516
FXUS66 KMTR 160017
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
417 PM PST Wed Jan 15 2025

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 1256 PM PST Wed Jan 15 2025

Very quiet once again today, as will be the case through this
weekend. Potential for some local fog early this weekend around
coastal areas, and the potential for offshore winds early next
week.

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 1256 PM PST Wed Jan 15 2025

Absolutely gorgeous day today under clear skies and very little
wind. A slight offshore gradient still exists where the mean flow is
easterly due to lingering high pressure over the Great Basin and a
nearly stationary upper low well off the coast of Baja. This pattern
continues tomorrow before the upper low finally starts to move
inland.

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 1256 PM PST Wed Jan 15 2025

A look at the long term period provides a bit more to talk about and
an frustrating level of uncertainty. Once the aforementioned upper
low moves inland, a broad upper ridge develops over the West Coast
and largely remains in place through the extended period. The
biggest question mark right now is how much a deep trough will dig
into the central US, whether or not a new cut off low will develop
from it in the Desert SW, and how strong that cut off low may be. As
it stands currently, there is considerable uncertainty in an
offshore wind event late this weekend and early next week. High
confidence that we will not see any rain, and the ridge will
dominate the pattern, but low confidence on if we will see impactful
offshore winds or not. Per latest hi-res WRF ensemble guidance,
there is a bimodal distribution after this weekend regarding the
strength of the SFO-WMC (San Francisco to Winnemucca, NV)
pressure gradient. Nearly half of ensemble members advertise a
neutral or slightly onshore gradient, whereas the other half of
members advertise an offshore gradient near the 90th percentile,
which means the potential for moderate offshore winds. Likewise,
if we zoom out to larger scale global models which include more
ensemble members, there is nearly an even distribution of
solutions varying from basically light wind and fair weather to
moderate offshore winds. Based on the lack of rain in the forecast
and the fact that the Energy Release Component of grasses and
shrubbery in the Central Coast is nearing the 80th percentile, we
will begin increasing messaging regarding the potential for at
least some fire weather impacts for southern areas next week.
However, based on the large amount of uncertainty, it would be
wise to pay close attention and stay up to date with the forecast
for the latest information.

&&

.AVIATION...
(00Z TAFS)
Issued at 416 PM PST Wed Jan 15 2025

VFR through the TAF period for all but the North Bay which will see
some pockets of fog overnight. Winds mostly stay light to moderate
with local effects driving most of the wind directions though the
TAF period. Winds around the Monterey Bay will be slightly more
unified as overnight southeast drainage winds affect the area and
last through much of Thursday morning.


Vicinity of SFO...VFR through the TAF period. Moderate northwest
winds build in the evening and last into the late night before
becoming light and variable and lasting through mid Thursday
afternoon. Additional moderate northwest winds arrive late Thursday
afternoon.


SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Expect mostly
light to moderate winds through the late night, with moderate
southeast drainage winds arriving in the late night and early
Thursday morning. These winds linger through the morning before MRY
turns light and variable, and more moderate northwest winds affect
SNS into the mid afternoon.


&&

.MARINE...
(Tonight through next Tuesday)
Issued at 416 PM PST Wed Jan 15 2025

Light and variable winds will continue over the coastal waters and
will turn more northerly into the late night. Northerly winds
increase on Friday will result in a modest building of seas for
the weekend.

&&

.BEACHES...
Issued at 322 AM PST Wed Jan 15 2025

Still some energetic surf zone early on Wednesday with a moderate
period northwest swell. The northwest swell will gradually
subside later Wednesday. There is a slight risk of sneaker waves.
Remember to never turn your back on the ocean.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory from 1 AM to 9 AM PST Thursday for CAZ516>518.

PZ...None.
&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Murdock
MARINE...Murdock

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