023
FXUS66 KMTR 030347
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
847 PM PDT Tue Jul 2 2024

...New SYNOPSIS, UPDATE, MARINE...

.SYNOPSIS...
Issued at 841 PM PDT Tue Jul 2 2024

Extreme heat is expected to continue across the interior
throughout the week and potentially into next week. Meanwhile,
coastal areas are expected to remain cooler thanks to a shallow
marine layer and associated onshore flow. Increased fire danger
this week as well with temperatures well above normal and dry
conditions through out the forecast period.

&&

.UPDATE...
Issued at 841 PM PDT Tue Jul 2 2024

Inland areas were HOT this afternoon with temperatures exceeding 105
degrees across manly inland areas breaking and/or tying records.
However, cooler conditions prevailed near the immediate coast thanks
to the marine layer (around 500 feet in depth) and onshore flow with
maximum temperatures in the 60`s and 70`s. Tonight, temperatures
will not cool much but still lower into the upper 50`s to lower 70`s
in the valleys (slightly cooler along the immediate coast). However,
in the hills and higher elevations they look to remain in the mid
60`s to low 80`s providing minimal overnight relief from today`s
heat.

LOCATION                    HIGH          PREVIOUS RECORD
---------------------------------------------------------------
SAN JOSE                    102   (TIED)  102 IN 1970
SAN RAFAEL                  103           101 IN 1991
KENTFIELD                   103           101 IN 1991
SANTA ROSA                  105           103 IN 1970
OAKLAND                     90            89  IN 2001

These data are preliminary and have not undergone final quality
control by the National Centers for Environmental Information.
Therefore, these data are subject to revision. Final and certified
climate data can be accessed at www.ncei.noaa.gov.

&&

.SHORT TERM...
(This evening through Wednesday)
Issued at 158 PM PDT Tue Jul 2 2024

Current temperatures are running about 10-20 degrees warmer than
24 hours ago as the high pressure builds in. Main changes for
today have been extending and adding to our current hazards. I
will list out the changes here and talk more about them in the
next section since they carry over into the "long term". The Heat
Advisory for San Francisco has been extended to include Thursday.
The Heat Advisory and Excessive Heat Warning for all other
locations originally included have been extended to NEXT Tuesday
night. The Red Flag Warnings in the North Bay, Santa Cruz Mtns,
and East Bay Hills have been extended to Friday morning. Finally,
a Fire Weather Watch was added for interior portions of Monterey
and San Bentio Counties, Santa Lucia, and the Southern Salinas
Valley for Friday through Sunday. In terms of the forecast from
today into Wednesday, there will be no significant change. Some
locations may see a degree or two taken off their highs while
other will see a degree or two added. Wednesday afternoon, there
is a very weak mid-level perturbation that will bring some degree
of marine influence to coastal areas and locations around the Bay.
While not a significant or even noticeable cool off by any means
for most, this may help to limit high temps a bit for San
Francisco Wednesday evening going into Thursday. On to the long
term to discuss what we expect to happen going forward.

&&

.LONG TERM...
(Thursday and beyond)
Issued at 158 PM PDT Tue Jul 2 2024

The heat isn`t going anywhere any time soon. Long range guidance
and cluster analysis strongly suggest this pattern is here to
stay through at least the beginning of next week. Some areas may
see a couple of degrees shaved off before the weekend, but it will
stay hot. A secondary peak is expected by the weekend into early
next week. While it may seem manageable based on looking at a
single day of these temps, the length of this event will present
an extremely dangerous and potentially historic event. Jogging
back in "recent" memory, to find the next most significant heat
event in terms of overall scale and longevity, you have to look
back to 2006. Sure, some locations have seen higher temps in more
recent memory, but this many days in a row may actually be
challenging some records based on the current forecast. How long
will this actually last? Good question. Taking a look at the
ensemble guidance for 850 mb temps...the forecast mean for OAK
remains above the 90th percentile and near the maximum moving
average through NEXT Friday, July 12. This is especially alarming
when compared with a look at how models are handling the overall
pattern. In the aforementioned cluster analysis, only 2% of total
members support a flattening of the ridge by mid-to-late next
week. This strongly suggests that there is high confidence in this
pattern and associated heat wave lasting through the forecast
period. This aided in the decision to extended the Excessive Heat
Warning out for 8 consecutive days, an unprecedented action from
our office.

