671
FXUS66 KMTR 240639
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1139 PM PDT Mon Sep 23 2024

...New AVIATION...

.SYNOPSIS...
Issued at 110 PM PDT Mon Sep 23 2024

Heat Advisory in effect for the interior East Bay, South Bay, and
Santa Cruz Mountains as hot temperatures peak today. Slight cooling
tomorrow with temperatures returning to near the seasonal average on
Wednesday, slightly warming by Friday.

&&

.UPDATE...
Issued at 909 PM PDT Mon Sep 23 2024

The marine layer is struggling to exist tonight, as such low-level
cloud cover is making an exit down the central coast. This will
lead to a fairly clear night with only some passing high-level
clouds. Expect some warm temperatures in the higher elevations
tonight, with a focus on the East Bay, leading to another hot day
for Tuesday. Because of the lack of relief from the heat, the East
Bay will continue to be under a Heat Advisory through tomorrow
evening with a cooler night to follow.

&&

.SHORT TERM...
(This evening through Tuesday)
Issued at 110 PM PDT Mon Sep 23 2024

Today`s warm to hot weather comes courtesy of a delicate dance in
the upper levels of the atmosphere, with a ridge sliding into the
Pacific Northwest creating warm conditions up and down the West
Coast, enhanced by a subtle low pressure system retrograding
westward off Point Conception, both features combining to create
easterly flow in the upper levels, as visible earlier this morning
with the cirrus clouds streaming into the state from Nevada.

High temperatures today rise into the mid 90s to near 100 in the
inland valleys, into the mid 80s to lower 90s along the Bayshore,
and in the mid 60s to the lower 70s along the Pacific coast. Low
temperatures tonight are generally in the upper 50s to the mid 60s
in the valleys, with some cooler temperatures at the immediate coast
where the remnants of the marine layer will lie, and up to the low
to mid 70s in the higher elevations. Some cooling is expected in the
coastal regions tomorrow, with high temperatures in places like
downtown San Francisco, the Santa Cruz county coast, and the Salinas
area dropping around 5 degrees. Across the inland areas, little
cooling is expected.

A Heat Advisory is now in effect for the interior East bay, the
South Bay, and the Santa Cruz Mountains today, due to the widespread
risk for heat related illnesses for sensitive populations (children,
the elderly, pregnant women, those with certain medical conditions),
and the possibility for heat-related impacts for everyone without
adequate hydration and/or cooling. In the South Bay and the Santa
Cruz Mountains, the Heat Advisory will expire at 8 PM today, while
the Advisory continues through Tuesday night in the interior East
Bay as lingering heat sustains the risk for heat-related illnesses.
Here`s a reminder about heat safety:

* Stay hydrated and drink plenty of fluids.
* Wear lightweight, light-colored clothing.
* Reduce time spent outdoors or stay in the shade.
* Never leave people or pets unattended in vehicles.
* Use sunscreen if going to the coast or the pool.

Winds will generally be lightly onshore in the afternoon and
evening, and calm to nearly calm overnight and into the morning.
Although some weak onshore flow is possible at the higher elevations
tonight, low wind speeds and some overnight recovery keep the fire
weather concerns low.

&&

.LONG TERM...
(Tuesday night through next Sunday)
Issued at 110 PM PDT Mon Sep 23 2024

The upper level ridge moves off to the east late Tuesday into
Wednesday, allowing the weak upper level low to merge into a
stronger upper level trough that sets up into the Eastern Pacific.
Temperatures across the region will cool rather dramatically, close
to or slightly below seasonal averages for this time of year. Later
on in the week, a zonal pattern towards our north and a series of
weak upper level troughs towards our south and southwest will keep
our region somewhat warm heading into the upcoming weekend, although
not as hot as the temperatures seen today. CPC outlooks keep a lean
towards temperatures above, and precipitations below, seasonal
averages through the first week of October.

&&

.AVIATION...
(06Z TAFS)
Issued at 1139 PM PDT Mon Sep 23 2024

The marine layer remains compressed and varied in depth from 400
to 600 feet along the north Central Coast to sea level along the
San Mateo county coastline northward to the coastal North Bay. A
coastally trapped southerly wind reversal recently developed with
the SMX-SFO pressure gradient varied between 1 mb and 2 mb. Satellite
imagery shows coastal stratus and fog /VLIFR-IFR/ advancing northward
and advancing into the northern Salinas Valley. In general forecast
models are under-forecasting the SMX-SFO gradient at the present time
and indicate the SMX-SFO strengthening Tuesday. A coupling to the mid-
upper level low to our southwest may help speed up the southerly wind
reversal pattern overnight through Tuesday.

Vicinity of SFO...VFR. Light and variable wind becoming northwest
10 to 14 knots Tuesday afternoon and evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Coastal stratus and fog /VLIFR-IFR/ are
advancing into the northern Salinas Valley while it`s VFR in the
vicinity of KMRY. A coastally trapped southerly wind reversal is
developing, however the light northwest wind (transporting stratus
and fog) to KSNS may be briefly offset by a light southeast wind
overnight. In general since meso-scale models are currently under-
forecasting the SMX-SFO (and SNS-SJC gradient) and forecast a
strengthening in that respect Tuesday, expect a general increase
in coverage of stratus and fog /VLIFR-IFR/ moving inland overnight
and Tuesday morning. Diurnal mixing Tuesday will help lift conditions
to MVFR-VFR with an early return of stratus ceilings first to KSNS
then KMRY, typically the timing for southerly wind reversals.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 909 PM PDT Mon Sep 23 2024

Gentle to moderate northwesterly breezes will continue through
Wednesday. Northwesterly breezes increase and seas rebuild to
become rough in the outer waters by Thursday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 8 PM PDT Tuesday for CAZ510-515.

PZ...None.
&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Canepa
MARINE...Sarment

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