271
FXUS66 KMTR 061634
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
934 AM PDT Sat Jul 6 2024

...New UPDATE, FIRE WEATHER...

.SYNOPSIS...
Issued at 103 AM PDT Sat Jul 6 2024

Day 5 of the heat wave and triple digit temperatures will return
to inland areas this afternoon. A slight cool down begins Sunday,
but hot weather will continue through next week. Red Flag
Warnings remain in effect through Saturday night.

&&

.UPDATE...
Issued at 902 AM PDT Sat Jul 6 2024

Near term analysis - morning satellite imagery shows a shallow
marine layer had nosed its way inland overnight, but it`s already
retreating back the coast. Even though it`s retreating it won`t
disappear and will likely hug the coast through the day. As a
result, we`ll likely see some large temperature spreads from the
coast to the interior of 30-40 degs. Speaking of large
temperatures spreads, we`ve already seen some impressive
temperatures spreads in the vertical this morning too. Higher
elevations didn`t really cool off overnight as the marine layer
came in over lower elevations. Marin Headlands and Big Sur coast
are two great examples of temps in the 50s and 80/90s over nearby
higher elevations.

No update needed this morning...heat and fire are still the main
weather topics.

MM

&&

.SHORT TERM...
(Today and tonight)
Issued at 103 AM PDT Sat Jul 6 2024

A few daily records will likely fall this afternoon as the second
peak of this heat wave continues. Some inland areas will be in
the triple digits including Santa Rosa (101), Livermore (106),
and King City (105). Coastal areas will continue to enjoy nature`s
air conditioning as the marine layer fills up with stratus this
morning. These coastal clouds will come and go over the weekend,
but the cooler weather will remain.

Not much change to the short term forecast tonight as Saturday
continues to look like one of the hotter days in this prolonged
heat wave. The 850 mb temperature (measured at 27.5C at 00Z) will
likely peak today, with both the ECMWF and GEFS ensemble means
near 30C at 07/00Z. That benchmark has only been hit 6 times out
of roughly 56,000 weather balloon observations going gback to
1948. There`s even an outside chance (5% or so) that the all-time
record of 31C will be hit. Either way, we are continuing to deal
with historic heat, especially at higher elevations.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 103 AM PDT Sat Jul 6 2024

There is a little bit of good news in the long term forecast.
The strong, persistent ridge will finally slide east, with the
axis crossing California on Sunday. This will bring marginally
cooler temperatures. Inland areas will trade low 100s for mid to
upper 90s. Those slightly more mild conditions will then persist
through next week. I know everyone is looking for the end of this
heat wave, but the best we are going to get is a minor
improvement. While there won`t be many 100 degree thermometers
outside of southern Monterey and San Benito Counties (including
Pinnacles Nat`l Park), we are still way above seasonal averages.
In the short term section I mentioned the chance for 30C 850 temps
today. While we are glad to see that will start to come down next
week, it likely won`t drop below 24C until next weekend. 24C is
certainly better than 30C, but it`s still in the top 10% for this
time of year. So when will the heat wave actually end? There is
some indication that a cold front is possible next Friday. It`s
still early, and the models don`t yet agree, but there is hope.

This has been a long heat wave, and there is still much more to
come. Please continue to taking the following precautions to keep
yourself, family, friends and pets safe from the heat:

-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.
-Do not leave kids or pets in a parked car.
-Ensure pets and livestock have access to shade and water.

&&

.AVIATION...
(12Z TAFS)
Issued at 454 AM PDT Sat Jul 6 2024

Mix of VFR and LIFR conditions across the board. Night Fog shows
stratus moving inland over the Central Coast, the North Bay, and
into the San Francisco Bay. Current thinking is similar to earlier
with respect to OAK and SFO with IFR conditions expected to develop
at OAK but not at SFO. For APC, confidence is low to moderate that
low clouds will reach the airport. Guidance is better picking up on
some low clouds moving up the delta, eventually reaching APC, which
closely resembles the current Night Fog observations which increases
confidence slightly. LIFR conditions are expected to develop at APC
shortly and persist through midmorning. LIFR conditions at STS, MRY,
and SNS will persist through the midmorning before VFR conditions
return. Moderate onshore winds persist through the afternoon before
weakening overnight.

Vicinity of SFO...VFR through the TAF period. Moderate confidence
that stratus will not reach SFO with stratus expected to stay over
the eastern portions of the SF Bay/OAK. Moderate onshore flow
continues through the morning with gusts up to 25 knots possible
during the afternoon. Looking towards the end of the TAF period,
guidance indicates that stratus is likely to return overnight but
confidence in timing currently remains low.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR conditions persist through midmorning.
Stratus is expected to dissipate by mid-morning with model guidance
indicating that dissipation will occur between 16-18Z. Reduced
visibility is expected, with some potential for fog to develop,
through the early morning hours. Onshore flow persists with light,
variable winds strengthening and becoming more moderate during the
afternoon. Stratus is expected to return late this evening and
persist through the remainder of the TAF period.

&&

.MARINE...
(Today through Thursday)
Issued at 454 AM PDT Sat Jul 6 2024

High pressure continues through the forecast period. Winds
continue diminish with moderate to fresh northwest winds
persisting through the early work week. By midweek, northwest
winds strengthen with moderate to fresh sustained winds and strong
gusts possible across the coastal waters. Significant wave
heights will build to 10 to 13 feet by mid to late week.

&&

.FIRE WEATHER...
Issued at 920 AM PDT Sat Jul 6 2024

Just finished up coordination calls with agency fire partners and
neighboring offices. No updates needed for ongoing fire
headlines. Red Flag Warnings remain in effect for the North Bay
Interior Mountains, East Bay Hills and Santa Cruz Mountains until
9 PM Saturday. Red Flag Warnings are also in effect for the Santa
Lucia Mountains, San Benito County, and the Southern Salinas
Valley until 9 PM Saturday as well.

Marine layer brought some overnight relief for lower elevations,
but higher elevations (specifically Red Flag Locations) saw no
relief with temps in the 80s/90s and RH less than 30 percent.
Winds are breezy at times too. Needless to say critical fire
weather conditions.

While the Red Flag Warning is set to expire this evening with
weakening winds, lack of humidity recovery tonight over higher
elevations will lead to near critical conditions.

For Sunday, areas of concern will be focused away from the coast
with another hot and dry day. Area of greatest concern will be the
East Bay were afternoon gusty pass/gap winds combined with hot/dry
conditions will lead to isolated pockets of critical fire weather.
Not widespread enough for another Red Flag, but critical
nonetheless.

MM

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 11 PM PDT Wednesday for CAZ502>504-
     506-510-512>518.

     Red Flag Warning until 9 PM PDT this evening for CAZ504-512-
     515>518.

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

PZ...None.
&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Kennedy
MARINE...Kennedy

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