974
FXUS66 KMTR 150830
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1230 AM PST Wed Jan 15 2025

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

.SYNOPSIS...
Issued at 1054 PM PST Tue Jan 14 2025

Mostly clear skies, dry weather, light winds, cold mornings and
mild afternoons will continue through the week.

&&

.SHORT TERM...
(Tonight through Thursday)
Issued at 1054 PM PST Tue Jan 14 2025

While low elevation temperatures are running a degree or two
colder than 24 hours ago, surface dew points are around 5 degrees
higher than last night. This will put a limit on the cooling
tonight, as moist air cools much less efficiently than dry air.
As a result, the minimum temps will be a few degrees higher than
yesterday and there may be some mist in the air near river
valleys. Despite this, it will still be a chilly start across the
Bay Area and Central Coast with temperatures dropping into the
upper 30s and low 40s across the Bay Area, and down to the low 30s
across inland portions of the Central Coast. After the chilly
start, it will be another beautiful day with plenty of sunshine,
high temps in the 60s and light winds.

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 1054 PM PST Tue Jan 14 2025

There are some interesting developments in the long term forecast.
The overall pattern continues to be dominated by high pressure
offshore, and Wednesday and Thursday will be very similar to
the previous few days. By Friday, a weak cold front will move
through from the north, bringing cooler temperatures and some
clouds (no rain) back to the Bay Area skies. The 1000-500 mb
thickness and 850 mb temperature will only drop slightly, but the
disturbance will bring the return of onshore flow, and even a
marine layer. Remember the marine layer? The cold front will also
cause the max and min temps to drop, and more widespread frost
advisories are expected this weekend into early next week. The
onshore wind won`t last long. While the uncertainty balloons by
Saturday, it looks like there will be a return to offshore winds.
There is now a bi-modal solution in the ensemble guidance
regarding how strong these winds will be. The deterministic SJSU
2km WRF with GFS boundary conditions shows the SFO-WMC gradient
dropping below -18 mb by Monday. This would bring critical
offshore winds with hydraulic jumps and gusts in the 60-80 mph
range. However, a peak at the ensemble solutions show roughly 50%
support for this high end event, with the other members much less
aggressive, huddled around -4 mb. There are no solutions in the
vast gap between these two. This makes the forecast extremely
tricky. On one hand, it might make sense to split the difference
and go with the ensemble mean. The problem is that the mean has no
support in the individual solutions. The other option is to pick
one of the 2 extremes and message the uncertainty. That`s what we
will do for now. I am going with the weak scenario since it has
been more consistent in previous model runs. However, this new
emerging solution is too strong to ignore, so we will begin
messaging the possibility of very strong offshore winds. Just know
it can still go either way. While there is plenty of time for the
guidance to change, right now it looks like the winds will either
be gentle or just about as strong as they get on Monday. Stay
tuned.

If you`re here to see if it`s going to rain anytime soon, it`s
not. We`re looking dry through the end of next week, at least.

&&

.AVIATION...
(06Z TAFS)
Issued at 938 PM PST Tue Jan 14 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.


Vicinity of SFO...VFR through the TAF period. Moderate northwest
winds last into the late night before becoming light and variable
for Wednesday morning and through that afternoon. Additional moderate
northwest winds arrive Wednesday evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Moderate
northwest winds weaken into the night and turn into southeast
drainage winds overnight. These winds will arrive later into the
night for SNS, but will be more moderate compared to the lighter
winds at MRY. Expect moderate northwest winds to return mid
Wednesday afternoon.

&&

.MARINE...
(Tonight through next Monday)
Issued at 938 PM PST Tue Jan 14 2025

Expect light northerly winds continue through the end of the week
with abating seas. The Sea state will be low with moderate period
into the weekend, but look to build over the weekend as breezier
winds return.

&&

.BEACHES...
Issued at 800 PM PST Tue Jan 14 2025

Moderate period northwest swell will gradually subside through
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 until 9 AM PST Wednesday for CAZ516>518.

PZ...None.
&&

$$

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

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