-- Discussion containing changed information from previous version are highlighted. --
757
FXUS66 KMTR 221038
AFDMTR

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

...New SYNOPSIS, SHORT TERM, LONG TERM...

.SYNOPSIS...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.SHORT TERM...
-- Changed Discussion --
(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.
-- End Changed Discussion --

&&

.LONG TERM...
-- Changed Discussion --
(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.
-- End Changed Discussion --

&&

.AVIATION...
(06Z TAFS)
Issued at 1111 PM PDT Sat Sep 21 2024

The marine layer depth currently varies from 900 feet to 1700 feet
per Bodega Bay, Fort Ord and Point Sur profilers. Coastal stratus
and fog /LIFR-IFR/ are redeveloping and will move inland tonight
and Sunday morning. Northerly and southerly pressure gradients
(and corresponding wind directions) juxtaposed over the coastal
waters within a stationary surface trough have eased since earlier
in the day; gradients were under-forecast by the meso-scale
models and with plenty of stratus/fog to our southeast along the CA
coast the SMX-SFO pressure gradient may continue Sunday. Currently
the 2.7 mb SFO-SAC pressure gradient (onshore wind) is the
predominating gradient across the forecast area. Precipitable water
on the Saturday evening Oakland upper air sounding was a little
above mid September normal, however there still should be decent
radiative cooling tonight to daybreak Sunday helping with stratus
and fog development (favorable due to lengthening night time hours).

Stratus and fog /VLIFR-IFR/ mixes out back to the coastline and
bays late Sunday morning and afternoon. Elsewhere MVFR-VFR
conditions Sunday.

Vicinity of SFO...VFR except IFR ceiling is forecast 09z 18z Sunday.
Onshore wind 5 to 15 knots.

SFO Bridge Approach...Similar to SFO.

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

&&

.MARINE...
(Tonight through next Friday)
Issued at 844 PM PDT Sat Sep 21 2024

The pressure gradient between subtropical high pressure over the
Eastern Pacific Ocean and low pressure over the West Coast will
support strong northwesterly breezes and rough seas in the outer
waters through Monday. Northwesterly breezes decrease and seas
abate beginning Tuesday. Seas rebuild to become rough in the outer
waters towards the end of the forecast period.

&&

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

&&

$$

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

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