It cannot be stressed enough that this is an exceptionally
dangerous and lethal situation. It may not seem so if you live
near the coast, but an event of this scale, magnitude, and
longevity will likely rival anything we`ve seen in the last 18
years for inland areas. Several days of temperatures well above
normal and little relief overnight will lead to compounding
effects among people and infrastructure, with the possibility of
numerous heat related fatalities and rolling black outs. Heat is
the number one weather related killer in the United States. By
this weekend, it is VERY LIKELY that we add to that statistic if
preparations are not taken seriously.

&&

.AVIATION...
(00Z TAFS)
Issued at 427 PM PDT Tue Jul 2 2024

VFR through the TAF period except for Monterey Bay. High pressure
will continue to provide clear skies, though haze may begin to
appear in the late afternoon and evenings as pollution is trapped
near the ground. Haze may reduce visibilities slightly below 10
miles. Aside from this, winds decrease to become light and
variable tonight, with a few locations seeing light offshore flow.

Vicinity of SFO...VFR through the TAF period. Light easterly flow is
likely to develop in the morning Wednesday, but will turn to become
more NW and breezy into the late morning and early afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR persists through the late night
tonight, though stratus is expected to begin to trickle in bringing
intermittent LIFR CIGs. With the severe compression of the marine
layer, and light offshore flow expected overnight, there remains
some question as to whether CIGs will actually form over KMRY and
KSNS. The compression and light offshore flow could be just enough
to erode any stratus that begins to form. Models do indicate
stratus forming over terminals in the late night tonight and early
morning Wednesday, but given the aforementioned, confidence on
CIG formation is only moderate. However, should CIGs form,
confidence is high that they will be LIFR given the severe
compression from high pressure. That all aside, VFR returns
towards sunrise and lasts through the remainder of the TAF period.

&&

.MARINE...
Issued at 841 PM PDT Tue Jul 2 2024

Fresh northerly winds continue over the outer coastal waters
today, with gale force gusts expected over the northern outer
waters through early Wednesday morning. As high pressure
strengthens and moves eastward, winds begin to diminish late
tomorrow night. Winds from late tomorrow night through the
weekend are expected to be predominantly gentle to moderate.
Portions of the northern outer waters may see peak wave heights
between 12-16 feet through the late afternoon of Wednesday.

&&

.FIRE WEATHER...
Issued at 354 PM PDT Tue Jul 2 2024

Red Flag Warnings currently in effect for high elevations of the
North Bay, East Bay Hills, and the Santa Cruz Mtns have been
extended to 5AM Friday. This decision was made due to a
combination of continued low RH in the teens, very dry fuels, and
the 4th of July holiday. Fuels are quickly curing and will see no
relief through this weekend. In fact, 10 and 100 hour fuels are
near historic levels in the North Bay in regard to the energy
release component going into the weekend. The same fuels in the
Diablo Range and Santa Cruz Mtns aren`t far behind. Further south,
things start to dry out more this weekend. A Fire Weather Watch is
in effect for the Santa Lucia Range, Interior Monterey and San
Benito county, and the Southern Salinas Valley from Friday morning
to Sunday night.

Behringer

&&

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

     Heat Advisory until 7 PM PDT Thursday for CAZ006.

     Excessive Heat Warning until 11 PM PDT Tuesday for CAZ502>504-
     506-510-512>518.

     Red Flag Warning until 5 AM PDT Friday for CAZ502>504-512-515.

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

     Fire Weather Watch from Friday morning through Sunday evening
     for CAZ516>518.

PZ...Small Craft Advisory until 3 AM PDT Wednesday for Pt Arena to Pt
     Reyes 0-10 nm.

     Gale Warning until 9 AM PDT Wednesday for Pt Arena to Pt Reyes
     10-60 NM.

     Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt
     to Pt Pinos 10-60 NM.

&&

$$

UPDATE/SYNOPSIS...RGass
SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...AC
MARINE...AC
FIRE WEATHER...Behringer

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