334
FXUS66 KMTR 020356
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
856 PM PDT Mon Jul 1 2024

...New UPDATE...

.SYNOPSIS...
Issued at 131 PM PDT Mon Jul 1 2024

Significant and extended warm up still slated to begin tomorrow
lasting into the weekend. Multiple days of dangerous temperatures
expected inland. Potential for well above average temps lasting
through the forecast period and into next week.

&&

.UPDATE...
Issued at 855 PM PDT Mon Jul 1 2024

Low level marine stratus over southern Monterey Bay is expected to
persist through late morning Tuesday, with mostly clear skies for
the remainder of the area overnight. See details below for the Red
Flag Warning beginning at 11pm tonight, that now includes the Santa
Cruz Mountains. Otherwise the forecast remains on track for a strong
dome of high pressure to begin exerting its influence across our
region tomorrow, and slowly migrate east through the remainder of
the extended forecast. The highest temperatures for some locations
inland are forecasted for tomorrow and Wednesday, but that does not
mean the impacts of this event end after Wednesday. As the heat
builds and continues well into next weekend, so too do the hazards
associated with it to vulnerable people and communities. Also, we
cannot stress enough that fireworks should not be used this year.
Any wildfire thats ignited has the potential for rapid spread.

&&

.SHORT TERM...
(This evening through Tuesday)
Issued at 131 PM PDT Mon Jul 1 2024

Temperatures on track today, running a couple of degrees warmer
than yesterday as of this afternoon. A sign of things to come if
you look at higher elevations though...these locations are
running between 8-15 degrees warmer than 24 hours ago. This sharp
increase in temps will extended to lower elevations by tomorrow as
what is left of the marine layer becomes further compressed by
the building high pressure aloft. Not much change in the short
term forecast as far as temperatures go. The City of San Francisco
was added to the Heat Advisory for Tuesday and Wednesday given a
slight nudge upwards in forecast temps. This resulted in moderate
HeatRisk for portions of the City, mainly the south and eastern
sides where the 90th percentile forecast is around 90 degrees. The
current official forecast is still in the low-to-mid 80s, but
there is a real possibility of seeing temps briefly spike to
around 90 in these areas if the weak offshore winds are more
productive than expected during the mid-to-late morning hours. The
western side of the City and other locations along the immediate
coast will still be on the warmer side, but will still hold on to
a bit of marine influence given that there is no synoptic driver
of persistent offshore winds with this pattern. Not to say that
some offshore winds won`t exist, but any gusty offshore winds that
do occur will be relatively short-lived and localized. Higher
elevations of the East Bay and North Bay will see increased fire
danger due to the winds Tuesday afternoon, particularly over
inland Napa/Sonoma and far eastern Contra Costa/Alameda counties.
Elsewhere and through the rest of the week, winds don`t seem to be
as big of an issue. However, fire starts will still be extremely
likely as fuels are VERY dry combined with low RH. More in the
FIRE WEATHER section below.

&&

.LONG TERM...
(Wednesday through next Sunday)
Issued at 131 PM PDT Mon Jul 1 2024

No notable change in temperatures going into Wednesday. There is a
weak mid-level shortwave trough embedded in the NW flow across the
Pac NW and Northern Rockies that may end up bringing temps down by
a couple of degrees for low-lying areas of the North Bay due to
"slightly" more marine influence to start the day. However, the
overall risk due to heat remains as temps will still be north of
100 degrees. Some of this "cool down" will spread across the rest
of the low-lying areas by Thursday taking another couple of
degrees off the highs. There is higher confidence now that we will
see temperatures peak again by the end of the week into Saturday,
thus, the Excessive Heat Warning and Heat Advisory were both
extended to Saturday night. Ensemble guidance also exhibits better
confidence that we will see a secondary peak late in the week,
advertising 850 mb temperatures around 31 C by late Saturday,
which would tie the all-time July record for 850 mb temps per the
OAK sounding. A further hint that this is a significant, multi-day
heat wave that should be taken seriously. Looking further towards
the end of the weekend, cluster analysis still exhibits some
uncertainty but is gradually coming to a better agreement in the
ridge remaining in place well into next week. For now, will keep
the expiration of heat highlights as is for Saturday night, but we
will need to continue to monitor for the possibility of extending
the advisories and warnings further.

*While we have all seen temperatures like this before, this event
 may end up approaching the upper end of what we`ve seen
 historically, in terms of longevity. While not necessarily in
 the realm of "unprecedented", this certainly fits the bill as a
 significant heat wave, especially for inland areas. Please take
 the proper precautions, as impacts will only worsen day-by-day. A
 bit on heat safety below.

HEAT SAFETY AND IMPACTS:

By now youre well aware that it is going to be extremely hot this
week with well-above normal temperatures; now lets talk about the
impacts of excessive heat and actions we can take to minimize those
impacts: With extreme heat, and especially prolonged heat events, it
is a marathon, and not a sprint. Our bodies, infrastructure, pets,
and livestock will be under duress from heat over the span of days
as opposed to just a day or two. Given that there is little
overnight relief expected throughout this event, this is where it
really becomes a marathon, and precautionary measures are
necessitated in order to prevent adverse results such as heat
exhaustion and stroke. This is not just for individuals sensitive to
heat, but rather, the entire population. Heat for this duration and
at these temperatures can be dangerous for everyone. Do your body a
favor and if you can, suspend outdoors activities between the hours
of 10am and 7pm on days where Heat Advisories or Excessive Heat
Warnings are in effect. Remain in air conditioning if you have that
available to you in your residence, or seek out air conditioned
environments such as stores, movie theaters, restaurants, libraries,
and cooling shelters.

