339
FXUS66 KMTR 040411
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
911 PM PDT Wed Jul 3 2024

...New UPDATE, MARINE...

.SYNOPSIS...
Issued at 257 PM PDT Wed Jul 3 2024

Extremely hot conditions continue through at least Wednesday of
next week. Heat products have been extended, Red Flag Warnings
have been extended, Fire Weather Watch has been upgraded to a Red
Flag Warning for Monterey and San Benito.

&&

.UPDATE...
Issued at 907 PM PDT Wed Jul 3 2024

It was another HOT day across the interior with a couple of records
broken at Livermore and San Rafael (see below). However,
temperatures were slightly cooler across the board minus far
interior portions of the East Bay and interior Monterey and San
Bentio counties. Low clouds have worked their way northward up the
Big Sur coast and most recently started to impact the Monterey
Peninsula. It is unclear how far north they will go and whether or
not the will push much inland in the Salinas Valley (or any other
coastal adjacent valleys).

Tonight, temperatures will lower into the mid 50`s to lower 60`s in
coastal areas and cooler interior valleys, lower 70`s in the warmer
valleys (such as the southern Santa Clara Valley), and mid 60`s to
low 80`s in the higher terrain. This will provide minimal overnight
relief from today`s heat.

...RECORD HIGH TEMPERATURES WEDNESDAY, JULY 3, 2024...

LOCATION                    HIGH          PREVIOUS RECORD
---------------------------------------------------------------
SAN RAFAEL                  100           99 IN 2001
LIVERMORE                   110          109 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.

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 257 PM PDT Wed Jul 3 2024

Guess what? Its another AFD about very hot temperatures!
But not just that, Red Flag conditions as well. Let`s list the
changes up front and center:

-Excessive Heat Warning has been extended through 11pm Wednesday
 July 10th.
-Heat Advisory for northern Monterey Bay, Northern Salinas Valley,
 and SF Bay shorelines has been extended through 11pm Wednesday
 July 10th.
-Red Flag Warning for Interior North Bay Mountains and East Bay Hills
 has been extended through 9 PM Saturday July 6th.
-Fire Weather Watch has been upgraded to a Red Flag Warning for
 the mountains of Monterey and San Benito Counties, and the
 southern Salinas Valley for very low RH values, and critically
 dry fuels.
-Coastal Flood Advisory has been extended through 5am Friday July 5th
 for high astronomical tides and possible flooding of low lying
 areas around the SF Bay.

Now let`s dig in:

While you`re probably sick of hearing it, it can not be emphasized
enough how warm things are going to be over the stretch of a week.
Not just a few days. A week. As it currently stands, we are
officially on Day 2 of this heat wave, if you`re going by the
guidance of how long the Excessive Heat Warning persists. As cluster
analysis continues to show a general consensus of this ridge
sticking around even through day 9, hot temperatures are expected to
continue with high temperatures of 100-105 continuing through at
least next Wednesday for interior areas. 850 mb temps continue to
trend on the very warm side, with this mornings 12Z KOAK sounding
showing 850 mb temps at 26.4 degrees Celsius (79.5 degrees
Fahrenheit). A glance at models continues to show 850 mb temps
exceeding this 26 C mark through at least early next week. Continued
and building high pressure may also lead to some hazy skies the next
few days as particulate matter including smog, smoke from wildfires
and fireworks, and even dust will be trapped near the ground. For
questions regarding air quality forecasts, reach out to your local
air quality district.

Aside from the hot daytime temps, overnight lows will also
continue to provide little to no relief, ESPECIALLY in thermal
belted areas where overnight lows likely will not dip below the
mid 80s. In lower elevations, overnight lows are not likely to dip
lower than the mid 70s. This is an ultra-marathon, not just for
our bodies, but our pets and livestock, and infrastructure too.
Without the overnight relief, our bodies do not experience the
normal cooling and respite they normally would, therefore
increasing the demand on our respiratory and circulatory systems
to help keep up cool. With that being said, it is very likely that
we will see a number of heat- related fatalities throughout this
event, not just from homeless populations who may not be able to
escape the lethal heat, but from housed people too that perhaps
lack air conditioning (which many houses in the Bay Area do lack
this!), or perhaps simply cannot afford to turn it on, even if
they have it.

It is imperative to take measures to protect yourself, loved ones,
and animals during this extreme heat. Given that tomorrow is
Independence Day, a holiday in which many activities take place
outdoors (parades, picnics, BBQs, community gatherings, fireworks
displays), extra caution is urged. For areas of Extreme Heat Risk,
consider suspending outdoor events or modifying them to take place
indoors in an air conditioned environment. Clearly, an event such as
a parade cannot be moved inside, but modifications can be made to
events to make it safer for everyone, be it moving it to a time much
earlier in the morning when its still "cool" (though again, temps
will likely already be in the 90s come the 9-10am hour), or perhaps
if you can, moving the event indoors if possible, and if you cannot,
taking into consideration canceling the outdoor event. Aside from
these measures, there are many other things you can do to protect
yourself, including staying hydrated by drinking HYDRATING beverages
such as water or sports drinks with electrolytes, and avoiding
DEHYDRATING beverages such as alcohol and caffeine-laden drinks. A
few other heat safety tips:

-Stay inside in an air conditioned environment between 10am and 7pm.
-Suspend unnecessary outdoor activities during the extreme heat,
 but if you must be outdoors, take frequent breaks in the shade
 or AC and drink cool water.
-Know the signs and symptoms of Heat Exhaustion vs. Heat Stroke! Heat
 Stroke can be deadly if not treated immediately by a medical
 professional. Call 911 if you suspect someone is suffering from
 Heat Stroke.
-Wear a lifejacket, swim near a lifeguard, and check conditions before
 entering the water if going to a river or ocean to cool off.
 Rivers and the ocean are extremely cold, and Cold Water Shock can
 turn into paralysis and drowning if you are not careful.
-Use a cool and damp towel on your body if you do not have AC and
 are feeling hot. Or, take a cool shower or bath.

