832
FXUS66 KMTR 260851
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
151 AM PDT Wed Mar 26 2025

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

.SYNOPSIS...
Issued at 1245 AM PDT Wed Mar 26 2025

There`s a big shift in the weather today as the record breaking
heat is over and much cooler temperatures return. Several rounds of
rain are in the forecast over the next 7+ days as we enter a more
disturbed pattern.

&&

.SHORT TERM...
(Today and tonight)
Issued at 1245 AM PDT Wed Mar 26 2025

Our glimpse of summer weather was short lived with more seasonal
springtime temperatures returning today. The 00Z OAK sounding showed
an 850 mb temperature of ~16.4C which narrowly beats the previous
00Z record for March 26th (4PM March 25th) of 15.6C. This resulted
in record breaking warmth in the mid 80s to low 90s across the
region for the last two days. Why the change up to cooler
temperatures starting today? Well, the upper level ridge that has
been parked over the West Coast for the last few days is being
ejected eastward as an upper level trough and associated surface low
move in. The surface low will be located well to our north, closer
to Oregon and Washington, but a trailing cold front will extend
southward into Northern California. A look at forecast 850 mb
temperatures for today shows that they are expected to be around 10C
at 00Z March 27th (4PM March 26th). With cooler air being advected
into the Bay Area, temperatures will drop 15 to 20 degrees across
the region. For those wondering, how noticeable will this drop be?
Well, for example, Santa Rosa reached a high of 85 degrees yesterday
and is only forecast to reach a high of 64 degrees today. Farther
south, Hollister reached a high of 87 degrees yesterday and is
forecast to reach a high of 68 degrees today. This pattern holds
across the region with most locations expected to be in the 60s.

While the PNW is in for a rainy day as this low approaches,
residents of the Bay Area may see some precipitation Wednesday
ranging from light rain (North Bay) to drizzle (coastal areas south
of the Golden Gate Bridge). More rain from this system will arrive
Thursday with widespread light rain across the Bay Area. All in all,
the North Bay will see up to another 1" of rain from this storm and
areas south of the Golden Gate will see up to a quarter of an inch.
Winds will be locally gusty between 20 to 25 mph across the higher
elevations. The drop in temperatures and the return of rain are a
reminder that although summer is close, we aren`t quite there yet.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 1245 AM PDT Wed Mar 26 2025

By Thursday a decaying cutoff low pressure system near the
Pacific Northwest will be located poleward of the jet stream. This
system will essentially stall while continuing to fill through
Friday, but will still have enough strength to continue pumping
moisture to the Bay Area. The North Bay will see the highest rain
totals, with up to 1/2" possible Friday. The rest of the Bay Area
will see anywhere from a few hundreths to 1/4 inch or so.
Overall, this will be a mostly beneficial event. Some light rain
will likely linger Friday morning and the skies will begin to
clear breifly late Friday or early Saturday. After a short break,
the next system moves in as a triple point low develops somewhere
near the Bay Area Sunday. Overall the rain amounts will be around
1/4" or so for most of the Bay Area and Central Coast, outside of
the usual rain shadows (San Jose, San Benito, etc.).

The most interesting part of the forecast continues to be around
this time next week. By Tuesday, there is a chance that the jet
stream will be taking direct aim at the Bay Area. However, the
uncertainty remains very high. A look at the cluster analysis
reveals that we have roughly equal chances of ridging as
troughing, and even then the orientation of the potential trough
isn`t clear. The trend has definatley been flatter with the 500 mb
flow, which makes a true atmospheric river less likely. The CW3E
IVT forecast page shows a 60-70% chance of exceeding 250 IVT along
the coast on April 2, but less than a 25% chance of reaching 500
IVT. In summary, we are still expecting heavier rain next week,
but the impacts look more manageable lately. On the other hand,
it looks like there will be another round or two later in the
week. The first week of April looks wet. A multi-ensemble
analysis shows that in total by next Friday, SFO can recieve
anywhere from 0.5" to 2.5" of rain, with the mean around 1.25". We
can handle that.

&&

.AVIATION...
(06Z TAFS)
Issued at 1028 PM PDT Tue Mar 25 2025

A southerly surge of stratus and mist containing IFR ceilings and
visibility is continuing to push up to coast and into the
adjacent valleys. Winds will continue to diminish overnight
before a moderate to strong SW breeze moves in late morning before
some light rain in the afternoon at the northern terminals.

Vicinity of SFO...MVFR-IFR CIGs are possible tonight, but most of
the impacts will stay on the other side of the coastal mountains.
As the disturbance approaches, the marine layer will deepen,
allowing MVFR-IFR conditions later in the morning. This system
will also bring gusty SW winds and a chance for rain Wednesday
evening.

SFO Bridge Approach...Similar to SFO

Monterey Bay Terminals...IFR-LIFR conditions are firmly in place,
with no sign of relief overnight. By late morning, the ceilings
should start to break apart, and these terminals will not be as
affected by the weather up north through Wednesday afternoon.

&&

.MARINE...
(Tonight through next Monday)
Issued at 1028 PM PDT Tue Mar 25 2025

Foggy and drizzly conditions are expected across the waters
overnight. Light winds continue into the night before turning
southerly and becoming moderate to fresh into Wednesday. Seas will
flux between moderate and rough through Wednesday. Conditions
deteriorate Thursday when a west to northwest breezes become fresh
and seas become rough. Unsettled conditions continue through the
weekend and into the next work week as storm systems move through
the region.

&&

.BEACHES...
Issued at 1059 AM PDT Tue Mar 25 2025

A Beach Hazards Statement is in effect through Wednesday morning
for all Pacific Coast beaches. In addition to the cold water
shock risk that is always present, there will be an increased risk
for sneaker waves and rip currents. Observe the ocean for 20
minutes before you pick a spot on the beach, stay off of jetties
and rocks, keep pets on a leash, wear a life jacket, and never
turn your back on the ocean!

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement until 11 AM PDT this morning for CAZ006-
     505-509-529-530.

PZ...None.
&&

$$

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

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