National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KMTR 221810
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1110 AM PDT Fri Sep 22 2023

...New AVIATION...

.SYNOPSIS...
Issued at 453 AM PDT Fri Sep 22 2023

Slight cooler than normal temperatures persist, with CPC outlooks
showing this pattern persisting through at least the next 14
days. A low pressure system moves in over the late weekend
potentially bringing beneficial rainfall to the North Bay zones,
then moving out by Tuesday.

&&

.SHORT TERM...
(Today and tonight)
Issued at 453 AM PDT Fri Sep 22 2023

A look at current temperatures across the region this morning show
lows largely in the mid to low 50s, with a handful of upper 40s
appearing in the North Bay region. Stratus coverage is largely solid
across the coastline, however much more sparse when looking inland,
where only the Northern Portion of Monterey Bay and Sonoma County
seem to have much of a stratus presence. Generally where stratus
coverage is present, temperatures are a few degrees warmer this
morning compared to the same time yesterday. Where stratus is
absent, temperatures are anywhere from 1 to 3 degrees cooler than
the same time yesterday, thanks to the allowance of radiative
cooling. Looking at winds, light conditions are being reported
through much of the region, though a bit of a southerly component is
seen this morning as a result of North-South gradients dominating
with +0.6mb from SFO to ACV, and -0.7mb from SFO to SMX.

Expectation through the day today is that stratus will clear from
the inland regions by the late morning, leading to clear skies
through the day. For the immediate coastline, stratus looks to
recede closer to the early afternoon before returning once again by
the early evening. Some smoke continues to linger through the day,
leading to hazy conditions. Otherwise, cooler than normal
temperatures are expected once again today and over the next
couple days with highs in the mid to upper 70s generally for
inland areas, and low 60s for coastal zones. On the other side of
the coin, lows tonight and over the next few days look similar to
what is being seen this morning, with generally widespread low to
mid 50s, with upper 40s in the North Bay valleys. Switching over
to take a look at winds - not much to write home about. Onshore
winds increasing to around 10mph into the afternoons are expected,
perhaps slightly breezier near the Delta as is typical in the
afternoons, then becoming light overnight.

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 453 AM PDT Fri Sep 22 2023

Looking a bit further out towards the latter half of the weekend and
into early next week, a low pressure system pushes into the region
from the PacNW, bringing rain chances primarily north of the SF Bay
region. Some slight chances of rain exist southward of this zone,
over the Monterey Bay area, though at this time, the most favorable
chances continue to persist over the North Bay zones. Additionally,
any measurable rainfall looks to be contained to the North Bay zones
as well. First chances of rainfall begin late Sunday evening, then
diminishing by early Tuesday morning. With that in mind, what are
the chances of receiving at least a quarter of an inch in North Bay
cities such as Santa Rosa and Petaluma? Currently 43 and 39%,
respectively. With it being more than a few days out from the event,
amounts are still uncertain, so stay tuned to the forecast for more
updates.

A glance at winds through the same time frame as the precipitation
chances show some slightly gusty conditions potentially developing
as the low and associated front moves in. Winds around 15mph are
expected, though gusts up to 20-25mph are possible over the North
Bay. Winds then diminish to become light again towards late Monday
evening. No wind products expected at this time. Elsewhere, not
expecting much in the way of elevated wind speeds.

Outside of precipitation chances, a look at CPC 6-10 and 8-14 day
temperature outlooks continue to hold our region in an below-normal
temperature pattern, bringing more fall-like weather.

&&

.AVIATION...
(18Z TAFS)
Issued at 1110 AM PDT Fri Sep 22 2023

Stratus continues to clear out and most of the region should see
clear skies in a couple of hours, barring some of the immediate
coast with ceilings throughout the TAF period. Smoke impacts will
diminish starting today through Saturday. Breezy westerly winds
will resume this afternoon with speeds up to 10-15 knots at the
terminals. Stratus starts to return this evening, with coverage
building through the night, before starting to mix out by the end
of the 24-hour TAF period.

Vicinity of SFO... VFR with breezy westerly winds up to 15 knots
this evening. Winds diminish overnight, with MVFR stratus for
several hours in the early morning. Stratus clears out by 17Z
Saturday followed by similarly breezy west winds during the
afternoon.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... Stratus expected to clear out by 19Z at
SNS and by 20Z at MRY with VFR conditions during the day. Onshore
westerly winds are helping to keep stratus at MRY a little longer
than at SNS. ASOS stations at SNS and MRY are both reporting
haze/smoke which may temporarily impact visibilities throughout the
day. Winds will be breezy during the afternoon but will slow back
down by the late evening. MVFR conditions will return in the late
evening/overnight with overcast conditions returning to MRY and
SNS beginning between 07-08Z.

&&

.MARINE...
(Today through Wednesday)
Issued at 1051 AM PDT Fri Sep 22 2023

Gentle to moderate north breeze persists through the weekend. A
quickly strengthening low pressure system will bring light rain
chances to the northern waters Sunday through Tuesday. Otherwise,
northwesterly swell diminishing through the evening with a new
swell train arriving late into the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...AC
LONG TERM....AC
AVIATION...DialH/Kennedy
MARINE...DialH

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea