Simi Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

045
FXUS66 KLOX 170555
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1055 PM PDT Wed Sep 16 2026

.SYNOPSIS...16/1053 PM.

Generally quiet weather expected with cooler than normal
temperatures and a robust marine layer today. Slight warming and
a shrinking marine layer are expected Friday into the weekend.

&&

.SHORT TERM (WED-SAT)...16/842 PM.

***UPDATE***

Thanks to a very deep marine layer today, some areas struggled to
clear (mainly near the mountains south of Point Conception), but
the remainder of the region saw sunny afternoon skies. The
majority of the region saw a few degrees of cooling compared to
yesterday, with highs in the high 60s to 70s along the Central
Coast, and 70s to low 80s elsewhere. These temperatures are quite
a bit below normal, around 5 to 10 degrees, locally 15 degrees
below normal away from the coast for this time of year. At the
coast, however, temperatures were within a few degrees on either
side of normal.

Another round of deep marine layer clouds are expected overnight
into tomorrow morning, with better late morning clearing compared
to today (thanks to a slight decrease in onshore flow).
Temperatures will be similar to today, with only a few degrees
different.

Forecast looks to be in shape and no evening updates were needed.

***From Previous Discussion***

Thanks to the influence of the upper level low to our north and
the persistent onshore flow, an extremely deep marine layer
brought a June Gloom day to us here in Southwest California in
mid-September. We`re expecting another night of a fairly robust
marine layer which will bring another gray morning to most folks,
likely with better clearing tomorrow compared to today.

Only minor changes for tomorrow`s temperatures, then a slight
warming trend will occur Friday into the weekend as onshore flow
weakens quite a bit and a short-lived pop up ridge moves into the
area on Saturday. We`ll likely see some light to locally moderate
northerly winds across the interior mountains, and northeast
winds across the Santa Lucias. This combo should dramatically
reduce the coverage and extent of the marine layer cloud coverage
each night through morning starting Friday morning. Otherwise
mostly clear skies are expected Friday and much of Saturday.

.LONG TERM (SUN-WED)...16/1228 PM.

Quiet weather continues Sunday and most likely through the
extended period. A weak upper level low will swing into the area
Sunday, most likely remaining overhead through Monday and
potentially Tuesday. While the most likely outcome is generally
slightly cooler temps with a deeper and more expansive marine
layer and the potential for morning drizzle, there is a very small
chance for isolated shower or thunderstorm activity (likely
focused over the interior mountains). Most European ensemble
members show increasing PWATs as the upper low`s cyclonic flow
attempts to pull in some moisture from the fetch to our south and
east, but PWAT values are not very substantial with a mean just
over 1". Additionally most members also show some increasing CAPE
over the area. However QPF output is very limited to nil, so it
appears that the still limited moisture and the weakness of the
trough will limit any sort of convective initiation. We will
continue to monitor this very low chance for some "exciting"
weather in an otherwise quiet pattern.

For Tuesday-Wednesday the most likely outcome is for that upper
low to be replaced by weak ridging with slightly increasing 500
mb heights and weakening onshore flow, resulting in region-wide
warming. There does remain a very low chance for that mountain
focused convective activity continues.

&&

.AVIATION...17/0553Z.

At 0508Z at KLAX, the marine layer was 3300 feet deep. The top of
the inversion was at 6500 feet with a temperature of 17 C.

High confidence in TAFs for KPMD and KWJF.

Moderate in remaining TAFs. Cigs may vary between 025 and 035.
Low VFR cigs may not scatter out until 18/00Z.

KLAX...Moderate confidence in TAF. Cigs may vary between 025 and
035 through 20Z. BKN035 conds may persist through 00Z. There is a
15% chance of an east wind component of 6-8 kts 09Z-16Z.

KBUR...Moderate confidence in TAF. Cigs may vary between 025 and
035 through 20Z. BKN035 conds may persist through 00Z.

&&

.MARINE...16/910 PM.

For the outer waters, moderate to high confidence in the current
forecast. Winds and seas will remain below Small Craft Advisory
(SCA) levels through this afternoon. Winds are likely to increase
to SCA levels tonight and continue through Monday night, most
prevalent and long-lasting for the waters west and south of Point
Conception. Expect steep, choppy seas with the SCA conditions.

For the inner waters N of Point Sal, generally high confidence in
the current forecast. Conds are expected to be below SCA levels
through Friday morning, then SCA wind gusts are likely during the
afternoons and evenings from Friday through Sunday.

For the inner waters S of Point Conception, moderate confidence
in the current forecast. Conds are expected to be below SCA levels
for the most part through Monday night. However, for the western
Santa Barbara Channel, there is a 60% chance of SCA wind gusts
Friday evening, a 50% chance of these gusts Monday evening, and a
30% chance of these gusts Saturday evening and Sunday evening.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM Thursday to 3 AM PDT
      Saturday for zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Lewis/KL
AVIATION...Rorke
MARINE...Sirard/Ciliberti
SYNOPSIS...Lewis

weather.gov/losangeles

Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox