580
FXUS66 KMTR 130934
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
134 AM PST Mon Jan 13 2025

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

.SYNOPSIS...
Issued at 1215 AM PST Mon Jan 13 2025

Dry conditions continue this week with mostly clear skies, some
gusty offshore winds, and chilly mornings.

&&

.SHORT TERM...
(Today and tonight)
Issued at 1215 AM PST Mon Jan 13 2025

Believe it or not, the pattern is changing tonight. A short wave
trough at 500 mb is moving through the Bay Area, bringing a patch
of mid to high level clouds. Over the next 24 hours, this feature
will continue to dive south, and become cut-off roughly 500 miles
west of northern Baja. At the same time, a ridge from the Eastern
Pacific subtropical high will slide over the top, towards the
Pacific Northwest. This will create a situation with high pressure
directly north of low pressure, or a Rex Block.

With lighter winds, the temperatures are dropping more efficiently
tonight. The mid to high level clouds will put a damper on the
cooling, but only briefly. The Satellite loop shows we will only
be dealing with these clouds for a couple hours before the clear
skies return.

This pattern will also support another round of strong offshore
winds through Tuesday, but not quite as widespread or as strong as
the recent wind advisory. Winds will calm by mid-week as the cut-
off low gradually fills in the absences of any upper level
support.

&&

.LONG TERM...
(Tuesday through Sunday)
Issued at 1215 AM PST Mon Jan 13 2025

The new Rex Block pattern will live up to its name, keeping the
weather consistent through the week. The skies will stay mostly clear
with no chance of rain. Offshore winds will persist through mid-
week, with decreasing intensity. The 850 mb temperature will
remain between the 50th and 75th percentile for this time of
year. The clear skies and dry air mass will enhance radiational
cooling at night. Minimum temperatures will range from the mid 30s
inland to mid 40s near the coast. Maximum temperatures will be in
the low to mid 60s for most.

By Friday, the pattern will begin to break down as the low west of
Baja gets reabsorbed into a trough moving through the desert SW.
This will allow a return to the Omega Block pattern that we had
all of last week. This Omega Block - Rex Block - Omega Block
combination is bringing unusually dry weather to what is
typically the wettest time of the year. Downtown San Francisco has
only recorded 0.19" of precipitation so far in January, when the
normal for the first 2 weeks is over 2". The extended guidance and
CPC outlooks suggests there is a good chance this next omega
block keeps us dry through the following week and possibly all the
way to the end of the month.

With the fires in Los Angeles and the prolonged dry spell here,
we are starting to take a peek at fuel moisture. The energy
release components have responded quickly to this weather, and are
well above normal for this time of year. Fortunately, we entered
the month in a much better place than southern California, and
nearly all zones are still below the 60th percentile for the
annual average. The Central Coast zone is the exception, as the
ERC has recently crossed the 60th percentile and is expected to
reach the 80th over the next week. For the first time in months,
the Southern California Geographic Area Coordination Center has
placed the Central Coast Zone (coastal Monterey County) in a low
risk of significant fire potential starting Sunday and continuing
through the end of the forecast (Saturday). The rest of our area
remains in the "little to no risk" category this week.

&&

.AVIATION...
(06Z TAFS)
Issued at 924 PM PST Sun Jan 12 2025

VFR continues to prevail through the TAF period as satellite
continues to show clear skies across the terminals. Winds have
become light and variable but expect breezy conditions early Monday
morning with possible gusty conditions for most terminals. Winds
will returns to light to moderate towards late Monday afternoon.
LLWS/low level turbulence is possible for terminals in the North
Bay as a low-level jet is anticipated to pass over the North Bay
terminals tonight, especially over KSTS.

Vicinity of SFO...VFR through the TAF period. Light westerly winds
but near 12Z N/NE winds rebuild to up to 15-16 knots. Winds remain
breezy into the early afternoon before returning to light to
moderate through the remainder of the TAF period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Light winds
continue into the night especially for KMRY. KSNS is currently
seeing SE wind and will build to moderate overnight.

&&

.MARINE...
(Tonight through next Saturday)
Issued at 924 PM PST Sun Jan 12 2025

Strong winds continue across portions of the northern outer
waters with gale force gusts. Breezy to gusty winds continue for
the waters through early Monday morning, but look to ease into
the work week. Hazardous conditions for small crafts will persist
through Monday with elevated wave heights between 10 to 15 feet
expected. Significant wave heights will remain elevated through
the early work week but will subside below small craft criteria by
mid week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory from 7 AM this morning to 1 PM PST this
     afternoon for CAZ006-506-508.

     Wind Advisory until 10 AM PST Tuesday for CAZ504.

     Frost Advisory until 9 AM PST this morning for CAZ510-513>518-
     528.

PZ...Small Craft Advisory until 3 PM PST this afternoon for Pt Reyes
     to Pigeon Pt 0-10 nm-SF Bay N of Bay Bridge.

     Small Craft Advisory until 3 PM PST this afternoon for Pigeon Pt
     to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

     Gale Warning until 9 AM PST this morning for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...SO
MARINE...KR

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