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 257 PM PDT Wed Jul 3 2024

By now you know the heat extends into the longer term,
into next week, so we`ll focus on Fire Weather in the long term,
seeing as those concerns extend over part of the weekend.

With the extension of Red Flag Warnings this morning, and the
upgrading of the Fire Weather Watch into a Red Flag for San Benito
and Monterey Counties, conditions will be ripe for fire growth
should a spark ignite something. The decision was made to extend
the RFWs and to upgrade the Watch based off of very low RH values
(generally dipping below 15% RH), critically dry fuels (ERC values
exceeding or coming extraordinarily close to exceeding the max
moving average for a number of regions), in addition to the final
component of winds. Now you might be scratching your head at that
final component. Where are the breezy, gusty winds you speak of?
Well, with fuels this dry, and RHs down into single digits in some
areas for daytime minimums, we don`t necessarily need winds to be
breezy and gusty. At the bottom tier of the decision matrix, with
daytime min RHs into the single digits, and nighttime max RHs in
the teens to low 20% range, we only need winds about 6-11mph
sustained to warrant issuing a Red Flag Warning. As it currently
stands, we are forecast to meet those criteria, especially within
Monterey and San Benito counties, and the East Bay Hills. North
Bay mountains are a bit more marginal in regards to the RH
recoveries, but nonetheless are forecast to meet the criteria.
Additionally, fuels will continue to dry as we persist through
this very long period of extraordinarily hot and dry weather as
the ridge continues to build. Conditions are dangerous, and we
urge extreme caution. Please rethink the use of any fireworks this
year, including the safe and sane, or even those seemingly-
innocuous sparklers and pop-its. Perhaps consider not lighting
them off at all this year, and instead enjoy a professional
display in your community, or even on TV. Its not worth the risk.
Don`t Be the Spark! Additionally, check those chains and per our
recent social media post: Keep those butts in the window! Don`t
let your chains drag while towing, and do not toss cigarette butts
out the window. Additionally, do not operate machinery or
vehicles over dry vegetation.

As a final note on this long AFD, none of this is meant to
"fearmonger" or incite worry. Rather, we simply want people to be
as safe as possible throughout the coming days. We are tasked with
the protection of life and property, and we would be failing to
accomplish this without mention of the risks and hazards that lie
ahead, as well as the facts. Heat is the number one weather-
related killer across the nation. We will likely come to learn of
casualties in the coming weeks and days attributed to the heat.
Have fun, and enjoy the holiday as well as these summer days. Just
be safe, be careful, and make modifications as necessary to keep
yourselves and others safe. We will be doing the same!

&&

.AVIATION...
(00Z TAFS)
Issued at 419 PM PDT Wed Jul 3 2024

Clear skies and VFR across the board this evening as high pressure
dominates. Areas of fog will develop along the coast overnight,
but areas further inland are likely to remain clear. Light winds
with not much impact overnight into the morning hours Thursday.
After sunrise tomorrow, chance of reduced slant range visibility
due to wildfire smoke.

Vicinity of SFO...High confidence that VFR will prevail through
the TAF period. Winds become light this evening into the morning.
NW/W winds increase again Thursday afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Confidence is
low that CIGs and low vis will occur. Will continue to monitor
for any updates needed to the TAFs.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 907 PM PDT Wed Jul 3 2024

Light moderate winds continue into the weekend with possible
gusty and strong winds in the northern outer waters that will pose
hazardous to small crafts into tonight before easing. Waves start
to diminish Thursday morning, bringing relatively calm conditions
over the waters into Friday.

&&

.FIRE WEATHER...
Issued at 257 PM PDT Wed Jul 3 2024

Northerly winds are gusting in the 20-30 mph range
mph overnight, with Mt. St Helena gusting as high as 64 mph and
Mount Diablo at 54 mph early this morning. While winds will begin
to diminish over the next few days, these RFW extend through 9 PM
Saturday evening due to the critically dry conditions. In fact,
10 and 100 hour fuels are near historic levels in the Santa Cruz,
Diablo and North Bay Mountains in regard to the energy release
component going into the weekend. In addition to the hot, dry
weather, the 4th of July Holiday may lead to new starts from stray
fireworks. Further south, things start to dry out more this
weekend.

&&

.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.

&&

.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 Wednesday for CAZ502>504-
     506-510-512>518.

     Red Flag Warning until 5 AM PDT Friday for CAZ502-503.

     Red Flag Warning until 9 PM PDT Saturday for CAZ504-512-515.

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

     Red Flag Warning from 9 AM Friday to 9 PM PDT Saturday for
     CAZ516>518.

PZ...Small Craft Advisory until 3 AM PDT Thursday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

UPDATE...RGass
SHORT TERM...AC
LONG TERM....AC
AVIATION...Behringer
MARINE...Behringer
FIRE WEATHER...RGass
BEACHES...Flynn

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