Mount Baldy, California Weather Forecast Discussion

979
FXUS66 KLOX 080355
AFDLOX
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
855 PM PDT Sun Sep 7 2025
.SYNOPSIS...07/752 PM.
A significant cooling trend will begin Monday as a low pressure
system approaches northern California. This will result in much
cooler temperatures across Southwest California by Wednesday and
Thursday. In addition, marine layer clouds will expand across
coastal areas and well inland over the valleys. A warming trend
is then expected Friday into the weekend.
&&
.SHORT TERM (SUN-WED)...07/853 PM.
***UPDATE***
Temperatures were fairly close to normal today, with much warmer
values for most west-facing coasts where offshore morning
gradients lead to about 5 to 10 degrees of warming. As the low
pressure system off the coast of northern California approaches,
we should start to see a widespread cooling trend along with a
deepening marine layer and more coastal clouds and fog. However,
lower confidence in how exactly the marine layer will be affected
tonight, given heights remain around 590 DAM overnight. Will
likely see more significant deepening Monday night and through the
week. Some sundowner winds have developed tonight, but will
likely remain below advisory levels whereas tomorrow night still
looks on track for advisory level sundowner winds. Current
forecast looks on track, and temperatures were cooled 2-4 degrees
given the approaching low.
***From Previous Discussion***
Today was the last day of warming before the significant cooling
trend starts up on Monday. This cooling will be a result of a low
pressure system moving toward northern California, with an
associated trough extended southward over SW CA. Most areas will
experience 2-5 degrees of cooling Monday, then another 3-6 degrees
of cooling Tuesday resulting in highs 5-10 degrees below normal
in all areas except the immediate coast. Highs across the
immediate coast will remain just slightly below normal during
Monday and Tuesday.
As the trough moves toward the region, 500mb heights will drop,
and cause rapid deepening of the marine layer, with clouds likely
pushing into the valleys by Tuesday morning if not before. With
the cooling aloft causing ascending air in the boundary layer with
the deepening marine layer, there is a possibility of some
morning drizzle Monday and Tuesday across the coast and valleys,
mainly south of Pt Conception. Depending on how quickly the
marine layer deepens it`s also possible some coastal areas will
remain cloudy all day.
As the trough moves onshore later Monday, increasing northerly
flow will generate some gusty Sundowner winds across southwest
Santa Barbara County Monday evening with gusts to 45 mph. With
increasing onshore flow to the east, there will be some gusty
southwest winds, especially on Tuesday, across the Antelope
Valley/adjacent foothills, and especially the eastern San Gabriel
Mountains (where gusts up to 50 mph will be possible in the mtns).
.LONG TERM (THU-SUN)...07/238 PM.
The upper low will basically take up camp along the West Coast
all week, maintaining much below normal temperatures, especially
inland where highs will be as much as 10-15 degrees below normal
Wednesday through at least Friday. 500mb heights will drop below
580dam, the lowest it has been since June. The marine layer will
likely be at least 3000 feet deep with very slow clearing,
especially near the coast. There will be drizzle chances each
night and morning through Friday, especially LA/Ventura Counties.
However, the best chances for drizzle will be on Wednesday and
Thursday, as upper level vorticity combines with the deepening
marine layer and cooling temperatures aloft, mainly Wednesday
night into Thursday morning.
Most of the ensemble solutions support a slow warming trend next
week but temperatures will remain at least 3-6 degrees below
normal.
&&
.AVIATION...08/0308Z.
At 2300Z at KLAX, the marine layer was 400 feet deep. The top of
the inversion was at 1900 feet with a temperature of 27 C.
High confidence in VFR TAFs for desert airfields (KPMD & KWJF).
High confidence in VFR TAFs for San Fernando Valley airfields.
-> (KVNY & KBUR).
Moderate confidence in remaining TAFs. Timing of CIG/VSBY
restrictions may be off by 2 hours. Lower confidence in clearing
times, which could be up to 2 hours earlier or later than
forecast.
KLAX...Moderate confidence in 00Z TAF. Arrival and departure of
CIGs may be off by 2 hours, and flight categories could be off by
one cat when CIGs are present. Heights likely in range 003-007. No
significant east wind component expected.
KBUR...High confidence in 00Z TAF.
&&
.MARINE...07/813 PM.
This coming week, high confidence in SCA level winds during the
afternoon & evening hours south of Point Conception, with a 20%
chance of GALE force wind gusts Monday night, Tuesday afternoon
and Tuesday night. Marginal SCA level wind gusts each
afternoon/eve will be possible north of Point Conception through
Wednesday, with increasing chances through next weekend. Seas are
likely to remain at or below 8 feet through Friday.
For the nearshore waters north of Point Sal, SCA gusts will be
possible each afternoon/evening period Monday through Friday. The
highest chances (40-50%) will be on Wednesday and Thursday.
Inside the southern California bight, SCA level winds will be
widespread across the Santa Barbara Channel, with a moderate
chance of reaching the Ventura Coastline & Santa Monica Bay
Monday afternoon/evening & even more likely on Tuesday. Wind
gusts may reach 30 kt across the SBA Channel, with a 10% chance
(Monday) & a 20% chance (Tuesday) of GALE force wind gusts.
Also, seas may exceed 5 feet across western/southern portions of
the SBA Channel on Monday & Tuesday. Wind gusts greater or equal
to 21 kts is possible across the San Pedro Channel, near Point
Dume, and the western portion of PZZ655 each afternoon/eve over
the next several days.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 1 PM Monday to 5 AM PDT
      Tuesday for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zones 673-676. (See LAXMWWLOX).
&&
$$
PUBLIC...Phillips/Lund
AVIATION...Phillips/Black
MARINE...Black/Ciliberti
SYNOPSIS...MW/CC
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox

NWS LOX Office Area Forecast Discussion