076
FXUS66 KMTR 201134
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
434 AM PDT Sat Jul 20 2024

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 210 AM PDT Sat Jul 20 2024

A bit cooler this weekend as a weak system moves through. Warm up
still slated for early next week with moderate to major HeatRisk.
Potential for a more substantial cool down towards the end of next
week.

&&

.SHORT TERM...
(Today and tonight)
Issued at 210 AM PDT Sat Jul 20 2024

Still warm today, but temps are on their way down for the weekend.
Many locations should shave off 3-5 degrees compared to yesterday.
The Heat Advisory is no longer in effect for the weekend, but
temps far inland are still rather warm, so those especially
sensitive to heat should still exercise caution. The real story
for today comes later this evening when a transient shortwave
trough skirts through our area, causing a deepening of the marine
layer, cooler overnight temps tonight, and another few degrees
shaved off the afternoon highs tomorrow. In addition to cooler
temps, the trough is expected to bring some wind to the area.
Particularly along coastal and gap areas. The timing of this looks
to be late afternoon to early evening, which is ideal because peak
heating will have passed and humidity will be on the rise.
Therefore, fire weather concerns for today are primarily fuel
driven where we are seeing near record energy release component
among 10- and 100-hour fuels in the North Bay.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 210 AM PDT Sat Jul 20 2024

Sunday looks to be rather pleasant as temps drop a little bit
further. If you live in inland areas, this will be your chance to
spend some time outside before the next heat event. Once the
trough completely moves out by Sunday night, 500 mb height rises
continue as a ridge starts to build back in. Currently targeting
Monday through Thursday as the period of interest in which we will
see elevated HeatRisk. Particularly Tuesday and Wednesday where
areas of the South Bay and inland East Bay will see more on the
side of major HeatRisk. In terms of temps, it`s looking on par
with what we just went through. 100-105 inland, 85-95 along the
Bay, 65-75 along the coast. The marine layer looks to remain
intact as onshore flow prevails, so the thinking is that the coast
will once again be mostly shielded. We are assessing the need for
heat hazards that will likely be posted for Monday-Thursday, so
stay tuned for the latest information. On a lighter note,
temperatures start to cool off from Thursday into next weekend
with the potential for BELOW NORMAL afternoon highs by next
Saturday. There is still some uncertainty, but ensemble cluster
analysis seems to advertise this pattern relatively well, which
would result in at least some degree of cooling.

&&

.AVIATION...
(12Z TAFS)
Issued at 434 AM PDT Sat Jul 20 2024

Coastal stratus and fog /LIFR-IFR/ are developing this morning, inland
it`s VFR. The ACV-SFO pressure gradient is 7.3 mb and predominates while
the SFO-SAC pressure gradient is 2.6 mb. Onshore breezes to gusty winds
will develop today ushering cooler air inland, the cooler air also helping
to deepen the marine layer today and tonight.

Vicinity of SFO... VFR today with an increasingly gusty west wind,
afternoon and evening wind gusts to 32 knots possibly a little higher
since the NAM is forecasting 5 mb SFO-SAC pressure gradient later today
and tonight. HREF output shows IFR ceiling tonight and Sunday morning.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals...LIFR-IFR in stratus, fog and possibly patchy
morning drizzle. Conditions only gradually improving to MVFR-VFR by
late morning and afternoon, the stratus may be slow to mix out along
the immediate Monterey Bay shoreline per recent HREF output. LIFR-IFR
in stratus and fog tonight and Sunday morning.

&&

.MARINE...
(Today through Thursday)
Issued at 418 AM PDT Sat Jul 20 2024

Gusty northwest winds continuing over the coastal waters through
the weekend, with gale force gusts mainly across the northern
waters. In the unprotected waters, short period seas will
deteriorate to very rough by Sunday. Gusty winds will persist into
the work week over the outer waters.

&&

.FIRE WEATHER...
Issued at 417 PM PDT Fri Jul 19 2024

...Near critical fire weather conditions continue through
Saturday due to hot and dry conditions inland...

Dry and warm conditions continue inland with very dry fine fuels
contributing to an increased risk of fire starts. This results in
near critical fire weather conditions through Saturday across the
interior regions of the North Bay, East Bay, South Bay, and
Monterey and San Benito counties. Onshore winds will develop each
afternoon and evening, with peak gusts in the gaps and passes up
to 30 to 40 miles per hour. The strongest gusts appear to develop
for the evening hours on Saturday, but as relative humidities are
expected to be recovering from daytime minimums during the period
of peak wind gusts, the alignment between dry air and high winds
is not there for acute fire weather concerns.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 2 AM PDT Tuesday for CAZ006-506-508.

PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this
     evening for SF Bay N of Bay Bridge.

     Small Craft Advisory until 9 AM PDT this morning for Pigeon Pt
     to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena
     to Pt Reyes 10-60 NM.

     Gale Warning from 9 AM this morning to 3 AM PDT Sunday for
     Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory until 9 AM PDT Sunday for Pt Reyes to
     Pigeon Pt 0-10 nm.

     Small Craft Advisory until 3 AM PDT Sunday for Pigeon Pt to Pt
     Pinos 0-10 nm.

     Small Craft Advisory until 3 PM PDT this afternoon for Pt Pinos
     to Pt Piedras Blancas 0-10 nm.

     Gale Warning from 3 PM this afternoon to 3 AM PDT Sunday for Pt
     Pinos to Pt Piedras Blancas 0-10 nm.

     Gale Warning from 9 AM this morning to 9 PM PDT Sunday for Pt
     Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Canepa
MARINE...Canepa

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea