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

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FXUS66 KMTR 261547

Area Forecast Discussion
National Weather Service San Francisco Bay Area
847 AM PDT Sun Jun 26 2022

.SYNOPSIS...Dry and generally seasonal weather conditions expected
through the forecast period. Continuing very warm to hot days farther
inland areas early this week, then gradual cooling. A marine layer
will continue along the coast with associated low clouds and patchy
fog progressing locally inland night and morning hours.

&& of 08:43 AM PDT Sunday...June gloom in full
effect this morning per visible satellite. A classic set up for
stratus covering the coast and inland valley. The depth of the
marine layer/stratus deck is also resulting in patchy fog and
drizzle. Latest satellite imagery however does show some thinning
on the edges/inland areas of the stratus deck. Expect this trend
to continue through mid-morning as clouds erode and roll back to
the immediate coast. The bigger weather story over the next two
days continues to be the temperatures. There will likely be a
large spread of temperatures with far interior locations reaching
hot to very hot conditions. The hottest locations will be outside
of any marine influence. An example of this would be far interior
San Benito county and portions of the southern Salinas Valley. A
Heat Advisory remains in effect for this location through 10 PM
Monday. There will be minor relief in the southern Salinas Valley
at night, but daytime temperatures will still approach or exceed
triple digits.

More details on the marine layer see below...


.PREV of 4:17 AM PDT Sunday...Nearly ideal conditions
exist for maritime stratus and fog this morning, nearly flat north-
south/south-north juxtaposed pressure gradients and winds while
SFO-SAC is 2.0 mb supporting onshore breezes this morning. Stratus
and fog continue to anchor in and onshore breezes are advecting
stratus and fog inland across the Bay Area especially the North
Bay while stratus and fog are also filling in across the San
Francisco Bay, to the south stratus and fog continue to steadily
filter in along the 101 corridor in the Salinas Valley. The marine
layer depth varies from 1,500 feet Bodega Bay to 1,000 feet Fort
Ord. A 590 decameter 500 mb height closed high is located approx
200 miles southwest of Point Conception, a 500 mb ridge extending
to the north is compressing the marine layer a little more at Fort
Ord compared to Bodega Bay. Metar observations at KHAF and KMRY
report 1 mile or less in fog early this morning. Recent meso-scale
and in some cases global model output also forecast a few patches
of light coastal drizzle; no reports as of yet of light measurable
precipitation, will monitor and add drizzle in the forecast if

The aforementioned 500 mb ridge extends northward today and
tonight enhancing the marine layer lower level temperature
inversion. Stratus and fog over land will mix out today under
diurnal warming while onshore breezes continue becoming locally
gusty as onshore gradients increase again, similar to Saturday
afternoon and evening. Challenging forecast regarding forecast
highs, there`s potential for large ocean to well inland temperature
variations again during peak heating today. Morning temperatures at
elevation across interior Monterey and San Benito counties are in
the 60s/70s, however cooler air in the 50s including some upper 40s
in the valleys have also made good inroads this morning as well.
Closely monitoring moderate to high heat risks with main focus of
concern across interior portions of Monterey and San Benito counties
today and Monday. A Heat Advisory remains in effect for southern
Salinas Valley and interior San Benito county until 10 pm Monday.
Good onshore breezes may possibly help mitigate warmest temps on the
northern edges of the heat advisory today and Monday. Forecast highs
today, Monday and Tuesday were edged a little lower mainly nearest
the coast and bays. By Tuesday a more widespread cooling trend will
develop as westerly winds surface and aloft help push the thermal
ridge aloft inland, extending an increasingly more robust magnitude
of maritime cooling farther inland.

There`s good model agreement that through late June a progressive
west to east mid-latitude pattern will then in early July bring
one of the (active) northern hemipshere`s longwave troughs with
below normal 500 mb heights and robust northwest surface winds to
the CA coastal waters and coastline. The trough becoming stationary
during early July as the northern hemisphere pattern decreases to
a five wave pattern. Strong mid-latitude drying influences precluding
chances of precipitation it seems here in our cwa, as it would be
extremely rare in any case to have a mid-latitude system bring
precipitation to the Bay Area during the driest month of the year
climatologically. However, it bears watching and specifically
need to watch the strength of the core of the 500 mb low as it
nears northern California during this time. This system like we
see with late cool season lows at least has the potential to disrupt
possibly fully mixing out the marine layer; it depends on the strength
and proximity of the trough.


.AVIATION...As of 4:30 AM PDT Sunday... For the 12Z TAFs. Stratus
has filled into low lying areas overnight, covering a good portion
of the cwa. The entire SF Bay is covered in this shallow stratus
layer, but still VFR conditions prevail at KSFO/KOAK. TEMPO
included for possible BKN/OVC low clouds spillage before sunrise.
Stratus even making its way down the Santa Clara Valley, so tempo
for brief cigs included for KSJC as well. Terminals close to the
coast remain LIFR through 16-17z this morning. Generally light
westerly winds expected today but will be breezy near coastal
gaps and in valleys. Stratus returns this evening for Monterey
Bay terminals. So far looking into tomorrow, models not showing
widespread stratus coverage like what we saw tonight.

Vicinity of KSFO...Stratus has filled into the bay but KSFO/KOAK
remain VFR for now. SCT low clouds at 700 feet at KOAK but tempo
included for IFR cigs for the remainder of the early morning.
KSFO could also see some stratus enter into the terminal from the
NE in the coming hours. VFR expected after 16-17z today. Winds
will be breezy, similar to yesterday, with NW winds around
10 to 20 kt. Low clouds return late today into Monday morning.

KSFO Bridge Approach...Low clouds hovering over a good portion of the
Bay until 17z. May be lingering low clouds near San Mateo bridge
later in the morning after 17z that could impact visual approach.

Monterey Bay...LIFR cigs holding steady this morning with shallow
stratus deck. Clearing will be around 16z this morning and VFR
will prevail. Similar setup later today with moderate onshore
flow and cigs rolling back in this evening and lasting through the

&& of 2:38 AM PDT Sunday...Dense fog in some areas this
morning over the waters. Calm winds persist into Monday over most
areas, with stronger winds of 20 to 30 kts in the coastal jet
near and south of Point Sur. Locally gusty winds are expected
through the Golden Gate gap and toward Angel Island in the
Northern San Francisco Bay during the afternoons. Sea state is
mostly wind driven with easing wind waves of 3 to 4 feet from the
northwest at 7 to 8 seconds, in addition to a longer period
southwest swell at 14 to 15 seconds.


     .Tday...Heat Advisory...CAZ516-518
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 3 PM
             SCA...SF Bay from 3 PM



MARINE: McCorkle

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