387
FXUS66 KMTR 031722
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1022 AM PDT Wed Jul 3 2024

...New AVIATION, MARINE...

.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.

&&

.UPDATE...
Issued at 1005 AM PDT Wed Jul 3 2024

It`s a bit past 9am, and temperatures across
the region are running on average anywhere from 3-7 degrees warmer
than this same time yesterday. A few spots in the South Bay are even
10-11 degrees warmer than this same time yesterday with current
temps sitting in the low 90s. Read that again. 9am, and temperatures
are in the 90s in the South Bay. But wait! They`re in the 90s in the
East Bay, central San Benito county, and the eastern portion of Napa
county bordering that of Yolo and Solano counties too! Elsewhere but
for the immediate coast, temperatures are well into the upper 80s.
Needless to say, its going to be another very hot day across our
region. Keep in mind, this is JUST day 2 of an extraordinary heat
wave (interior regions reaching into 95-100+ degrees daytime highs)
that keeps going through at least Tuesday of next week, and
potentially even Wednesday. We`re not just looking at a marathon,
but an ultra-marathon at this point. Its one thing to have a stretch
of very hot days, its another to have stretch of very hot days AND
little to no overnight relief. This is the part that can be most
taxing on our bodies: The normal relief we might get from cool
overnight temperatures just isn`t quite there, therefore forcing our
bodies to keep working harder to keep us cool. But not just our
bodies; our infrastructure too.

So please, take it easy, take it safe, and stay cool however you
can. We`ve seen a lot of comments and replies downplaying the
severity of the heat we are expecting, and even accusing ourselves
and other offices of "fearmongering". Make no mistake, this heat
wave is extreme, and will likely be deadly as the days of extreme
heat continue to accumulate, especially given that there are many
homes throughout the Bay Area that do not have air conditioning
installed. We are not here to fearmonger, but rather to inform you
all to the best of our abilities and to protect life and property
during this extreme heat event. We want everyone to be safe and
informed.

This all aside, we are examining the need to extend Red Flag
Warnings for critically dry conditions that persist through the
weekend. All for now.

&&

.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
over-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...
(18Z TAFS)
Issued at 1021 AM PDT Wed Jul 3 2024

Satellite shows clear skies across the region with some stratus off
the coast traveling northward. The marine layer has compressed under
the high pressure systems influence. This will increase the chances
for some low visibility and low ceilings near the coastal sites.
Higher confidence that only Monterey terminals may be effected, but
chances still remain low. With some current fires, there is a chance
for haze near the terminals. Otherwise, expect VFR to prevail
through the TAF period for all terminals. Onshore winds will become
moderate to breezy this afternoon before becoming variable and light
tonight.

Vicinity of SFO...High confidence that VFR will prevail through
the TAF period. NW/W winds will become breezy this afternoon up to
12 knots. Winds become light this evening into the morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Confidence is
low that lower CIGs and visibility will occur but models suggest
LIFR conditions over night. Will continue to monitor for any updates
needed to the TAFs.

&&

.MARINE...
(Today through Monday)
Issued at 1021 AM PDT Wed Jul 3 2024

  Gentle to moderate winds continue into the weekend, with
possible gusty and strong winds in the northern outer waters that
will  pose hazardous to small crafts through today. Portions of
the  northern outer waters may see peak wave heights between 11-16
feet through the late afternoon as well. Waves start to diminish
Thursday morning, bringing calm conditions over the waters.

&&

.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 5 AM PDT Friday 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 Thursday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...SO
MARINE...SO

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