554
FXUS66 KMTR 030854
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
154 AM PDT Wed Jul 3 2024

...New SYNOPSIS, SHORT TERM, LONG TERM, FIRE WEATHER, BEACHES, CLIMATE...

.SYNOPSIS...
Issued at 1224 AM PDT Wed Jul 3 2024

Extreme heat will continue for inland areas and higher elevations.
Triple digit afternoon temperatures are expected into early next
week. Please take it easy, we are still in the early stages of
this prolonged heat wave.

&&

.SHORT TERM...
(Today and tonight)
Issued at 1224 AM PDT Wed Jul 3 2024

It`s almost 1 AM as I type this and it`s still 80 degrees in San
Jose. Weather stations in the thermal belt around 1,500 ft are
still in the low 90s. This is 5-10 degrees higher than expected on
even the high-resolution short term models. If this trend holds
through sunrise, the warm start will lead to numerous daily
records being broken Wednesday. The NBM 50th percentile max
temperature strategy broadly panned out yesterday, and was used
again for the forecast this morning. One notable bust was Santa
Cruz, where we forecast mid 80s, but they never got out of the 60s.
This is evidence that the marine layer, while shallow, is still
having a profound cooling effect on coastal cities. This natural
air conditioning will continue along the coast today, but with
building high pressure, the marine layer will compress below 500
ft and won`t extend as far inland. If you live along the coast,
enjoy the nice weather, but before you complain that we are
overy-hyping the heat wave, remember that it was 108 degrees in
Concord yesterday.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 1224 AM PDT Wed Jul 3 2024

July 4th is in the middle of this heat wave. It will be clear and
hot, unless you can make it to the coast. With a shallow marine
layer, there will be a big difference across the Bay Area
microclimates. As an example, downtown San Francisco will be in
the mid 80s, while Ocean Beach will remain in the mid 60s. Winds
will mostly remain gentle to moderate. Enjoy the day but stay
weather aware. Use caution in the heat or on the beach, and
please skip the fireworks this year. Wildfires will be easy to
start and quick to spread.

The lastest weather balloon found 850 mb temperatures have climbed
above 25C. This threshold is reached 1.8% of the time. More
interesting is the fact that the 850 mb temp now is expected to
remain above 25C through the end of next week. Nearly all members
of the ECMWF and GEFS ensembles keep a strong ridge in place that
very gradually slides east over the next week and a half. As such,
the confidence is high and increasing that this heat wave will
persist through the end of next week for inland areas. There may
be some slight relief after the weekend and inland temps may move
back in the double digits, but it`s not a big cool-down.
Additionally, the cumulative effect of this long heat wave will
make it hard to appreciate the modest relief in afternoon temps.
With no strong offshore winds expected, coastal areas will remain
more mild through this event.

It cannot be stressed enough that this is an exceptionally
dangerous and lethal situation. It may not seem so if you live
near the coast, but an event of this scale, magnitude, and
longevity will likely rival anything we`ve seen in the last 18
years for inland areas. Several days of temperatures well above
normal and little relief overnight will lead to compounding
effects among people and infrastructure, with the possibility of
numerous heat related fatalities and rolling black outs. Heat is
the number one weather related killer in the United States. By
this weekend, it is VERY LIKELY that we add to that statistic if
preparations are not taken seriously.

&&

.AVIATION...
(06Z TAFS)
Issued at 942 PM PDT Tue Jul 2 2024

VFR through the TAF period except for Monterey Bay. Winds light and
offshore tonight for most terminals, with a few VRB. High pressure
will continue to provide clear skies, though haze is thought to
obscure visibilities slightly in the afternoon and evening
tomorrow as pollution is trapped near the ground, and smoke
filters into the area from nearby wildfires. Onshore winds return
in the afternoon tomorrow but will be predominantly light.

