Simi Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

498
FXUS66 KLOX 201003
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
303 AM PDT Fri Mar 20 2026

.SYNOPSIS...20/222 AM.

Temperatures will remain well above normal through next week,
though some cooling is expected today and through this weekend.
Areas of dense coastal fog will be possible through the weekend as
well. Temperatures will trend upward again next week but are not
expected to be as hot as this week.

&&

.SHORT TERM (TDY-SUN)...20/243 AM.

One last day of extreme heat before some weekend cooling brings
some relief. A 595 dam upper high straddling the CA/AZ border
will bring 592 dam hgts and 580 dam thkns to the area today. Both
of these value have never been seen in March before this extreme
heat event. There will be weak offshore flow this morning and then
weak onshore flow in the afternoon as the pressure gradients
follow a standard diurnal cycle. Skies will be sunny today, save
for a chance of morning low clouds in the Long Beach/Torrance
area. The seabreeze will bring 1 or 2 degrees of cooling to the
csts and vlys today, but nowhere near enough to eliminate the
extreme heat and heat warnings and advisories cover the forecast
area with max temps remaining 18 to 28 degrees above normal.

A more robust marine layer cloud pattern will develop tonight as
onshore flow increases and a weak eddy spins up. The marine layer
will be smooshed so low that anywhere low clouds form they will be
accompanied by dense fog. The stronger onshore push and the
cooling marine layer will combine to bring 4 to 8 locally 10
degrees of cooling to almost all of the area. Max temps will end
up "only" 10 to 20 degrees above normal with the warmest vlys
seeing highs in the lower 90s. Even though these temperatures are
well above normal they do not pose a significant heat threat and
no advisories or warnings will be needed.

The ridge finally breaks down on Sunday as some energy comes in
from the west. Hgts fall to 582 dam. Offshore flow redevelops from
the north and this will reduce the amount of low clouds. The
lowering hgts will raise the marine layer and eliminate the threat
of dense fog. Most of the area will cool a degree or two but some
areas susceptible to north winds will see a few degrees of
warming.

.LONG TERM (MON-THU)...20/300 AM.

The east PAC upper high reasserts itself Monday and persisted
into Wednesday before braking down on Thursday. Hgts will mostly
be around 588 dam through Wed. The good news is that there will
continuous onshore flow from the west through the period. There
will be some offshore flow from the north in the mornings but the
east push will help limit the warming, esp near the coast. Mdls do
keep the marine layer clouds away through the period but would
not be surprised if there were ocnl bouts of morning stratus and
dense fog. Look for 2 to 3 degrees of warming Monday and 1 to 2
additional degrees on Tuesday. Max temps will then change little
on Wednesday. Max temps will be 15 to 22 degrees above normal and
there may be a need for heat advisories for some of the csts and
vlys. During this time max temps will mostly be in the 80s across
the csts and in the 90s in the vlys.

There will be some, but not much cooling on Thursday.

Both AI mdls do not show any chc of rain through the end of the
month. Both mdls do, however, show rain at the beginning of the
month - esp the GFS-AI.

&&

.AVIATION...20/1003Z.

At 0818Z at KLAX, the marine layer was 400 ft deep. The top of
the inversion was at 1600 ft with a temperature of 29 C.

High confidence in all TAFs, except for KSMO, KLAX, & KLGB with a
30 to 40 percent chc of LIFR cig/vis 12Z-17Z.

Lesser confidence tonight with respect to low clouds with LIFR
conds arrival timing.

KLAX...Low confidence in TAF. There is a 40 percent chc of 1SM
OVC003 conds 12Z-17Z. LIFR conds could arrive as early as 06Z
this evening. Good confidence that any east wind component will
be under 6 kt.

KBUR...High confidence in VFR TAF.

&&

.MARINE...19/707 PM.

Conditions are likely to remain below Small Craft Advisory (SCA)
levels through Friday night or Saturday morning. SCA conditions
are likely to develop Saturday afternoon through Sunday across the
outer waters and the nearshore waters along the Central Coast.
Seas will reach 8-12 feet, and there is a low (20-30 percent)
chance of GALE FORCE winds, highest from around Point Arguello
south to the Channel Islands Saturday night and Sunday. Winds are
expected to gradually subside Sunday night through Monday.

Areas of dense fog are likely to be widespread tonight into
Friday morning.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory remains in effect until 8 PM PDT this evening
      for zones
      38-87-340-341-343-344-346>350-354-355-362-366-367-549-550. (See LAXNPWLOX).
     Heat Advisory in effect until 8 PM PDT this evening for zones
      38-87-343-344. (See LAXNPWLOX).
     Extreme Heat Warning in effect until 8 PM PDT this evening
      for zones 88-342-345-351>353-356>358-368>376-378>380-548. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 2 PM Saturday to 3 AM PDT
      Sunday for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect from 2 PM Saturday to 3 AM PDT
      Monday for zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect from 5 PM Saturday to 3 AM PDT
      Monday for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke
AVIATION...Rorke
MARINE...Schoenfeld/Ciliberti
SYNOPSIS...MW/CC

weather.gov/losangeles

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