386
FXUS66 KMTR 070608
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1108 PM PDT Sat Jul 6 2024

...New AVIATION, MARINE...

.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 849 PM PDT Sat Jul 6 2024

Another record-breaking day for Livermore and King City and
thankfully we are past the peak heating of this event. We are also
seeing some slight relief in fire concerns, allowing us to expire
the Red Flag Warning. However fuels are still dry, and humidities
in the interior are still low, so continue to be fire weather
aware. Temperatures will cool slightly in the next few days, but
will still be hazardous. Be sure to keep yourselves safe from the
heat!

- Murdock

&&

.SHORT TERM...
(This evening through Sunday)
Issued at 1257 PM PDT Sat Jul 6 2024

Today will mark the hottest day of the heat wave for most
locations across our area. Some of our higher elevations were
already in the 90s around 9AM this morning. The 12z KOAK sounding
measured the 6th highest H85 temperature of 30C with a chance of
breaking the all-time record this evening, with HiRes guidance
indicating around 31C around launch time. Red Flag Warnings remain
in effect for the Santa Cruz Mountains, North Bay Interior
Mountains and East Bay Hills until later this evening, as RH
values continue to be in single digits in some spots. The heat
backs off slightly tomorrow, but still well within Excessive Heat
Warning and Heat Advisory criteria.

A southern surge of low stratus can be expected again tonight as
the ridge axis continues to slowly pivot to the east of the coastline
tonight and tomorrow. Overnight lows into tomorrow morning will
also start to decline as we get on the other side of the peak
heat, with lows around our area generally 3-5 degrees cooler than
what we saw early this morning.

Please read below for tips on how to continue to beat the heat at
the end of the long term discussion.

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 1257 PM PDT Sat Jul 6 2024

Temperatures will continue to gradually trend downward but still
remain above normal through most of the extended forecast.
However, using the previously noted KOAK H85 temp as a marker, by
Tuesday evening its expected to be in the mid 20s instead of the
low 30s at that level. The cumulating impacts of the heat wave
will continue to be felt into the beginning of the work week. By
midweek the center of the persistent dome of high pressure will be
over eastern Nevada as upper level troughing works on the back
side of the ridge to lower H50 heights and thickness. As mentioned
before though, most areas inland and especially higher
elevations, will continue to see temperatures in the 90s and low
100s. All precautions to beat the heat should continue to be
taken:

Heat is the number 1 weather related killer in the United States.
Unfortunately lives will be lost during this heat wave. Follow these
tips to protect yourself, your loved ones, and your animals.

-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...
(06Z TAFS)
Issued at 1108 PM PDT Sat Jul 6 2024
Mix of IFR to LIFR expected tonight at most airports with only SJC
and LVK expected to remain VFR through the TAF period. Confidence is
increasing that stratus will return farther inland tonight with
elevated fog potential in the North Bay and Central Coast.
Visibility is expected to decrease overnight but confidence remains
low to moderate as to how far visibility will decrease at STS.
Guidance indicates elevated fog potential at STS but ensemble
guidance currently keeps visibilities above 1SM. Winds will remain
onshore at all stations through the TAF period with lighter
overnight winds anticipated to become more moderate by tomorrow
afternoon. Haze and smoke may be visible from terminals, but it is
not expected to result in a reduction in flight category.

Vicinity of SFO...VFR transitioning to IFR overnight. Moderate
confidence that IFR CIGs will develop overnight with low to moderate
confidence as to how far visibility will decrease. Ensemble guidance
shows a few models (NBM, GLAMP) with visibilities dropping to 2SM
but other models (HRRR) do not show visibilities decreasing much
below 6SM. For now, continuing the thinking that visibilities will
decrease but leaning towards visibility only decreasing to 4SM.
Onshore flow persists with light overnight winds becoming more
moderate and gusty during the afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR becoming VFR by late tomorrow morning.
Night Fog shows low level stratus blanketing MRY and SNS with
observations reporting CIGs at 300 ft. Elevated potential for fog
development and visibility is expected to decrease to a 1/2SM. LIFR
conditions will persist through the night and into tomorrow morning
before VFR conditions briefly return. Stratus and LIFR conditions
will return by tomorrow evening. Onshore flow persists through the
period with light overnight winds becoming more moderate during the
day.

&&

.MARINE...
(Tonight through next Friday)
Issued at 1108 PM PDT Sat Jul 6 2024

Surface high pressure over the Pacific Ocean will continue  to be
the dominating feature through the period. Northwesterly  breezes
will prevail through the period, increasing tomorrow  afternoon as
the pressure gradient tightens. Significant wave  heights begin to
build to 10-13 feet in the outer waters by  Wednesday.

&&

.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.

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

PZ...Small Craft Advisory from 3 PM Sunday to 9 AM PDT Monday for Pt
     Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Kennedy/Sarment
MARINE...Sarment

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