High Surf in California, May 8, 2025

Area Forecast Discussion
National Weather Service San Francisco CA
134 PM PDT Thu May 8 2025

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

.SYNOPSIS...
Issued at 1214 PM PDT Thu May 8 2025

A warming trend will bring temperatures well above average Fri-Sat
before a cold front brings a sharp cool down starting Sunday and
a chance for rain Monday.

&&

.SHORT TERM...
(This evening through Friday)
Issued at 1214 PM PDT Thu May 8 2025

GOES visible imagery shows mostly clear skies away from the
immediate coast. Data from the Ft. Ord profiler is indicating the
marine layer has compressed to around 1,500 feet this afternoon
and this trend should continue as the 500 mb ridge builds over the
next 24 hours. As the ridge builds, the air mass will warm, with
a high likelihood that the 850 mb temperature exceed the 90th
percentile by late Friday. The ridge axis will extend from the
Channel Islands to the northern Rockies, bringing the 850 mb
temperature above 20C from Southern California to Montana. While
the Bay Area is escaping the core of the heating, interior
portions of Monterey and San Benito Counties will be more
directly affected. Temperatures are expected to reach the mid 90s
in the Southern Salinas Valley, and a Heat Advisory is in effect
from 10 AM Friday through 9 PM Saturday. The rest of the Bay Area
will enjoy some relief from onshore winds, which will keep
temperatures mostly in the 70s and 80s. For the forecast, we are
sticking with the 50th percentile of the NBM probabilistic
guidance for max and min temp. Focusing on the Heat Advisory in
the Southern Salinas Valley, most MOS guidance is around 5 degrees
warmer for Paso Robles than our forecast. You may even notice
something warmer than our forecast on your favorite weather app.
We've decided to stick with our blend as moderate onshore winds
should help bring a hint of marine influence to Greenfield and
King City, and the hourly temp forecast has been running warm
today.

&&

.LONG TERM...
(Friday night through next Wednesday)
Issued at 1214 PM PDT Thu May 8 2025

Saturday will be very similar to Friday with high temperatures
roughly 10 degrees above normal for inland areas and an ocean breeze
keeping the temperatures more seasonal along the coast. By Sunday
an approaching trough from the Pacific will clear out the ridge
and usher in a drastically different weather pattern for the next
few days. This trough will bring increased cloud cover and much
cooler temperatures, with some light rain expected Monday. Since
the modest moisture (PW around 0.7") arrives with the cooler air
mass, there may be some instability Monday, and we can't rule out
the possibility of a thunderstorm developing. Otherwise, most
areas have a slight to moderate chance of rain and could pick up
anywhere from a few hundredths to 1/4 inch, especially in the
North Bay and coastal mountains. While the rain forecast is still
a little fuzzy, one thing that is certain is the cooler
temperatures. The 850mb temp will crash from around 18C Saturday
to less than 5C by Tuesday morning. This will bring high
temperatures at the surface down anywhere from 10 to 15 degrees F
below normal, bringing some whiplash after a couple days well
above normal. The uncertainty has decreased substantially through
mid-week, and the progressive solution now has far more support in
the guidance. This means temperatures will gradually rebound back
toward normal as the trough evacuates to the East and ridging
rebuilds through mid-week. It also means the threat of an "inside
slider" pattern that can bring offshore winds and enhanced fire
weather conditions is becoming less likely.

&&

.AVIATION...
(18Z TAFS)
Issued at 1014 AM PDT Thu May 8 2025

High confidence. VFR conditions expected through the late evening.
The exception will be at KHAF where a shallow marine layer may hold
MVFR/IFR conditions through much of the day. Onshore winds will
increase this afternoon across most sites. By early Friday morning
confidence is lower for IFR/LIFR conditions to develop over KSTS and
MVFR/IFR to develop over the Central Coast sites. However, greater
confidence for the Bay Area Terminals to remain VFR as high pressure
builds over the region.

Vicinity of SFO...Onshore winds increase this afternoon with gusts
up to 25 kt. Higher confidence for Bay Area Terminals to remain VFR
tonight into Friday morning with easing winds.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Onshore winds increase this afternoon.
Winds ease late this evening and into the overnight hours. There is
moderate confidence of MVFR/IFR conditions returning early Friday
morning, so have included this in the TAFs.

&&

.MARINE...
(Today through Tuesday)
Issued at 905 AM PDT Thu May 8 2025

High pressure will build in from the north today and persist
through Saturday. As such, building high pressure will maintain
light to moderate northerly flow over the waters heading into the
weekend. Winds will be locally stronger north of Point Reyes and
along the Big Sur coast. Moderate seas continue through the end of
the forecast period.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 10 AM Friday to 9 PM PDT Saturday for CAZ516.

PZ...Small Craft Advisory until 3 AM PDT Friday for Pt Arena to Pt
     Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt
     to Pt Pinos 0-10 nm.

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

&&

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...RGass
MARINE...RGass

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