453
FXUS66 KMTR 270343
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
843 PM PDT Thu Sep 26 2024

...New SYNOPSIS, UPDATE...

.SYNOPSIS...
Issued at 835 PM PDT Thu Sep 26 2024

Above normal temperatures tomorrow with slightly cooler temps
over the weekend. Another warmup for the beginning of next week
will bring more moderate HeatRisk to many inland locations on
Monday and Tuesday.

&&

.UPDATE...
Issued at 835 PM PDT Thu Sep 26 2024

No update to the forecast necessary tonight. Some low stratus is
filling into coastal communities along Monterey Bay and the
Salinas Valley tonight, along with a well defined eddy over the
waters of Monterey Bay as of 8:45 PM PDT. The marine boundary
layer has begun to compress as well per the Ft Ord profiler and
may help to produce periods of drizzle and patchy fog overnight
along the Central Coast.

&&

.SHORT TERM...
(This evening through Friday)
Issued at 1206 PM PDT Thu Sep 26 2024

Temperatures on the rise today as high pressure builds aloft and
compresses the marine layer. Current temps running around 10-15
degrees warmer than 24 hours ago for areas away from the
coastline. This trend will continue on Friday as the marine layer
compression continues. There is a slight chance of weak offshore
winds during the early morning hours Friday that would help erode
the marine layer and result in temps slightly above forecast
tomorrow afternoon. This is not a widespread offshore wind event,
but rather a subtle feature that affects the confidence of
tomorrow`s forecast high, especially along the coast where the
presence, or lack, of marine layer can result in a large
difference in temperatures over short distances. The offshore
gradient does not look like it will last too long, however. High
confidence that onshore winds will take over during the afternoon,
bringing temps back down as the marine layer returns.

&&

.LONG TERM...
(Friday night through next Wednesday)
Issued at 1206 PM PDT Thu Sep 26 2024

Still on track for a flattening of the ridge via upper level
trough moving into the PNW through this weekend. That will result
in a deepening of the marine layer and slightly cooler temps over
the weekend before the next round of warm weather. The next
impactful period of weather looks to be the Tuesday/Wednesday
timeframe with well above average temperatures. Confidence is
high in the pattern supporting high temperatures about 15-20
degrees above normal inland and 5-10 degrees above normal along
the coastline. Like the weak offshore flow Friday, a weak upper
low pressure system lingering off the southern California coast
will promote light offshore flow that will likely erode the marine
layer along the coast. This looks like it could be among the
warmest days that the immediate coastline have seen so far this
summer. It doesn`t look like anything over the top based on the
current forecast, but certainly warm for these areas. High temps
Tuesday along the immediate coast will be in the 70s to mid-80s,
and the 90s to near 100 inland. In terms of fire weather, things
will be very dry with fuels forecast to near record levels,
particularly in the North Bay. However, the winds don`t appear to
be critical at the moment, and the current forecast appears to
support decent moisture return overnight compared to a true
offshore wind event. Fire danger is certainly elevated, but not
critical at this time. Beyond the middle of the week, the pattern
begins to break down again and become a little more uncertain.

&&

.AVIATION...
(00Z TAFS)
Issued at 449 PM PDT Thu Sep 26 2024

Generally VFR tonight with the exception being MRY and SNS where a
condensed marine layer will be supportive of IFR-LIFR CIGs and
reduced visibilities. High pressure will retrograde overnight and is
increasing confidence that the marine layer will significantly
compress and prevent widespread stratus development away from the
immediate coast. Low confidence that fog will develop at STS and APC
overnight but some potential remains from 12-16Z. Winds generally
stay light and variable overnight with guidance suggesting light (<3
knots) offshore winds may develop during the early morning. West to
northwest winds generally strengthen to 8-16 knots during the
afternoon/evening.

Vicinity of SFO...VFR through the TAF period. High confidence that a
compressed marine layer will prevent CIGs from developing at SFO.
Moderate west to northwest winds continue into the evening before
weakening overnight. By the early morning, light winds will
generally be variable but may go offshore during the early morning
hours. Moderate west to northwest winds are expected to return by
the afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Moderate confidence that a compressed
marine layer will lead to IFR-LIFR CIGs overnight. Satellite shows
stratus entering the Monterey Peninsula with KOAR reporting an
overcast ceiling at 300 ft as of 3PM. Current thinking is patchy
stratus will persist for the next few hours before more widespread
stratus returns late this evening. Northwest winds will continue to
weaken through the evening and will become more variable to lightly
offshore overnight. CIGs are expected to clear by mid morning with
moderate northwest winds returning by the afternoon.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 449 PM PDT Thu Sep 26 2024

A parade of low pressure systems into the Pacific Northwest will
support moderate to fresh northwesterly breezes. Over the outer
waters, seas will be rough and gusts will be strong.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 PM PDT Saturday for Pt Arena to Pt
     Reyes 10-60 NM.

     Small Craft Advisory until 9 AM PDT Friday for Pigeon Pt to Pt
     Pinos 10-60 NM.

     Small Craft Advisory from 3 AM to 3 PM PDT Saturday for Pigeon
     Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Kennedy
MARINE...Sarment

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