If you cannot access air conditioned environments, must be outside,
work outdoors, or otherwise, there are other precautionary measures
you can take to keep yourself and your loved ones safe (including
pets!) during excessive heat. Take frequent breaks in the shade and
ensure that you are drinking plenty of cool water, or other
hydrating beverages such as sports drinks with electrolytes. Avoid
DEHYDRATING drinks such as alcohol or caffeinated beverages. That
aside, visiting your city public pool or a lake, river, or ocean can
also help keep you cool, but dont forget the life jacket! If
planning on swimming, stick to where there is a lifeguard, and know
the ocean or river conditions before you get in. Although outside of
our area, its worth repeating: rivers can run fast and cold with
snowmelt in the Sierra Nevada mountains, and cold water shock can
set in quickly, which can lead to loss of muscle control, and
ultimately, drowning. Cold water shock can also set in for ocean-
goers. Have fun at the water, but be smart, be safe, and Know Before
You Go!

Finally, if you do not have air conditioning or cannot access it,
and also cannot access a body of water to stay cool: consider taking
cold showers or baths, turn on those sprinklers or garden hose and
have a fun time in your own makeshift water park, or lay a damp,
cool towel across your head or body. Even just dipping your hands
and feet in cool water can help to abate feelings of excessive heat.
For pets and livestock, make sure they have access to shade
structures or areas, and have clean water freely available to them
at all times. They do not have the same resources or ability to
notify of feeling heat-stressed as we do, so check in on them! If
theyre permanently outdoors, consider giving them a quick rinse-
down with the hose or set up misters, as the evaporation will help
to keep them cool as well.

&&

.AVIATION...
(00Z TAFS)
Issued at 444 PM PDT Mon Jul 1 2024

VFR through the TAF period everywhere except MRY and SNS. Marine
layer is expected to stay fairly compressed with stratus staying
confined along the coast. In general, moderate west to northwest
winds persist into the evening before weakening overnight. Winds
become light and more variable overnight with weak, offshore flow
likely during the early morning before moderate onshore flow
returns.

Vicinity of SFO...VFR through the TAF period. Gusty conditions
persist into the late evening before weaker winds return overnight.
Light, offshore flow is likely to return overnight - main change
from previous TAF issuance was pushed back the arrival time by a few
hours. Moderate, gusty onshore flow returns by the late morning/early
afternoon and persists through the end of the TAF period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR becoming IFR to LIFR overnight.
Moderate to high confidence that stratus will return overnight for
MRY and SNS. The marine layer will remain fairly compressed
overnight which should keep ceilings on the IFR/LIFR border.
Guidance continues to indicate LIFR CIGs are more likely with
decreases in visibility possible. Moderate onshore flow persists
into the evening with lighter, more variable flow returning
overnight. Winds are expected to pick up and become more moderate

&&

.MARINE...
(Tonight through next Saturday)
Issued at 444 PM PDT Mon Jul 1 2024

  Fresh to strong north to northwest winds continue over the outer
waters through the midweek. Gale force gusts will persist through
the night tonight for the northern outer waters. Winds will
gradually weaken Wednesday and become moderate to fresh.
Significant wave heights generally build to 10-12 feet through
mid-week before abating by the late week. Portions of the northern
outer waters may see peak wave heights between 12-16 feet through
mid- week.

&&

.FIRE WEATHER...
Issued at 330 PM PDT Mon Jul 1 2024

A Red Flag Warning will be in effect starting at 11pm tonight for
some elevated locations in the North Bay Hills, East Bay Hills,
Marin and Sonoma Coastal Ranges through late tomorrow evening  with
the North Bay Hills RFW continuing until 5pm Wednesday. RH  values
are generally in the teens with gusty north/northeast offshore flow.
As the hot and dry pattern persists, fuels continue to dry. ERCs are
drying in to the 70-90 percentile range across our region.
Combine that with the expected surge of campers over the long
holiday weekend and obvious risks of fireworks, putting our area
in a combustible situation through next weekend. Fireworks should
not be used this year, and campers should be very careful with
anything dragging from trailers and securing campfires.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 11 PM PDT Wednesday for CAZ006-506-
     508.

     Heat Advisory from 11 AM Tuesday to 7 PM PDT Wednesday for
     CAZ006.

     Red Flag Warning until 11 PM PDT Tuesday for CAZ502-503-512-515.

     Excessive Heat Warning from 11 AM Tuesday to 8 PM PDT Saturday
     for CAZ502>504-506-510-512>518.

     Red Flag Warning until 5 PM PDT Wednesday for CAZ504.

     Heat Advisory from 11 AM Tuesday to 8 PM PDT Saturday for CAZ508-
     528-529.

PZ...Small Craft Advisory until 3 AM PDT Tuesday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory until 9 PM PDT this evening for Pt Pinos to
     Pt Piedras Blancas 0-10 nm.

     Gale Warning until 3 AM PDT Wednesday for Pt Arena to Pt Reyes
     10-60 NM.

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Kennedy
MARINE...AC

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