330
FXUS66 KMTR 050933
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
133 AM PST Wed Feb 5 2025

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

.SYNOPSIS...
Issued at 1209 AM PST Wed Feb 5 2025

The cold front has passed through and much more benign weather is
in store today. A weaker system will bring another round of rain
Thursday before a dry and cold weekend.

&&

.SHORT TERM...
(Today and tonight)
Issued at 1209 AM PST Wed Feb 5 2025

Colder and drier air has settled in following yesterday`s cold
front. The satellite shows some cumulus clouds over the water, but
any showers are expected to be brief. The drier air mass has
precipitable water values of 50-75% of normal. Overall today will
be a reprieve between 2 systems. The colder air mass will be
noticeable, however. The current temperatures are roughly 10
degrees colder than 24 hours ago and a frost advisory is in effect
for the North Bay Valleys this morning. More frost advisories may
be needed tonight, but the increasing cloud cover ahead of
Thursday`s system will suppress radiational cooling and will
likely keep the region a degree or two warmer than this morning.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 1209 AM PST Wed Feb 5 2025

By Thursday morning another plume of moisture will reach the
coast as a surface low pressure system develops offshore. There is
an outside chance for thunderstorms off the coast Thursday
afternoon. Compared to the atmospheric river on Tuesday, this
system will be much weaker in terms of both wind and rain.
Rainfall amounts are generally expected to be 0.25-1.25". The wind
will still be noticeable, with SW winds 10-20 mph and gusts up to
35 mph Thursday evening. This system will also bring a
reinforcing shot of colder air as it departs. The 1000-500 mb
thickness will fall to around 5,400 m by Friday. In fact, the snow
levels will drop to around 3,000 ft and there`s a chance some of
the higher mountains will get a few flakes. Otherwise Friday will
be a transition day as the skies gradually clear and the drier
ridging pattern stabilizes.

By the weekend, the only real hazard becomes cold morning
temperatures. Saturday morning will start roughly 10 degrees
colder than Friday morning. Many inland areas will drop into the
low 30s, and widespread frost advisories are expected. Afternoon
highs will only climb into the mid to upper 50s, so it will feel
chilly all day, although there will be ample sunshine. The ridging
pattern stabilizes through mid week, and the weather will be
pretty consistent. The next round of rain looks to arrive around
Wednesday.

&&

.AVIATION...
(06Z TAFS)
Issued at 949 PM PST Tue Feb 4 2025

CIGs continue to lift in the post frontal environment leading to
widespread VFR in the late night for all but the North Bay which will
see some pockets of fog and mist. Additional showers move through the
region in the late night through the morning for the SF Bay and
North Bay Terminals. Moderate winds turn light overnight and become
moderate again into Wednesday afternoon then light again that night.

Vicinity of SFO...VFR through the TAF period. Expect gusty winds to
east overnight and become light into early Wednesday. Showers pass
through the area in the early morning but exit by the late morning.
Moderate west winds arrive for Wednesday afternoon but become light
and variable that night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...CIGs lift into the late night with moderate
winds weakening into Wednesday morning. Moderate west winds arrive
Wednesday afternoon before weakening that evening.

&&

.MARINE...
(Tonight through next Monday)
Issued at 949 PM PST Tue Feb 4 2025

Showers and storms are exiting as winds begin to ease. Lingering
gusty winds will cause hazardous conditions for small craft into
early Wednesday for much of the waters, but will subside through
the rest of the morning.  Another storm system will impact the
coastal waters Thursday into Friday with increasing winds and
rain.

&&

.HYDROLOGY...
Issued at 1209 AM PST Wed Feb 5 2025

While the rain has ended, river flooding continues. Fortunately it
looks like the Napa River will not reach minor flood stage, a big
change after the earlier forecast suggesting it could reach major
flood stage. It`s currently hovering around 23.5 ft. The Russian
River at Guerneville forecast has stabilized, and it looks like
it will reach moderate flood stage (35 ft) in the next few hours.
The river is expected to crest around 35.6 ft by 8 AM, and recede
out of flood stage Wednesday night. The San Lorenzo River at Big
Trees rose quickly last night, but didn`t quite reach action stage
and receded nearly as fast. For the areal flood warning in
central Sonoma County, moderate flooding is ongoing at 3 gauges
(Green Valley Creek at Martinelli Road, Colgan Creek near
Sebastopol, and Mark West Creek near Mirabel Heights). 2 of these
rivers are receding, but Mark West Creek near Mirabel Heights will
likely crest above major flood stage (65 ft) in the next few
hours before receding. Residual flooding will persist through
Thursday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory until 9 AM PST this morning for CAZ506.

PZ...Small Craft Advisory until 3 AM PST early this morning for Mry
     Bay-Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-
     60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-
     60 NM-Pt Reyes to Pigeon Pt 0-10 nm-SF Bay N of Bay Bridge.

     Small Craft Advisory until 9 PM PST this evening for Pt Pinos to
     Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Murdock
MARINE...Murdock

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