505
FXUS66 KMTR 221558
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
858 AM PDT Sun Sep 22 2024

...New UPDATE, MARINE...

.SYNOPSIS...
Issued at 337 AM PDT Sun Sep 22 2024

Temperatures will continue to warm this afternoon, with highs in the
low 90s inland across the North Bay, East Bay and higher elevations
above the marine layer extending south into Monterey County and San
Benito County. The heat builds further Monday and Tuesday, with
areas of moderate HeatRisk possible for inland locations not under
the influence of the marine layer.

&&

.UPDATE...
Issued at 853 AM PDT Sun Sep 22 2024

Extensive stratus coverage has developed across the valleys this
morning, beginning to mix out along the very fringes of the
stratus deck. The 24-hour temperature trends show temperatures
across the region running near or slightly above those seen this
time yesterday. Still expecting a warming trend to continue today
and Monday, but possibly not as dramatic as the current forecast
shows. Will evaluate the trends throughout the rest of the
morning, taking a closer look at the short-term temperature
forecast with the afternoon forecast package.

DialH

&&

.SHORT TERM...
(Today and tonight)
Issued at 337 AM PDT Sun Sep 22 2024

Low level ridging below a slow developing upper level weakness in
the H50 height fields will result in warmer temperatures today and
then climb even higher tomorrow to start the work week with moderate
HeatRisk possible for inland locations away from the marine layer.
Deterministic guidance has consistently advertised the weakly forced
upper level disturbance, though the exact location and evolution
over the next couple days has been difficult to pin down. It has
likely limited the impacts of the heat somewhat over the next few
days, but highs on Monday will still be in the mid 90s to near 100
inland across the North, South and East Bay, also farther south into
Monterey County above the marine layer and San Benito County.

&&

.LONG TERM...
(Monday through Saturday)
Issued at 337 AM PDT Sun Sep 22 2024

The potential for moderate HeatRisk will extend into Tuesday under a
stagnant airmass between a developing upper low offshore to our west
and building ridge over the Intermountain West. By Wednesday, the
offshore upper low merges with a strengthening trough over the
Pacific Northwest. The upper troughing to our north will spread
cooler temperatures aloft over our region, resulting in lower
surface temperatures closer to normal for this time of year for
Wednesday and beyond, while another upper level disturbance develops
offshore of SOCAL and remains quasi-stationary into next weekend.

&&

.AVIATION...
(12Z TAFS)
Issued at 432 AM PDT Sun Sep 22 2024

Coastal stratus and fog /LIFR-IFR/ are redeveloping and moving
inland this morning. Stratus and fog /VLIFR-IFR/ will mix out
back to the coastline and bays late this morning and afternoon.
Elsewhere MVFR-VFR conditions today.

Vicinity of SFO...IFR ceiling is forecast 09z-18z today, then
VFR. IFR redeveloping tonight and Monday morning. Onshore wind 5
to 15 knots.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR-IFR in stratus and fog this
morning, conditions improving to MVFR-VFR by late morning and
early afternoon. IFR redeveloping tonight and Monday morning.
Light and variable winds this morning becoming onshore 5 to 15
knots by late morning and afternoon.

&&

.MARINE...
(Today through Friday)
Issued at 853 AM PDT Sun Sep 22 2024

High pressure over the Eastern PAcific and low pressure over
California will lead to breezy northwesterly flow over the coastal
waters through at least Monday. Winds will be strongest over outer
waters north of Point Reyes. The locally stronger winds will
result in a steeper fresh swell. Northwesterly breezes decreasing
and seas abating Tuesday. Seas rebuilding to become rough in the
outer waters towards the end of the forecast period.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 AM PDT Monday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Canepa
MARINE...MM

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