486
FXUS66 KMTR 270539
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1039 PM PDT Thu Sep 26 2024

...New AVIATION, MARINE...

.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...
(06Z TAFS)
Issued at 1039 PM PDT Thu Sep 26 2024

At this hour, satellite shows stratus pushing inland through the
Salinas valley and around Monterey Bay. The marine layer remains
compressed from high pressure, and visibilities at several airports
in the Monterey regions are reporting less than 1 SM. Throughout the
night, expecting Monterey Bay terminals to continue to see IFR/LIFR
conditions as a result of low stratus and fog. Elsewhere is likely
to remain VFR as stratus is not thought to advect far inland
tonight, remaining largely at the coastline. North Bay terminals may
see slight visby reductions as mist/light fog develops thanks to
radiational cooling and a moisture influx, though confidence on any
fog development for the North Bay is currently low-moderate.
Otherwise, winds light overnight for most terminals and variable.
W/NW breezy winds return in the afternoon Friday for the majority
of terminals alongside VFR conditions.

Vicinity of SFO...VFR through the TAF period. Stratus is not
expected to make any meaningful push into the SF Bay overnight.
Breezy NW winds return in the afternoon, but ease to become light
into the late night Friday.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR CIGs and visbys persist through at
least sunrise Friday. The well compressed marine layer is keeping
stratus trapped close to the ground, allowing for significant
reductions in visbys. It is not until closer to the 16-17Z window
Friday that stratus and fog is expected to begin to mix out and
erode. Beyond this timeframe, a return of VFR conditions is
expected, lasting through the evening Friday.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 1039 PM PDT Thu Sep 26 2024

A series of low pressure systems will begin to move into the
Pacific Northwest this week and support continued moderate to
fresh northwesterly breezes over the outer waters. Significant
wave heights will build over the outer waters to 8 to 10 feet by
this weekend. Over the northern outer waters significant waves
heights between 8 to 12 feet, rough seas, and strong gusts will
continue through the end of the forecast period.

&&

.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 3 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...AC
MARINE...Sarment

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