Vicinity of SFO...VFR through the TAF period. Light easterly flow is
likely to develop in the morning Wednesday, but will turn to become
more NW and breezy into the late morning and early afternoon. Haze
will likely reduce visibilities in the area in the late afternoon
and early evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR persists through the early morning,
though stratus may trickle in bringing intermittent LIFR CIGs. With
the severe compression of the marine layer, and light offshore flow
expected overnight, there remains uncertainty as to whether CIGs
will actually form over KMRY and KSNS. The compression and light
offshore flow could be just enough to erode any stratus that begins
to form. Models do continue to indicate stratus forming over
terminals in the early morning Wednesday, but given the
aforementioned, confidence on CIG formation is low. However, should
CIGs form, confidence is high that they will be LIFR given the
severe compression from high pressure. That all aside, VFR returns

&&

.MARINE...
Issued at 841 PM PDT Tue Jul 2 2024

Fresh northerly winds continue over the outer coastal waters
today, with gale force gusts expected over the northern outer
waters through early Wednesday morning. As high pressure
strengthens and moves eastward, winds begin to diminish late
tomorrow night. Winds from late tomorrow night through the
weekend are expected to be predominantly gentle to moderate.
Portions of the northern outer waters may see peak wave heights
between 12-16 feet through the late afternoon of Wednesday.

&&

.FIRE WEATHER...
Issued at 1224 AM PDT Wed Jul 3 2024

Red Flag Warnings remain in effect for high elevations of the
North Bay, East Bay, and the Santa Cruz Mountains. These RFW
extend through 5 AM Friday, including the 4th of July holiday.
Fuels will continue quickly curing through the weekend. In fact,
10 and 100 hour fuels are near historic levels in the North Bay in
regard to the energy release component going into the weekend.
The same fuels in the Diablo Range and Santa Cruz Mtns aren`t far
behind. Further south, things start to dry out more this weekend.
A Fire Weather Watch is in effect for the Santa Lucia Range,
Interior Monterey and San Benito county, and the Southern Salinas
Valley from Friday morning to Sunday night.

&&

.BEACHES...
Issued at 1224 AM PDT Wed Jul 3 2024

Beaches will be a popular destination over the Holiday and as one
of the few places to escape the oppressive inland temperatures.
Fortunately the waves are relatively low energy, but that doesn`t
alleviate all beach safety concerns. Ocean temperatures are in
the mid-50s. This cold water may catch some off-guard. Cold water
shock can set in very quickly. Wear a life jacket, dress
appropriately, limit time in the water, swim near a lifeguard and
follow their instructions.

&&

.CLIMATE...
Issued at 1224 AM PDT Wed Jul 3 2024

This heat wave will continue to break daily records. Here`s a look
at locations that tied or beat their daily record on Tuesday, July
2nd.

LOCATION                    HIGH          PREVIOUS RECORD
---------------------------------------------------------------
SAN JOSE                    102   (TIED)  102 IN 1970
SAN RAFAEL                  103           101 IN 1991
KENTFIELD                   103           101 IN 1991
SANTA ROSA                  105           103 IN 1970
OAKLAND                     90            89  IN 2001

These data are preliminary and have not undergone final quality
control by the National Centers for Environmental Information.
Therefore, these data are subject to revision. Final and certified
climate data can be accessed at www.ncei.noaa.gov.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 11 PM PDT this evening for CAZ006-
     506-508.

     Heat Advisory until 7 PM PDT Thursday for CAZ006.

     Excessive Heat Warning until 11 PM PDT Tuesday for CAZ502>504-
     506-510-512>518.

     Red Flag Warning until 5 AM PDT Friday for CAZ502>504-512-515.

     Heat Advisory until 11 PM PDT Tuesday for CAZ508-528-529.

     Fire Weather Watch from Friday morning through Sunday evening
     for CAZ516>518.

PZ...Small Craft Advisory until 3 AM PDT early this morning for Pt
     Arena to Pt Reyes 0-10 nm.

     Gale Warning until 9 AM PDT this morning for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...AC
MARINE...AC

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