420
FXUS66 KMTR 240413
AFDMTR

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

...New UPDATE, MARINE...

.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...
(00Z TAFS)
Issued at 439 PM PDT Mon Sep 23 2024

Currently VFR at all terminals. High confidence in VFR through the
TAF period at all terminals except the Monterey Bay terminals of MRY
and SNS as high pressure has effectively eroded the marine layer.
Winds will become light overnight with the sea breeze on tap for
tomorrow afternoon.

Vicinity of SFO...Currently VFR with westerly flow. High confidence
in VFR through the TAF period. Winds will become light overnight,
prevailing out of the west by tomorrow afternoon when the sea breeze
kicks in.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently VFR with northerly flow at MRY
and VFR with northwesterly flow at SNS. Confidence is decreasing on
either of the terminals becoming anything but VFR due to warmer and
drier conditions, offshore flow which will further dry the low-
levels, and a non-existent marine layer. If either terminal were to
become non-VFR it would likely be LIFR in the form of fog somewhere
between 04Z and 19Z with higher confidence in the latter half of the
timeframe.

&&

.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...Sarment
MARINE...Sarment

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