Pacifica, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

857
FXUS66 KMTR 241920
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
Issued by National Weather Service Eureka CA
1220 PM PDT Thu Apr 24 2025

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

.SYNOPSIS...
Issued at 1217 PM PDT Thu Apr 24 2025

Cool and cloudy conditions will grip much of the Bay Area and
Central Coast through the first half of the weekend. There`s an
opportunity for light rain and a rumble of thunder or two, late
Friday and into Saturday. The favored regions for rain and
isolated storms will be across the Central Coast and adjacent
offshore waters. Thereafter, rain-free conditions are forecast.

&&

.SHORT TERM...
(This afternoon through Friday Night)
Issued at 1217 PM PDT Thu Apr 24 2025

Short Term Key Messages
-Cool and cloudy conditions persist
-Rain chances increase late Friday

The marine layer has established itself across the region and it`s
quite a stark contrast from 24 hours ago. Widespread cloud cover
has been noted on the latest satellite presentation, though inland
areas and regions of terrain are clearing very gradually.

With broad mid-level troughing encouraging more in the way of
onshore flow, I anticipate clearing will be short lived and for
some regions, especially along the coast, mostly cloudy skies will
prevail. We`ll be locked into this onshore flow regime through at
least Saturday, and the forecast will remain on the cool side as
a result. As it pertains to rain chances, it appears that a bulk
of the "heavier" precipitation won`t arrive until after 00 UTC
Saturday or 5pm Friday. Prior to that, pockets of drizzle are
forecast with perhaps a few areas measuring a few hundredths of an
inch. If the forward speed of the upper system accelerates, then
more widespread rainfall will be on the table earlier in the
evening on Friday.


&&

.LONG TERM...
(Saturday through next Wednesday)
Issued at 1217 PM PDT Thu Apr 24 2025

Long Term Key messages
-Rain and isolated thunderstorms forecast
-High elevation snow (Santa Lucia and Diablo Ranges)
-Warmer and largely rain-free Sunday onward

The main upper low will pinwheel just west of the Southern
California Bight on Saturday. Forecast 700-500mb lapse rates
should approach 7 to 7.5 C/km across the marine areas and
southern Monterey County beneath the cold pocket associated with
the upper low. This translates to a few hundred joules/kg of CAPE,
though the max CAPE resides across SLO and points southward. The
positioning of the low does modulate the thunderstorm risk. If the
low slides more to the south, then the pocket of cooler air aloft
will be farther displaced from our area, thereby lowering the
isolated thunderstorm risk. If the upper low remains a bit farther
north, then a greater portion of the Central Coast will be at a
greater risk for isolated storms. Currently the primary hazard
would be isolated lightning strikes. Brief accumulating hail
cannot be discounted, especially with any of the more vigorous
showers and/or storms.

Overall, rain amounts will be beneficial, especially across the
Central Coast. This area largely missed out on some of the more
robust AR events from this past year and this rain will at least
mitigate the fire weather threat initially. Rain amounts will be
quite respectable, given the time of year and amounts will average
between a few tenths of an inch to perhaps as great as 1/2 inch.
In fact there`s around a 50% chance that some parts along the Big
Sur Coast/Santa Lucia Range may see between 1/2 to 3/4 of an inch
of rain.

But wait...there`s a little bit more. Some of the higher peaks of
the Santa Lucia and Diablo Ranges may even get a bit more than
"novelty" snowflakes as blended guidance suggests around a 50%
chance for 2" of snow. At this time, no plans for any winter
headlines as snow will be across a very confined to the highest
peaks, but if snow levels come in a little lower, we may need to
consider stronger messaging/wording.

Saturday evening through the remainder of the extended forecast
appears that it`ll remain quiet. This is supported with agreement
among the various model solutions with ridging taking shape.
Moreover, longer term model predictions support odds leaning
toward warmer and drier than normal conditions precip.

&&

.AVIATION...
(18Z TAFS)
Issued at 1057 AM PDT Thu Apr 24 2025

MVFR cigs are expected to persist through most of the forecast
period with increased chances of VFR late in the period by mid-
morning Friday with an increase in mixing as the upper level low
continues to approach from the north. Expect periods of drizzle
along coastal sites tonight through early Friday morning as well.
Breezy to gusty onshore flow will also increase as the upper
level system approaches.

Vicinity of SFO...MVFR is expected to prevail through the
forecast, however there is a chance of enough mixing for a window
of VFR conditions this afternoon into early evening. Onshore
winds will increase this evening becoming breezy as the upper
level low approaches from the north. VFR chances increase toward
the end of the TAF period late Friday morning.

SFO Bridge Approach...Similar to SFO

Monterey Bay Terminals...Expecting MVFR cigs to persist through
the forecast period. There is a chance for VFR conditions this
afternoon into the early evening, however current trends show a
steady fetch of moisture rich onshore flow limiting that
possibility. Patchy fog and drizzle are possible later tonight
through Friday morning as well.

&&

.MARINE...
(Today through Tuesday)
Issued at 945 AM PDT Thu Apr 24 2025

Expect quiet weather for the rest of today with some light rain
moving across the waters starting Friday morning and lingering
into that night. Strong northwesterly breezes and rough seas
return late Saturday.

&&

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

$$

SHORT TERM...Bain
LONG TERM....Bain
AVIATION...JM
MARINE...KR

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