National Weather Service

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

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323
FXUS66 KMTR 292120
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
Issued by National Weather Service Eureka CA
220 PM PDT Tue Apr 29 2025

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

.SYNOPSIS...
Issued at 218 PM PDT Tue Apr 29 2025

Another fair weather day across the board today. Nice again tomorrow with a slight chance
for very isolated showers and thunderstorms (see discussion for more targeted info). Otherwise
quiet conditions remain until the weekend where we can expect soggy conditions along with
gusty winds.|

.SHORT TERM...
(This evening through Wednesday)
Issued at 218 PM PDT Tue Apr 29 2025

Splendid day today with nearly cloudless skies, sans a few areas along the immediate coast.
Temperatures as expected today with temperatures ranging from the upper 60s to upper 70s. Some
locations along the coastline held on to marine stratus for a bit longer today, so these locations
are just getting out of the upper 50s as of writing. Shifting focus a bit to tomorrow since there
some more interesting things to talk about. A subtle upper level trough is progged to move
through the region tomorrow which will bring a low chance of very isolated showers and thunderstorms
to the North Bay and areas near Monterey and San Benito counties in the vicinity of the Gabilan
Range. Cold air advection in the upper levels with the passage of the trough and hi res guidance
depicting sufficient low level moisture advection result in moderate instability of ~1,000 J/Kg.
Rather impressive for this time of the year, but not unheard of. Areas of interest in this event
would be favored areas of terrain-enhanced convection, such as interior portions of the North Bay
and the interior Central Coast along the Gabilan Range. Limiting factors for severe modes will be
the relative lack of a lifting mechanism and overall low degree of instability throughout the layer
(slightly unstable through a deeper column as opposed to highly unstable through a shallower column).
Should our available instability be realized through lifting via diurnal heating over these isolated
terrain areas, we could see brief heavy showers and perhaps some small hail...again emphasizing
isolated to the aforementioned areas.

.LONG TERM...
(Wednesday night through next Monday)
Issued at 218 PM PDT Tue Apr 29 2025

Once again not much to talk about between Wednesday and Friday, so shifting focus to the weekend.
We have increased attention towards the weekend event regarding windy conditions. A deep upper
low progged to enter the NEPac by Friday afternoon will bring quite a contrast to what we are going
through mid-week. Increased cloudiness and breezy conditions will begin affecting the region late
Friday. Winds increase on Saturday as a stout 75-80 kt 500 mb jet streak digs south along the West
Coast. Behind the cold front we can expect wind gusts into the 40-50 mph range across some of the
high coastal terrain. Ensemble forecast tools corroborate this
with the ECMWF extreme forecast index showing a good agreement of
model members well above climatology and cluster analysis
advertising solid agreement in the overall pattern. As such, winds
have been nudged toward the 75th percentile in the forecast for
late Friday night through Sunday. Judging based on the forecast
trend, winds could be adjust higher in future forecast packages if
the trend continues. Keep up with the latest forecasts for the
most up to date information as the timeline moves closer.

.AVIATION...
(18Z TAFS)
Issued at 1047 AM PDT Tue Apr 29 2025

Solid marine layer this morning led to cigs and dense fog. Over
the last hour or two conditions have improved except for the
immediate coast. Expect mainly VFR this afternoon with IFR to MVFR
impacting the immediate coastline. Tonight will feature another
night of marine layer intrusion, but the lower confidence is how
much. Hi-res guidance develops some offshore flow at 2500 ft,
which will battle the level moisture intrusion. That being said,
did allow for some lower cigs, but later with early clearing on
Wednesday.

Vicinity of SFO...VFR this afternoon with onshore flow. Cigs come
back 08-10Z, but thin/clear during the AM rush Wednesday.

SFO Bridge Approach...Similar to SFO. Expect some cigs again
tonight, especially E side.

Monterey Bay Terminals...KSNS is VFR, but KMRY is holding onto
LIFR with slow clearing. Feeling optimistic with clearing for
KMRY by 19Z. Cigs do return this evening and lingering through
Wednesday.

.MARINE...
(Today through Sunday)
Issued at 1047 AM PDT Tue Apr 29 2025

High pressure over the East Pacific will maintain strong
northwesterly winds through Wednesday. The strongest winds will be
over the outer waters with near- gale force gusts along with
rough seas. Moderate seas and moderate northwesterly breezes will
prevail Thursday and Friday. Strong northwesterly breezes and
rough seas return Saturday to the outer waters.

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 AM PDT Wednesday for Pt Arena to Pt
Reyes 0-10 nm.

Small Craft Advisory until 3 AM PDT Thursday for Pt Arena to Pt
Reyes 10-60 NM.

Small Craft Advisory until 3 PM PDT Wednesday for Pigeon Pt to
Pt Pinos 10-60 NM.

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...MM
MARINE...MM

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