Altadena, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

173
FXUS66 KMTR 112335
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
435 PM PDT Sat Apr 11 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 109 PM PDT Sat Apr 11 2026

 - Rain showers and isolated thunderstorms are forecast to
   increase this afternoon and evening

 - Rain showers and thunderstorm chances linger into Monday morning

 - A warming and drying trend returns through the remainder of
   the work week

&&

.SHORT TERM...
Issued at 109 PM PDT Sat Apr 11 2026
(This evening through Monday)

Rain showers and isolated thunderstorms remain in the forecast
through early afternoon. Then, as a surface low approaches the
northern California coast, a narrow cold-frontal rainband (NCFR) is
forecast to approach the North Bay between 2 PM - 5 PM, 4 PM - 7 PM
across the Bay Area, and 6 PM - 9 PM across the Central Coast. Along
and ahead of the NCFR is when we have the greatest potential for
damaging wind gusts exceeding 40 kt out over the ocean and bays.
This will also be when we have the greatest potential for rotating
cells that may produce waterspouts and/or weak tornadoes. Wind gusts
are also expected to reach up to or exceed 50 mph along the coast
and in the higher terrain during the aforementioned timeframes. Any
stronger convection will be capable of producing stronger wind
gusts. Again, much of our region remains under a Marginal Risk for
sever weather today.

The aforementioned low pressure system is forecast push into
northern California later tonight and become quasi-stationary
through Sunday. Thus, scattered to numerous rain showers and
isolated thunderstorms will prevail through Sunday and into early
Monday morning as a colder/unsettled air mass moves into the region.
This colder air mass will result in a low end potential for the
region`s highest peaks to see snowfall through Monday morning.
However, little to no snow accumulations are forecast at this time.

&&

.LONG TERM...
Issued at 109 PM PDT Sat Apr 11 2026
(Monday night through next Friday)

The colder air mass will result in chilly temperatures across the
interior both Monday and Tuesday mornings especially over the North
Bay Valleys and interior Central Coast. Temperatures are currently
forecast to be in the low-to-upper 30s in these areas with low 40s
to near 50 degrees F elsewhere across the region. There is the
potential for frost each morning across these interior regions,
especially in the wind sheltered areas. Temperatures rebound to near
seasonal averages by Thursday and Friday as ridging builds in from
the eastern Pacific.

&&

.AVIATION...
(00Z TAFS)
Issued at 434 PM PDT Sat Apr 11 2026

The forecast remains challenging for the TAF period with a frontal
rain band currently coming into the region. Within the North Bay and
San Mateo Peninsula, MVFR-IFR conditions are in place with steady
rainfall through the band. Ahead of the rainband, across the
interior East Bay and South Bays and the Central Coast, a mixed band
of VFR to MVFR conditions prevails as isolated to scattered showers
persist. Expect increasing southerly winds through the next few
hours as the most intense rain approaches the region through 06Z,
with IFR conditions and gusts to 30-40 kt expected. Behind the
frontal rain band, gradual improvement is expected, although winds
remain gusty and scattered showers continue through the end of the
TAF period. Overall forecast confidence remains low to moderate.

Vicinity of SFO... Gusty southeast to south winds in addition to wet
runways will make for challenging conditions at the terminal this
evening into Sunday. Low-end VFR to MVFR conditions at present as
the terminal sits in the frontal rain band. The most intense
conditions are expected within the next couple of hours as the
frontal rain band approaches, with gusts of 30-35 kt expected as it
passes through. Will also need to monitor chances for lightning as
well. Steady rain will transition to more scattered showers through
the overnight hours into Sunday.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... VFR-MVFR conditions through the next few
hours with the approaching rain band coming into the region. Most
intense rain is expected to arrive around 03-04Z, accompanied by
MVFR-IFR conditions and the gustiest south to southwest winds of
around 20-25 kt. Overnight, steady rain will transition to
scattered showers through the end of the TAF period. Winds will
generally be rather gusty from the southwest through the night,
with some LLWS concerns at SNS as surface winds decouple from the
flow aloft.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 434 PM PDT Sat Apr 11 2026

Dangerous conditions will exist over the coastal waters through
this evening as a potent line of storm moves through. Stronger
developed storms will be capable of producing gusty winds,
lightning, brief heavy rain, and a waterspout. Conditions will
gradually improve overnight, but scattered showers and locally
gusty winds remain through Sunday. High pressure builds behind
the system with fresh northwest winds developing early next week,
as seas abate to become moderate through mid week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 PM PDT Sunday for Mry Bay-Pt Reyes
     to Pigeon Pt 0-10 nm-SF Bay N of Bay Bridge.

     Small Craft Advisory until 9 PM PDT this evening for Pt Arena to
     Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory until 9 AM PDT Sunday for Pigeon Pt to Pt
     Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Pinos to Pt
     Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...DialH
MARINE...MM

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