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

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FXUS66 KMTR 212032
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
132 PM PDT Sat May 21 2022

.SYNOPSIS...Look for a gradual warming trend this weekend with
more robust warming across the interior early next week. A
cooldown is then likely late next week and into the upcoming
holiday weekend.

&&

.DISCUSSION...as of 01:33 PM PDT Saturday...Pleasant weather over
the weekend, but a taste of summer arrives early next week with
increased fire weather concerns.

Today and Sunday: Upper level high pressure lurking offshore
continues to inch closer to the coast. As 500mb heights increase
aloft skies will remain mostly sunny during the day with a shallow
marine layer developing at night. The shallow marine layer will
result in patchy coastal clouds during the morning hours.
Temperatures today are running a few degrees warmer than Friday
and will peak in the 60s/70s coast/bays and 70s/80s interior.
Temperatures will likely be a few degrees warmer on Sunday,
especially across the interior.

Monday through Wednesday: The upper level high pressure moves over
the region resulting in a robust warm up. The warm up will
initially be across the interior on Monday and then more
widespread Tuesday with slight coastal cooling WEdnesday. Model
trends as of late have been trending warming, especially Tuesday.
ECMWF Extreme Forecast Index continues to highlight much of the
region as being above normal for temperatures day and night
Monday through Wednesday. Additionally, hi-res model guidance is
also showing solid northerly to offshore flow develop Monday night
through Tuesday. This downslope flow will only enhance the heat
potential across the interior. Therefore, temperatures were
nudged upward on Tuesday with the North and East Bay 95-100
degrees in the warmest locations. Max temps were also increased
along the coast due to the warmer northerly/offshore flow. Despite
the bump in temps still not yet record territory, but definitely
above seasonal averages. Temperatures do dip slightly on Wednesday
as the ridge of high pressure weakens and onshore flow begins to
redevelop.

Breezy offshore flow will help to usher in much drier air.
Forecast humidity readings Tuesday afternoon from the WRF are in
the upper single digits to lower teens. Hot, dry, and breezy
conditions will most certainly increase fire concerns Tuesday.
Latest ERC and fuels charts are turning corner toward summer and
the spring rains are being erased. Will have to closely monitor
this the next few days and coordinated with fire partners and
neighboring forecast offices.

Thursday into the Holiday weekend: Widespread cooling is expected
by Thursday as an upper level trough moves through the region.
Interestingly the deterministic ECMWF brings some showers to the
North Bay next Friday, but ensemble guidance not so much. Forecast
is dry for now. The trough will at a minimum bring cooler
temperatures.

&&

.AVIATION...as of 11:04 AM PDT Saturday...For the 18Z TAFs. VFR
conditions prevail with mostly clear skies, as high pressure
builds over the eastern Pacific. HZ is reported at some area
terminals and observed on webcams, which may cause tempo
reductions in vis, but mainly VFR. Marine stratus is observed on
satellite imagery, mostly well offshore. Light winds becoming
breezy onshore this afternoon. As winds diminish this evening,
models project more low cloud development along the coast,
particularly around Monterey Bay, where IFR conditions are
forecast, but VFR elsewhere.

Vicinity of KSFO...Moderate onshore winds near 10 kt, becoming
breezy with gusts possible up to 25 knots in the afternoon. Winds
diminish at night as VFR conditions continue. A few low clouds may
develop around the bay in the early morning hours.

KSFO Bridge Approach...Similar to KSFO.

Monterey Bay...Skies have cleared over land with just a thin band
of clouds well off the coast. VFR conditions expected into late
tonight. Breezy onshore winds this afternoon. IFR conditions
possible tonight as stratus builds over the bay and moves onshore,
likely around midnight or soon after. Clouds burn off mid-morning
Sunday.

&&

.MARINE...as of 10:37 AM PDT Saturday...Strong northwest winds
with near gale force gusts in the northern outer waters will
persist through the weekend, with widespread  steep, hazardous
seas. Winds near the immediate coastline are  forecast to be
generally lighter, but still strong near coastal jets. Prevailing
wave heights over 10 feet at periods of 9 to 11  seconds through
the weekend will keep hazardous seas, particularly for smaller
vessels. Winds are expected to restrengthen early  next week.

&&

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

&&

$$

PUBLIC FORECAST: MM
AVIATION: Lorber
MARINE: Lorber

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