FXUS66 KMTR 102328
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
428 PM PDT Fri Apr 10 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1220 PM PDT Fri Apr 10 2026
- Rain and thunderstorms through the weekend
- Gradual warming and drying trend next week
&&
.SHORT TERM...
Issued at 1220 PM PDT Fri Apr 10 2026
(This evening through Saturday)
A mid/upper level low pressure system remains about 100 miles off of
the northern California coast. This feature has resulted in
widespread rain showers across our region the past 24 hours with the
North Bay picking up between 0.25"-1.25". Lesser amounts have been
reported south of the North Bay, but some coastal and mountain
locations have received up to 0.75". Overall, this has been greater
than originally forecasted. This band of rain showers continues to
shift inland and the threat for rain showers and thunderstorms will
persist throughout the afternoon and evening, especially as day time
heating increases surface based CAPE to between 500-1000 J/kg. Any
thunderstorm will be capable of producing lightning, locally heavy
rainfall, erratic/gusty winds, and small hail. Weak low-level wind
shear does not support a mention of rotation that would lead to
tornadoes and/or waterspouts through this evening. Rain showers and
a slight chance of thunderstorms will continue into the night, yet
chances for both trend downward overnight.
An approaching mid/upper level low is forecast to drop out of the
Gulf of Alaska on Saturday and move inland Sunday afternoon across
northern California. This is when we have all three ingredients for
thunderstorms: lift, instability, and moisture. Some of the higher
resolution and conviction-allowing models (CAMs) such as the RRFS
indicate the potential for a narrow cold-frontal rainband (NCFR) to
move across the Bay Area and Central Coast Saturday afternoon and
evening. This will be when we have the greatest potential for
rotating cells that may produce waterspouts and/or weak tornadoes.
In coordination with the Storm Prediction Center, we have been
upgraded to a Marginal Risk of severe thunderstorms on Saturday. The
greatest potential being the threat of wind exceeding 40 knots.
From previous forecaster: "Anglers should take special note of the
expected weather and have a plan to reach safe harbor quickly when
the weather turns. Even without thunderstorms, the marine conditions
will deteriorate through the day Saturday. If thunderstorms develop,
the associated wind gusts are capable of capsizing small vessels.
Fishing leads to more lightning deaths in the U.S. than any other
activity. When thunder roars, head indoors!"
&&
.LONG TERM...
Issued at 1220 PM PDT Fri Apr 10 2026
(Saturday night through next Thursday)
The rainfall amounts continue to trend higher today through Sunday
with 0.50"-0.75" in the southern Salinas Valley, 1"-2" across much
of the Bay Area and Central Coast, and up locally up to 4" in the
coastal ranges. However, this rainfall will be mostly beneficial
with no widespread river flooding anticipated. However, we can still
see ponding of water on roadways, minor urban and small stream
flooding, and flooding of poorly drained areas. This will be
especially so if any heavier showers and/or thunderstorms develop
and train over any one given area.
Post-frontal rain showers and isolated thunderstorm will continue
into Sunday as a colder air mass settles into the region. This is
when we may see snow fall across the higher peaks across the region,
however little to no snow accumulation is expected. Lingering rain
showers and isolated thunderstorms may persist into early Monday
morning before a warming and drying trend resumes by Monday
afternoon. Slightly below normal temperatures are expected Monday
afternoon before rebounding to near seasonal averages by Thursday
and Friday.
&&
.AVIATION...
(00Z TAFS)
Issued at 428 PM PDT Fri Apr 10 2026
Conditions across the region remain rather messy as convective
showers, with some isolated thunderstorms, develop across the
interior regions, but the terminals are generally VFR with ample mid-
to high cloud cover. Winds are generally from the south and
southwest with the potential for strong gusts, especially in favored
regions and the vicinity of thunderstorm development. In general,
wind speeds and storm coverage will gradually diminish after sunset
and through the overnight hours, with showers returning on Saturday.
Southwest winds will increase through Saturday, with a narrow cold
frontal rain band (NCFR) approaching the region towards the end of
the 24-hour TAF period. While this NCFR will bring the strongest
gusts and most intense precipitation, higher than those in the
forecast, opted to not try to time out the NCFR arrival with this
issuance.
Vicinity of SFO... VFR conditions with mid- to high level clouds and
a chance for showers continue through the day. MVFR conditions will
develop early Saturday morning with the some showers through the
morning, with ceilings lifting to VFR after sunrise. Winds will come
from the southwest through the TAF period, with the winds
dramatically strengthening through Saturday afternoon and evening as
the narrow cold frontal rain band approaches the terminal. Wind
gusts of 35 kt or above as the NCFR passes can not be ruled out.
Winds will slightly diminish once the NCFR passes, with showers
continuing around the terminal area.
SFO Bridge Approach... Similar to SFO.
Monterey Bay Terminals... VFR conditions with mid- to high level
cloud cover and scattered showers through the evening hours. MVFR
conditions are possible early Saturday morning, with VFR conditions
returning after sunrise. Showers will come into the region on
Saturday morning, with the narrow cold frontal rain band expected
after the end of the TAF period. Winds will come from the southwest
through the TAF period, with breezy winds through the evening, winds
becoming gentle overnight, and breezy winds with strong gusts
returning Friday afternoon.
&&
.MARINE...
(Tonight through next Wednesday)
Issued at 428 PM PDT Fri Apr 10 2026
Isolated to scattered showers and a chance of thunderstorms remain
in the forecast today. The next round of precipitation arrives
late Saturday into Sunday, as the next weather system arrives.
Increasing winds are expected, with isolated gale force gusts
from Pigeon Point to Point Pinos. High pressure builds behind the
system with fresh northwest winds developing early next week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM to 9 PM PDT Saturday for Mry Bay-
Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras
Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm-SF Bay N of
Bay Bridge.
Small Craft Advisory from 9 AM to 3 PM PDT Saturday for Pt Arena
to Pt Reyes 0-10 nm.
Small Craft Advisory from 3 PM to 9 PM PDT Saturday for Pigeon
Pt to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...RGass
LONG TERM....RGass
AVIATION...DialH
MARINE...KR
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Prepared by Boulder-Creek.com Weather at: Fri Apr 10 18:30:03 PDT 2026
From the National Weather Service
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