Technical NOAA Weather Discussion

FXUS66 KMTR 230425
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
925 PM PDT Sun May 22 2022

.SYNOPSIS...Temperatures begin to warm and humidity levels decrease 
for inland areas through the middle part of the week, with warmest 
temperatures likely on Tuesday. Though coastal areas will warm as 
well into mid week, persistent onshore flow will likely keep these 
areas cooler. Widespread cooling returns as the marine layer 
tries to rebuild late in the week.

&&

.DISCUSSION...as of 09:25 PM PDT Sunday...High pressure building 
over the eastern Pacific is well in control of the weather pattern
over the Bay Area and Central Coast this evening. Sky conditions 
are mostly clear except for a few passing high clouds streaming 
southward from the north. A few patches of stratus did develop 
earlier this evening along the Monterey Peninsula, yet have since 
dissipated thanks to the drier air mass aloft. Thus, cannot rule 
out enough moisture in the boundary layer to produce a few patches
of low clouds, yet widespread stratus is unlikely tonight into 
Monday morning. As the ridge aloft strengthens and builds 
eastward, the warming trend will continue through the first half 
of the week. This said, the ongoing forecast in the short- term 
remains on track with no updates anticipated this evening. For 
more on the heat and near-critical fire weather conditions over 
the North Bay Interior Mountains and East Bay Hills, please see 
the previous forecast discussion below.

&&

.PREV DISCUSSION...as of 01:50 PM PDT Sunday...Sunny skies 
prevail for a majority of the forecast are this afternoon. The 
morning clouds have dissipated in the Salinas Valley, but continue
to hug the coastline around Monterey Bay. Sunny skies and temps 
in the upper 60s to lower 80s, what else could you ask for?

The large area of high pressure over the EPAC will be the main
driver of sensible weather for the Bay Area and Central Coast
through midweek. The ridge flattens as a trough of low pressure
moves through later in the week bringing cooler temperatures
lasting through Memorial Day Weekend.

Tonight through Wednesday: The main weather impacts through
midweek include:

Temperatures: The gradual warming trend noticed over the weekend 
will continue and bring a sneak preview of summer Tuesday and 
Wednesday for interior areas. No significant changes to the 
previous forecast as confidence remains high for hot weather 
impacting interior portions of the Bay Area/Central Coast. The
latest ECMWF EFI has expanded its coverage for above normal
temperatures. Additionally, calibrated ensembles have finally
caught up on heat potential and have been trending warmer. If
anything, the forecast was nudged slightly warmer, both day and
night through Wednesday. The peak of the heat still appears to be
on Tuesday were a few records could fall across the interior.
Therefore, Heat Risk values have also increased for Tuesday, but
still not high enough to warrant a heat advisory at this point.
Highs Monday: mid 60s/near 80 coast and 80s/low 90s inland.
Tuesday: 70s/mid 80s coast and upper 80s/near 100 inland.
Wednesday: upper 60s/low 80s coast and upper 80s/upper 90s inland.
Overnight lows will generally be in the upper 40s/50s valleys and
upper 50s/low 70s in the hills.

Wind: Upper level flow will gradually turn northerly to offshore
Sunday night into Monday. At the surface, onshore flow will
linger Monday, which is why coastal areas are cooler than inland
area. Offshore flow will become more pronounced and stronger 
Monday night into Tuesday, especially for the N and E Bay with 
gusts of 40+ mph. Winds will ease a little during the day Tuesday,
but remain offshore. Another burst of offshore flow Tuesday night
into Wednesday, especially for the hills. These two rounds of
offshore flow will be gusty, but not strong enough to warrant an 
advisory.

Fire Weather: Fire weather concerns will definitely be elevated
through mid week due to hot weather, offshore flow, and lowering
humidity. The offshore flow kicking in later tonight will set the
stage to bring in lower humidity readings. Latest hi-res guidance
begins the real downward trend in humidity Monday night into
Tuesday. Little in the way of overnight humidity recoveries in 
the hills. By Tuesday, critically low humidity readings are being 
advertised across the interior with single digit to low teen 
humidity and no recovery Tuesday night into Wednesday. 
Meteorologically speaking conditions are there, but after 
consulting with some of our fire partners large fuels are 
borderline. That being said, will not be issuing a Fire Weather 
Watch for Tuesday at this time. Will fire starts be possible? Yes,
but not likely to be large in nature. If winds keep trending 
stronger a watch may need to be revisited. Nonetheless, one less 
spark one less fire will be the rule for Tuesday.

Thursday and beyond: The ridge flattens and a trough sweeps
through the area. The passing trough will bring more seasonable
weather back the region heading into the upcoming weekend. 

&&

.AVIATION...as of 5:08 PM PDT Sunday...For the 00Z TAFs. VFR 
across area terminals as mostly clear skies prevail, aside from 
some low clouds around the Monterey Peninsula. Dry northerly flow 
will keep most terminals VFR through the TAF period, except for 
some localized marine stratus developing along the coast tonight. 
Surface winds remain breezy onshore through the evening, with 
gusty winds along the coast and near coastal gaps. Elevated 
northerly winds develop over the ridgetops tonight leading to 
localized but marginal LLWS concerns (North Winds 25-30kt at 
500-2000 feet per site expected overnight with light surface 
winds). Gusty onshore gap winds again tomorrow.

Vicinity of KSFO...VFR. Onshore winds peaking this evening,
sustained near 25 kt and gusts up to 35 kt. Winds remain breezy
well into the night. FEW low clouds reported and observed around
the terminal, but not much cloud development expected tonight or
tomorrow based on model projections and dry airmass in place. 

KSFO Bridge Approach...Similar to KSFO. Marginal LLWS of 25-30kt
at 2000 feet also possible closer to the lee of the East Bay/ 
Oakland hills overnight.

Monterey Bay...VFR at area terminals, but low clouds continue to 
develop over the peninsula in the vicinity of KMRY. Will monitor 
for possible CIG development later this evening. Recent model runs
have backed off on CIG development overnight but given satellite 
observed clouds, CIGs have been retained at KMRY with FEW/SCT at 
KSNS. Any clouds will likely dissipate by mid morning Monday.
Breezy onshore winds diminish tonight.

&&

.MARINE...as of 09:25 PM PDT Sunday...Strong northwest winds 
continue across the coastal waters through the first half of the 
week. The strongest winds will be found near coastal jets and in 
the northern outer waters, where low end gale force gusts are 
possible. As a result, hazardous seas with steep wave heights will
persist through early to mid week as the seas remain wind- 
driven. Expect wave heights of 9 to 12 feet at 8 to 10 seconds in 
the outer waters, which will slowly diminish throughout the week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM
             GLW...Pt Arena to Pigeon Pt 10-60 nm until 3 AM
             GLW...Pt Arena to Pt Reyes 0-10 nm

&&

$$

PUBLIC FORECAST: RGass/MM
AVIATION: Lorber
MARINE: Lorber

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Prepared by Boulder-Creek.com Weather at: Sun May 22 22:30:03 PDT 2022
From the National Weather Service