339
FXUS66 KMTR 071649
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
949 AM PDT Sun Jul 7 2024

...New UPDATE...

.SYNOPSIS...
Issued at 1236 AM PDT Sun Jul 7 2024

Day 6 of the inland heat wave. The peak of the event is finally
behind us and some minor relief is on the way this week before a
more substantial cool-down next weekend.

&&

.UPDATE...
Issued at 944 AM PDT Sun Jul 7 2024

No update to the forecast this morning. The Excessive Heat Warning
remains in effect until Wednesday morning for most of our interior
locations, with Heat Advisories still in effect for some locations
closer to the coast. The Heat Advisory for the low lying areas of
Santa Cruz was cancelled. Also, all Red Flag Warnings have
expired, however the national hazards map still has them
displayed. The issue is being worked on at the national level.

&&

.SHORT TERM...
(Today and tonight)
Issued at 1236 AM PDT Sun Jul 7 2024

ACARS data from Oakland flights are showing the 850 mb temperature
is 31C. The highest 850 mb temperature ever observed from the
Oakland weather balloon is 31.0C. This means we are experiencing
the hottest low level heat since records began 75 years ago.
Inland areas reached triple digits yesterday with a few over 110.
Higher elevations are seeing some of the hottest daily max and
min temps on record. For example Pinnacles National Park reached
116 degrees yesterday (all time record 117 9/6/20), and Mallory
Ridge (north of Livermore @ 1948 ft) only got down to 90 Saturday
morning before jumping back up to 106 in the afternoon.
Fortunately onshore winds and a shallow marine layer are keeping
coastal areas cool.

As the ridge axis moves across California, temperatures will begin
to cool a bit Sunday. The only record we are threatening is at
King City (105 forecast). Otherwise, most inland areas will stay
out of the 100s today. Higher elevations are still seeing very
warm conditions, but they will also begin to cool a few degrees
Sunday. Coastal areas will be much cooler (similar to yesterday)
with marine layer clouds breaking in the afternoon and returning
in the evening.

&&

.LONG TERM...
(Monday through Saturday)
Issued at 1236 AM PDT Sun Jul 7 2024

The cool-down will continue through Tuesday as the ridge continues
to slide east. While this is certainly welcome, it is not a
drastic improvement. To put it in perspective, the 850 mb temp is
currently in the top 99.99% (30.2 C) of historical observations.
We are anxiously awaiting it to drop back to the the 98% (25 C) by
Tuesday. We are still going to be well above average this week with
inland areas remaining in the 90s. By Wednesday, the cooling
trend flattens, and temps may tick back up a few degrees Wed-Fri
before a more substantial cool-down arrives this weekend.

This heat wave has been going for 5 days now and we are just now
getting on the back nine. The warm mornings and back-to-back
record breaking temperatures can cause cumulative effects that
make the situation more dangerous. 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. You can put your
 cellphone/wallet or even your shoe in the back seat as a reminder.
-Ensure pets and livestock have access to shade and water.

&&

.AVIATION...
(12Z TAFS)
Issued at 448 AM PDT Sun Jul 7 2024

Mix of VFR and LIFR conditions across the board. Night Fog shows
stratus moving inland towards STS, APC, and OAK with stratus already
located at MRY and SNS. Stratus is expected to reach STS, APC, and
OAK shortly (between 12-13Z) with five minute obs at all three
airports showing low level clouds already present. Elevated fog
potential remains for STS, MRY, and SNS with visibility most likely
to drop between 12-16Z. For OAK and SFO - stratus has been slightly
slower to filter into the SF Bay than previously expected. Stratus
arrival has been pushed back for SFO and OAK with moderate
confidence that stratus will reach SFO. Onshore flow continues
through the period with moderate winds persisting into the evening
before weakening overnight.

Vicinity of SFO...VFR becoming IFR during the early morning hours.
Low to moderate confidence that stratus will reach SFO. Stratus has
been filtering into the SF Bay slower than originally forecast
resulting in beginning of IFR conditions being pushed back several
hours. Ensemble guidance continues to indicate a brief period of IFR
CIGs but confidence remains low to moderate given the slower stratus
arrival time. Onshore flow persists through the period with
moderate, gusty winds returning during the afternoon before
diminishing overnight. Ensemble guidance indicates stratus is likely
to return tomorrow night but low confidence on the exact timing.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR conditions continue through mid to
late morning before VFR returns briefly during the
afternoon/evening. Low to moderate confidence that visibilities will
degrade significantly this morning. For now leaning towards minimal
visibility interruptions, however, elevated fog potential does
remain with 12-16Z the most likely time for larger dips in
visibility to occur/for fog to form. Onshore flow continues through
the TAF period with moderate winds expected during the day before
lighter, more variable winds return overnight. Stratus is expected
to return by the late evening with CIGs expected to quickly
transition from IFR to LIFR.

&&

.MARINE...
(Today through Friday)
Issued at 448 AM PDT Sun Jul 7 2024

High pressure continues over the Pacific Ocean with gentle to
moderate northwest winds persisting into the early work week.
Fresh  to the occasional strong gusts will briefly develop over
the  northern outer coastal waters Monday before diminishing into
Tuesday. Widespread fresh to strong northwest winds return across
the coastal waters by mid-week. Significant wave heights will
build to 10-14 feet in the outer waters beginning Wednesday.

&&

.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.

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

&&

$$

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

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