033
FXUS66 KMTR 062035
AFDMTR

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

...New SHORT TERM, LONG TERM...

.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...
(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...
(18Z TAFS)
Issued at 1152 AM PDT Sat Jul 6 2024

A strong lower level temperature inversion is present under
strong mid to upper level high pressure i.e. sinking, compressing
air, 925 mb (~ 2500 feet) and 850 mb (~5000 feet) level temperatures
on today`s 12z Oakland upper air sounding were 34.8 Celsius and
30 Celsius which tied 4th warmest at the 925 mb level and is 6th
warmest at the 850 mb level for the period of record since 1948.
Lower level temperatures within the temperature inversion will
hold either steady or warm a little more during the day. The SFO-SAC
pressure gradient (onshore wind) is weak at 1.3 mb however it does
prevail over the 0.7 mb ACV-SFO and 0.4 mb SFO-SMX pressure gradients
therefore allowing a marine layer intrusion of coastal fog, stratus
/LIFR-IFR conditions/, including patchy light drizzle this morning.
Inland it`s VFR.

Wildfire smoke and haze from the Lake Fire to our southeast may
lower slant range visibility aloft tonight and Sunday per recent
vertically integrated HRRR smoke forecasts. Northwest to west surface
winds will otherwise help keep good surface visibilities continuing
through today and this evening at least.

Recent HRRR and HREF output show coastal fog and stratus /LIFR-IFR/
redeveloping and moving locally inland tonight and Sunday morning,
otherwise VFR for inland terminals and stratus and fog mixing out
/VFR/ back to the coastline by late Sunday morning.

Vicinity of SFO...VFR. Light northeast wind becoming westerly and
increasing during the afternoon and early evening with gusts to
20 to 23 knots. Light west to northwest wind tonight and Sunday
morning, becoming west 15 to 20 knots Sunday afternoon.

SFO Bridge Approach...Similar to SFO. Slant range visibility likely
lowering by tonight and Sunday, lowest during sunset/sunrise.

Monterey Bay Terminals...Northwest winds over the coastal waters
is transporting fog and stratus /IFR/ conditions to the coastline
around the Monterey Bay. Still have late morning and afternoon
maximum mixing to erode stratus and fog back to VFR. Between early
and mid evening stratus and fog /LIFR-IFR/ will move back inland
for the overnight and Sunday morning then mixing out to VFR by late
Sunday morning and afternoon.

&&

.MARINE...
(Today through Thursday)
Issued at 1028 AM PDT Sat Jul 6 2024

High pressure continues through the forecast period. Winds
continue to 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...JM
LONG TERM....JM
AVIATION...Canepa
MARINE...Canepa

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