter
Liggett.

We are still on track for highs this afternoon to peak in
the mid to upper 90s for many of our interior sites. Closer to
the coast, winds remain onshore and our coastal residents won`t be
dealing with 90s, but rather stay in the upper 60s to 70s. So if
you`re living in the interior and need a reprieve from the heat,
the coast may feel more comfortable to you.

As for winds, we`re still seeing N to NE offshore winds in
the interior North Bay & East Bay hills, but gusts have lessened
since this morning (up to 40 mph) to 20-30 mph this afternoon. We
continue to headline the near-critical fire weather conditions in
our Fire Weather Forecast due to the warm and dry conditions with
offshore winds. The main mitigating factor as to why we are not in
a Red Flag Warning is that the heavier fuels are not completely
cured, yet. The grasses are dry/cured and can easily burn as we`ve
seen small grass fires pop up across our CWA. However, these
smaller grass fires tend to be more easily contained. The thicker
brush and trees are not completely cured, but are starting to show
signs of stress. We`ll be monitoring those heavier fuels after
this heat event since they are approaching minimum moisture
levels.

As we get into tomorrow, conditions will be similar to today
except for 2 factors: 1) The offshore winds across the interior
North Bay and East Bay Hills will not be as strong and will
actually peak in the overnight hours into early Wednesday morning
instead of blowing during the dry part of the day 2) We are
expecting a Southerly Surge (marine stratus surging northward
along the Big Sur coast and towards the Bay Area). If you`re in
the interior areas of our CWA, you`ll notice similar heat as today
if not a degree or two warmer, but it won`t be as windy in the
hills. For coastal areas, that southerly surge is forecast by our
local WRF and HRRR to move up the CA coast overnight tonight and
should be rounding the bend into the Monterey Bay between 12-15z
which is between 5-8 am local time. Some light southwesterly
winds may reach up towards the SF Bay, but unsure if the stratus
will actually extend that far north. In this southerly surge,
it`ll be likely that the stratus could hit the Santa Cruz area
first before filling into the rest of the Monterey Bay. So if you
live near Santa Cruz or along the Big Sur coast, then expect
cloudier skies tomorrow.

Moving into the second half of the week, we will feel a noticeable
cooling trend with increasing humidity. For example, on Thursday
afternoon, most places will have about a 10-15 degree drop in max
temps. Livermore will go from 96 Wednesday to 83 on Thursday.
Santa Rosa will go from 93 to 76. So expect much more seasonable
temperatures for the rest of the week as onshore winds dominate
our weather pattern. This cooling trend is due to an upper level
low weakening that high pressure system on Thursday as it moves
into the Pac NW and NorCal. This large broad trough is expected to
linger in the area into the weekend and early next week. Although
most of the rain associated with this low will stay well north of
our CWA, some of the extended models are hinting that a bit of
light rain could brush far northern Sonoma county on Saturday and
the NBM reflects this in our forecast.

&&

.AVIATION...as of 4:44 PM PDT Tuesday...For the 00Z TAFs. VFR
through the TAF period for all but the Monterey Bay, which will
see a push of Fog and LIFR CIGs early Wednesday. Winds will become
light to moderate in the evening and overnight. Winds aloft over
the North Bay look to remain strong, causing concerns for LLWS in
the late night for APC. Lower clouds will move inland from the
south around the Monterey Bay in the late night. Wednesday offers
VFR region- wide into the afternoon with light to moderate winds.

Vicinity of KSFO...VFR through the TAF period. Westerly winds will
stay moderate through the evening. Late night winds become light and
variable and these weakened winds will last well into the morning
Moderate westerly winds return around the midday Wednesday and look
to last through that evening.


KSFO Bridge Approach...Similar to SFO.

Monterey Bay...VFR with moderate winds into the night. Winds will
reduce and become lighter overnight. Stratus begins to move in from
the South and build in the Monterey Bay after wrapping around the
peninsula. The stratus and fog will mostly stay over the bay
overnight, but looks to filter into the Salinas Vally early
Wednesday morning. This will cause LIFR at SNS. Expect VFR to return
in the mid morning.

&&

.FIRE WEATHER...as of 03:00 AM PDT Tuesday...Elevated fire
weather concerns are expected on Tuesday due to above average
temperatures, offshore winds and critically low relative humidity.
Strong offshore wind gusts are forecast over the North Bay
Interior Mountains and East Bay Hills with gusts of 25 to 35 mph.
Critically low humidity readings are expected across the interior
with single digit to low teens and little to no recovery Tuesday
night into Wednesday. A southerly surge is looking more likely on
Wednesday ushering in much cooler temperatures and higher
humidity. This will first occur near the coastline and then spread
inland by Wednesday night diminishing fire weather concerns.
Remember: one less spark, one less fire!

&&

.MARINE...as of 04:52 PM PDT Tuesday...Expect northwest winds to
continue to be gusty with the strongest in the northern outer
waters and coastal jets to the south of the prominent points.
Steep wind waves around 10 to 12 feet with a  period of 8 to 10
seconds possible through tonight. However, winds will start to
diminish Wednesday morning. This will help to  improve the sea
state, bringing wave heights down to 6 to 8 feet.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Mry Bay until 9 PM
             SCA...Pt Reyes to Pigeon Pt 0-10 nm until 9 PM
             SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 9 PM
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Pt Arena to Pt Reyes 0-10 nm

&&

$$

PUBLIC FORECAST: Bingaman
AVIATION: Murdock
MARINE: Murdock

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