772
FXUS66 KMTR 060059
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
459 PM PST Wed Feb 5 2025

...New AVIATION, MARINE...

.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...
Issued at 250 PM PST Wed Feb 5 2025
(This afternoon through Thursday)

A much needed break this afternoon as one system exits and another
approaches from the west. The sun is out for most areas, but
temperatures are on the cooler side being on the backside of the
departing storm system. Moist zonal flow aloft with a slight
ripple in the 500mb flow is helping to pop a few showers far
North Bay this afternoon.

Tonight: Frost Advisory has been issued for the North and East Bay
Valleys and Southern Salinas Valley. On the lower confidence side
given clouds ahead of the next system could prevent from colder
temperatures from being realized. However, given the recent rains
and damp conditions think marginal conditions will be a bigger
impact for the unhoused population and those without adequate
shelter. Probabilistic information also tipped the hand toward a
Frost Advisory as probs for temps less than 36 deg is 85%.
Temperatures in the Frost Advisory will be 33 to 38 degrees.
Outside of the Frost Advisory area it will still be on the cool
side with lows in the 30s to lower 40s.

Thursday: Another AR will take aim at California. Latest marine
surface analysis shows a low pressure system near 32N 145W
tracking NE. There is also a moisture plume associated with this
low extending back to the tropics. While it`s another AR it will
not have the dynamics or full moisture tap like the last one.
PWATs with the Thursday AR are closer to 1" with IVT/IWV more in
the range of weak/moderate. Precip on Thursday will come in two
waves: initially more stratiform precip as the warm sector and
warm front lift through and then a stronger push later in the
day/evening as the cold front and low pressure move through. Rain
rates look to be highest with the cold front. Additionally,
convective parameters increase into the afternoon: sfc and MU
CAPE, 0-1km and 0-6km shear, upper level jet support, and steeper
lapse rates. As such, thunderstorms have been added to the
forecast. Most likely coastal waters and North Bay. From a hydro
perspective any additional precip, stratiform or convective, will
be problematic with wet soils and full creeks/stream. Therefore,
a Flood Watch was issued for Marin and Sonoma counties Thurs AM
through Friday afternoon. Lastly, as the surface low approaches
from the west through out the day southerly flow will increase
over the region. Winds will not be as strong as Tuesday, but gusty
nonetheless. Winds will be strongest over the coastal waters,
immediate coast, mts, and S-N oriented valleys. No Wind Adv
expected at this time, but gusts 40-50 mph.

&&

.LONG TERM...
Issued at 130 PM PST Wed Feb 5 2025
(Thursday night through next Tuesday)

For the upcoming weekend, the main concern will be cold overnight
temperatures! By Saturday morning, temperatures will roughly be 10
degrees colder than Friday morning and range from the upper 20s in
wind sheltered interior valleys, with widespread low-to-mid 30s
across much of the interior. However, major urban areas of San
Francisco, Oakland, San Jose and other coastal locations will likely
drop into the mid-to-upper 30s to lower 40s. Thus, frost and freeze
products will be again likely this weekend into next week. Afternoon
highs will only warm into the mid-to-upper 50s despite the abundant
sunshine.

Confidence is increasing for seeing our next round of rain beginning
by Wednesday and continuing at times through the following weekend.
However, this remains about 7-8 days out and details remain limited
in the what, where, and when. However, the Climate Prediction
Center`s 6-10 Day Outlook indicates below average temperatures and
above average precipitation. Be sure to keep up to date with the
latest forecast information from reliable sources.

&&

.AVIATION...
(00Z TAFS)
Issued at 452 PM PST Wed Feb 5 2025


Widespread VFR lasts into early Thursday with moderate winds from
this afternoon turning light overnight. Cigs and visibilities fall
as the next rain system builds into the area. Rain arrives mid
morning for the North Bay and spreads region-wide into the late
morning. Expect southerly winds to increase as the rain builds into
the area with strong gusts expected  for most areas through Thursday
afternoon and evening.

Vicinity of SFO...VFR lasts into Thursday. Moderate west winds turn
light and variable into the night. Southeast winds build into mid
Thursday morning as showers near the terminal. These winds become
gusty in the late morning as rain rates increase. Lower clouds move
through the areas that afternoon with MVFR CIGS expected and winds
continue to increase that afternoon.



SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR last into the late morning of Thursday.
Winds become light this evening but become more moderate and
southeasterly into early Thursday. Rain  and MVFR CIGs build into
the late morning and increases into that afternoon. Strong, gusty
winds build into that afternoon and CIGs continue to lower.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 452 PM PST Wed Feb 5 2025

Winds and waves continue to ease across the waters through
Wednesday night. Strong winds build over the waters early
Thursday morning and continue into the weekend as another
atmospheric river approaches the region. This system will bring
rain back to the coastal waters Thursday and into Friday.
Moderate to strong winds will persist over the waters into early
next week.

&&

.HYDROLOGY...
Issued at 0456 PM PST Wed Feb 5 2025

While the rain has ended, river flooding continues.  The Russian
River at Guerneville forecast has stabilized and is steadily
receding,and looks to go out of flood stage early Thursday. The
Next rain system arrives Thursday morning, with more moderate rain
rates expect into that afternoon. As of the current forecast, the
rainfall amounts don`t look to push the major rivers back into
flood stage, but smaller streams and urban areas could still have
some issues.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Flood Watch from Thursday morning through Friday afternoon for
     CAZ502>506.

     Frost Advisory from midnight tonight to 9 AM PST Thursday for
     CAZ506-510-516.

PZ...Small Craft Advisory from 9 AM Thursday to 3 AM PST Friday 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.

     Small Craft Advisory from 3 AM to 9 AM PST Thursday for Pt Pinos
     to Pt Piedras Blancas 0-10 nm.

     Gale Warning from 9 AM Thursday to 3 AM PST Friday for Pt Pinos
     to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Murdock
MARINE...RGass

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