923
FXUS66 KMTR 130303
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
703 PM PST Sun Jan 12 2025

...New UPDATE...

.SYNOPSIS...
Issued at 1243 PM PST Sun Jan 12 2025

Dry and mild days followed by cold nights will persist through
next week.

&&

.UPDATE...
Issued at 650 PM PST Sun Jan 12 2025

Temperatures are trending downward as the observations shows the
24-hour change reflecting 3-7 degrees lower than yesterday. Expect
clear skies to continue tonight, allowing the opportunity for
temperatures to reach low 30s to low 40s. Therefore, the forecast
overall remains on track as we continue to have the Frost Advisory
out for overnight temperatures and the Wind Advisory for gusty
northerly to northeasterly winds. Read below for more details.


&&

.SHORT TERM...
(This evening through Monday)
Issued at 1243 PM PST Sun Jan 12 2025

Today will bring plentiful sunshine and dry conditions with
temperatures as much as 10 degrees above normal. Clear conditions
overnight will maximize radiational cooling, thus a Frost Advisory
has been issued from 1 AM Monday through 9 AM Monday for the East
Bay Hills, East Bay Valleys, Santa Clara Valley, Eastern Santa Clara
Hills, and Interior Central Coast. The coldest conditions are
expected outside of major cities due to the urban heat island
effect, i.e. temperatures of 33 to 36 degrees are not expected in
San Jose but are expected in southern portions of the Santa Clara
Valley along the US-101 corridor. Please make sure that pets and
plants have appropriate shelter.

The overall upper air pattern is in an Omega Block; however, by this
evening a shortwave trough will dig from north to south and become a
cutoff low over the Eastern Pacific Ocean forming a Rex Block. At
the surface there is a coastal trough off the West Coast and high
pressure across the West. This is a textbook offshore flow setup.
Evidence of that is a -5.7 mb SFO-WMC surface pressure gradient
which is forecast to strengthen through Monday morning as the
shortwave trough traverses the region. The surface pressure
gradient is expected to be tightest over the North Bay, thus a
Wind Advisory has been issued from 2 AM Monday through 10 AM
Tuesday for the North Bay Interior Mountains for northerly to
northeasterly winds of 25 to 35 mph with gusts up to 55 mph. The
downsloping (warming) nature of the winds will keep the North Bay
just warm enough to remain excluded from the Frost Advisory for
tonight.

A Coastal Flood Advisory is in effect from 7 AM to 1 PM Monday for
bayshore locations along the San Francisco Bay and San Pablo Bay.
Expect minor coastal flooding from King Tides, particularly in low-
lying roadways of Marin County.

&&

.LONG TERM...
(Monday night through next Saturday)
Issued at 1243 PM PST Sun Jan 12 2025

Tuesday through Saturday is more of the same: dry and mild. The Rex
Block is expected to break down Thursday which will allow for the
return of at least some onshore flow in the form of the afternoon
sea breeze. The dry air mass and lack of clouds will continue to
allow for maximal radiational cooling overnight with Frost
Advisories likely needed every night this week in at least one
zone. Want an inside scoop? CPC has the region leaning below
normal for temperatures and precipitation through January 26th.
Now would be a great time to get outdoor projects done like making
sure your gutters are cleaned out and loose tree limbs are
removed, or you can simply enjoy the beach in January.

&&

.AVIATION...
(00Z TAFS)
Issued at 312 PM PST Sun Jan 12 2025

Clear skies throughout the region. VFR will prevail through the TAF
period. N/NE winds will will remain moderate to breezy into the
evening hours before becoming light temporarily. Early Monday
morning expect breezy and gusty conditions to return for most
terminals and will linger into the early afternoon hours before
returning to moderate speeds. LLWS is possible for terminals in the
North Bay as a low-level jet passes over the terminal, especially
over KSTS.

Vicinity of SFO...VFR through the TAF period with light to variable
winds into the night. Near 12Z N/NE winds rebuild to up to 15-16
knots and expected to linger into the early afternoon before
moderate speeds return. Timing is a bit uncertain as some models
suggest winds ease near 22-23Z.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Light winds
continue into the night. SE moderate to breezy drainage winds build
near the terminals overnight, especially over KSNS.

&&

.MARINE...
(Tonight through next Friday)
Issued at 312 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 late tonight and 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 to 1 PM PST Monday for CAZ006-
     506-508.

     Wind Advisory from 2 AM Monday to 10 AM PST Tuesday for CAZ504.

     Frost Advisory from 1 AM to 9 AM PST Monday for CAZ510-513>518-
     528.

PZ...Small Craft Advisory from 3 AM to 3 PM PST Monday for Pt Reyes
     to Pigeon Pt 0-10 nm-SF Bay N of Bay Bridge.

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

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

&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...SO
MARINE...RGass

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