Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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000
FXUS66 KMTR 171128
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
428 AM PDT Sun Mar 17 2024

...New AVIATION...

.SYNOPSIS...
Issued at 349 AM PDT Sun Mar 17 2024

Clear afternoon skies and pleasant temps persist into the middle
of the week. Subtle return of stratus during the early mornings
to favored coastal and valley locations. Wet and chilly pattern
returns by the end of the week and weekend.

&&

.SHORT TERM...
(Today and tonight)
Issued at 423 AM PDT Sun Mar 17 2024

Satellite and surface observations show patchy valley fog and low
clouds otherwise it`s clear early this morning. Under mid March
sun, afternoon temperatures will warm a few to several degrees
above mid March normals reaching the 60s coastside and bayside and
the 70s inland. Lows tonight and Monday morning cooling to the 40s
inland to near 50 coastside and bayside.

&&

.LONG TERM...
(Monday through Saturday)
Issued at 423 AM PDT Sun Mar 17 2024

A strong, stationary long wave ridge remains over the Pacific
Northwest which will soon slowly begin retrogressing reaching
Alaska later this week. A Rex Block synoptic pattern with a
stationary, closed 500 mb low over southern California and the
Desert Southwest south in latitude of a stationary, closed 500 mb
high (in the long wave ridge) over the Pacific Northwest will
begin breaking down Tuesday. 500 mb troughing will consolidate
over the eastern Pacific during the week while the long wave ridge
retrogresses. This pattern set up becomes important for late week
and weekend.

Astronomical spring 2024 arrives 0306Z March 20th (8:06 pm PDT
Tuesday, March 19th) however the large scale pattern is forecast
to remain winter-like through the end of March. The polar jet
stream is wavy and broken up over the eastern Pacific, however
based on model forecasts the polar jet over the western and
central Pacific is forecast to undercut the aforementioned higher
latitude ridge over Alaska this weekend; a sign of winter strength
if it verifies. The ongoing cool phase of the Pacific Decadal
Oscillation, current western U.S. snow cover and southern U.S.
subtropical jet may help grease the wheels for another round of
wintry precipitation. There`s at least good model agreement out
through 120 hours (late Thursday) with 500 mb troughing approaching
the Bay Area and north Central Coast from the west, rain arriving
Friday. The upcoming weekend looks wet and chilly, it could be
cold enough for wet snow on the highest peaks in our forecast
area. Northerly surface winds across the Bering Sea at first and
then later this week across southwestern Canada will usher in a
colder air mass that will merge with a slowly gathering plume of
water vapor with precipitable water near 1" extending northeastward
from the subtropics late this week that as mentioned will bring a
return to wet and chilly weather in our forecast area. At this
time rain looks mainly beneficial vs hazardous.

&&

.AVIATION...
(12Z TAFS)
Issued at 428 AM PDT Sun Mar 17 2024

Patchy fog and stratus across the North Bay and San Mateo coasts,
the Sonoma County valleys, the East Bay Hills, and the southern
Salinas Valley. These patches are building towards the south, with
further development expected through the rest of the night into
morning, but with low confidence on spatial extent, especially along
the Central Coast. VFR with light to breezy onshore flow returns
this afternoon. More widespread stratus develops tonight into Monday
morning.

Vicinity of SFO... Light winds through the course of the night. Not
expecting SFO to develop a reduced ceiling tonight as the stratus
flows through the Golden Gate and into the eastern SF Bay. OAK has
slightly more confidence of stratus impacts in another hour or so.
Breezy northwest winds return this afternoon with more expansive
stratus expected tonight into Monday morning.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... Stratus has mixed out for now, and
currently monitoring stratus off the San Mateo coast for any impacts
to the region. Confidence is low for any impacts, which would happen
around 16-18Z if stratus does redevelop over the terminals this
morning. As a result, have removed the prevailing ceilings from the
TAFs, but will continue to monitor. VFR conditions and light onshore
winds expected by the afternoon, with a more contiguous stratus deck
developing tonight.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 224 AM PDT Sun Mar 17 2024

Moderate to fresh northwesterly breezes develop later today with
strong gusts, hazardous to small craft, possible in the coastal
jet regions. Winds diminish this evening with generally gentle to
moderate winds through the next week. Moderate period northwest
swell continues to diminish through the weekend with another
light northwest swell arriving Monday.

&&

.CLIMATE...
Issued at 118 PM PDT Sat Mar 16 2024

Taking a breather from the rainfall events, it`s a good time to
pull some stats. Here`s a look at where a few sites are for
rainfall so far this water year (10/1/23 to 3/15/24), as well
as a comparison to where we were at this point last year.

Site                    Normal          2023-24         2022-23

Santa Rosa (Co-op)      25.99"          28.35"          38.38"
Napa State Hospital     21.79"          20.19"          28.27"
Kentfield               37.17"          38.63"          53.63"
San Francisco Dwntn     18.78"          21.95"          28.62"
Oakland Dwntn           18.67"          17.46"          31.10"
Redwood City            15.76"          15.21"          30.08"
Fremont                 12.81"          14.97"          25.43"
Livermore (Co-op)       11.71"          12.24"          22.39"
Salinas                 10.14"          10.61"          13.06"
Monterey                13.20"          13.04"          20.56"
King City                9.69"          13.13"          16.56"

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this
     evening for Pt Arena to Pt Reyes 0-10 nm.

&&

$$

SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...DialH
MARINE...DialH

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