261
FXUS66 KMTR 021139
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
439 AM PDT Sun Jun 2 2024

...New SHORT TERM, LONG TERM, MARINE...

.SYNOPSIS...
Issued at 428 AM PDT Sun Jun 2 2024

Cooler temperatures continue into Monday with coastal stratus
developing overnight. Significant warming begins Tuesday with
moderate HeatRisk across the interior regions through Thursday.

&&

.SHORT TERM...
(Today and tonight)
Issued at 439 AM PDT Sun Jun 2 2024

Northwest to west winds are ushering in stratus along the coast
and inland. Observations show extensively higher humidity on west
winds across much of the Bay Area and north Central Coast as the
southernmost extent of a long plume of water vapor across the
Pacific Basin reaches the Pacific NW, and is also reaching our
forecast area however without sufficient dynamics expected to
result in rain here.

Wind gusts are still reaching 45-50 mph at Altamont Pass in the
East Bay at this hour. SFO Airport peaked 46 knots /53 mph/
yesterday evening. Winds are otherwise most places gradually
lowering overnight. It`s early meteorological summer (June-August)
and still astronomical spring and depending on the larger scale
pattern it`s not uncommon for winds to get strong and gusty here
in June; surface pressure gradients strengthen via surface
temperature contrasts land (warm-hot) vs coastal water sea surface
temps (cool to chilly). Winds again becoming gusty today into the
evening, then decreasing overnight into Monday morning. Daytime
highs 60s/70s coastside and bayside, farthest inland daytime highs
today in the 80s.

&&

.LONG TERM...
(Monday through Saturday)
Issued at 439 AM PDT Sun Jun 2 2024

A strong long wave trough exists over the North Pacific with an
extensive water vapor plume and sufficient dynamics for rain in
the Pacific NW. To the south of this, subtropical ridging over the
Pacific will strengthen during the week, noticeably beginning
Tuesday over our forecast area which will composite first with
weak long wave ridging over the western CONUS then strengthen mid
to late week. This will be in the wake of a splitting trough moving
eastward away from the Pacific NW reaching the east coast and moving
into/forming another long wave trough. The newly developing high
over the west will become nearly stationary, however there may
still be just enough eastward motion of the high to bring about a
southerly wind reversal here in our forecast area mid to late week.

Since there is good model agreement in the synoptic pattern aside
from strength differences mid to late week (the ECMWF is still
warmer to hotter with 850 mb temps over the Bay Area for example),
decided to issue a heat advisory for Tuesday and Wednesday for
inland areas. Northerly winds, downsloping and large scale
compressional warming will send temperatures upward quickly
Tuesday after sunrise (solar heating). Amplification and
additional compressional warming is quite likely mid to late week
since the high will become isolated (area of sinking motion) while
surrounded by low pressure systems (areas of upward motion).
Still a fair amount of uncertainty with the marine layer, as is
usual since it`s a very difficult thing to try to predict, given
the high level of water vapor as recently mentioned that is
forecast going into Tuesday-Wednesday. A moderate to strong ACV-SFO
pressure gradient (northerly wind) is forecast Tuesday-Wednesday
at least, there should be some drying due to downsloping across
Bay Area terrain and drying to due to compressional warming from
sinking air aloft. Stay tuned to the latest updates.

&&

.AVIATION...
(06Z TAFS)
Issued at 1201 AM PDT Sun Jun 2 2024

At this hour, winds are still gusty in the SF bay region, with SFO
reporting gusts upwards of 35 knots. SFO-SAC gradient continues to
show a 4.1 mb difference, indicating these strong winds will likely
last a bit longer into the night. Nonetheless, winds are expected to
ease ever so slightly, but, will likely remain at least breezy for
most locations. Many terminals are currently seeing IFR CIGs, which
models do not seem to agree with, with many suggesting MVFR
conditions instead. Current troughing would suggest CIGs being
higher, in MVFR territory, though this is not the case. It is
possible that sea salt lofted into the lower atmosphere by strong
winds could be contributing to the formation of these low clouds by
posing as a nuclei source, and thus permitting subsequent IFR
conditions.

All to say, a bit of an uncertain forecast tonight for
the TAFs, especially in regards to CIGs. Current confidence is that
CIGs will lift in the mid morning to become MVFR. Late clearing of
stratus is expected Sunday morning to early afternoon, with strong
and gusty onshore winds redeveloping.

Vicinity of SFO...Currently IFR. Moderate confidence in clouds
beginning to lift towards the mid morning hours of Sunday to become
MVFR. Winds will continue to gust overnight but as the SFO-SAC
gradient is forecast to decrease overnight to around 1.7mb, gusts
should begin to decrease below the 30 knot mark through the night.
However, into the late morning Sunday when VFR returns, the gradient
increases once more, inducing strong and gusty westerly winds once
more approaching the 33 knot mark. It is not out of the question
that gusts may go higher than this, though confidence on gusts
reaching higher is low.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...IFR conditions persist through the first
portion of the night, though slowly rise to become VFR by the mid to
late morning. Late clearing of stratus is expected, with VFR lasting
only a few hours in the afternoon of Sunday, and with SCT clouds.
Winds will increase out of the west to become breezy with gusts
nearing 20 knots. Stratus and low clouds return in the early evening
to bring MVFR conditions once more.

&&

.MARINE...
(Today through Friday)
Issued at 328 AM PDT Sun Jun 2 2024

Winds at this hour are fresh to strong, with gales having
subsided. Expect northwesterly winds to gradually diminish through
the day today to become fresh to moderate. As winds ease, wind
waves will decrease, and significant wave heights will gradually
lessen late tonight and into Monday, becoming 7 to 9 feet
generally.

&&

.CLIMATE...
Issued at 127 AM PDT Sat Jun 1 2024

Record high temperatures at the long term climate stations for
June 4th and 5th:

Station             June 4th             June 5th

Santa Rosa          98 in 1949           102 in 1926
Kentfield          101 in 1981           102 in 1926
Napa               102 in 1981           105 in 1903
Richmond            90 in 1955            86 in 1983
Livermore          105 in 1960           104 in 1926
San Francisco       92 in 1949            95 in 1883
SFO Airport         92 in 1955, 1949      89 in 1972
Redwood City       100 in 1981            97 in 2002, 1972
Half Moon Bay       71 in 1955            74 in 1958
Oakland downtown    96 in 1981            87 in 2002
San Jose            98 in 1904           100 in 1926
Salinas Airport     92 in 1949            87 in 1949
King City          102 in 1981, 1957     105 in 1926

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 8 AM Tuesday to midnight PDT Thursday night
     for CAZ503-504-506-510-515.

     Heat Advisory from 8 AM Wednesday to midnight PDT Thursday night
     for CAZ513-514-518.

PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this
     evening for Mry Bay-SF Bay N of Bay Bridge.

     Small Craft Advisory until 3 AM PDT Monday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt
     Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt
     to Pt Pinos 0-10 nm.

     Small Craft Advisory until 9 AM PDT Monday for Pt Pinos to Pt
     Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...AC
MARINE...AC

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