Montrose, California Weather Forecast Discussion

891
FXUS66 KLOX 091644
AFDLOX
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
944 AM PDT Tue Sep 9 2025
.SYNOPSIS...08/724 PM.
A significant cooling trend will continue through Thursday as a
low pressure system approaches northern California. This will
result in much cooler temperatures across Southwest California.
In addition, marine layer clouds will expand across coastal areas
and well inland over the valleys with morning drizzle possible
through Friday. A small warming trend is then expected Friday into
the weekend.
&&
.SHORT TERM (TDY-THU)...09/942 AM.
***UPDATE***
Cloud coverage was extensive this morning, and spilled into many
coasts and valleys. A weak Catalina Eddy will keep clouds across
the LA Basin late into this morning. Strong upper level west-
southwest winds will drive gusty onshore winds across the San
Gabriel Mountains and the Antelope Valley Foothills. Additionally
northwest Sundowner Winds are anticipated to restrengthen late
this afternoon through tonight across southwestern Santa Barbara
County. Breezy conditions may extend as far east as the foothills
above Goleta. A Wind Advisory has been added for SW Santa Barbara
County tonight, in addition to today`s advisory for the San
Gabriel Mountains and Antelope Valley Foothills.
There is a less than 10 percent chance of an afternoon shower and
a non-zero chance of lightning across the interior mountains
tomorrow and Thursday afternoon, as a result of vorticity and
periphery moisture brought by the trough.
***From Previous Discussion***
A large and unseasonably cool (569 dam) upper low will move into
NRN CA today and will persist over the area through early Thursday
before slowly pushing to the east. The upper low will bring
increasing cyclonic flow and lowering hgts to Srn CA. Hgts this
morning are near 586 dam and will fall to 578 dam by Thursday.
Moderate onshore flow to the east will continue through the
period. In the N/S direction there will be weak offshore flow in
the morning and moderate onshore flow in the afternoon.
The increasing cyclonic flow tonight will bring a hefty amount of
lift and low clouds should penetrate deep into the vlys. The lift
will be strong enough to bring areas of drizzle to much of the
coasts and vlys as well. The low cloud pattern will be similar on
Thursday morning, but there will be much less lift and the threat
of drizzle will be much reduced.
The deeper marine layer and lowering hgts will combine to bring
two days of cooling to almost all areas. Look for 3 to 6 locally 8
degrees of cooling today and then an additional 2 to 4 degrees on
Wednesday. There will be slightly less cooling across the near
shore area. Thursday`s temps will change little from Wednesday`s
values. Max temps across the vlys on Wed/Thu will be 6 to 12
degrees blo normal.
The gusty winds aloft assoc with the trof and a moderate onshore
push to the east will bring low end advisory level wind gusts to
interior passes and canyons of the San Gabriel Mountains and the
Antelope Valley Foothills through this evening.
.LONG TERM (FRI-MON)...09/303 AM.
The trof will continue to slide to the east on Friday and will be
replaced by a weak ridge which will raise hgts to about 585 dam
and persist into Saturday. The increase in hgts will smoosh the
marine layer some and this will limit the vly penetration south of
Pt Conception. Weak offshore flow across the Santa Ynez range will
also keep most of the SBA south coast clear as well. Moderate
onshore flow into the Central Coast will keep a robust stratus
layer across the area as well as the Santa Ynez Vly. The ridge as
well as a faster clearing marine cloud layer will allow for 2 to 3
degrees of warming each day. Despite this warming max temps will
remain 3 to 6 degrees blo normal across the coasts and 5 to 10
degrees across the vlys.
The ridge is short lived and will be replaced by a weak trof for
Sun and Mon. Hgts and pressure gradients really do not change much
at all and there will actually not be much change in the night
through morning cloud pattern or the temperatures.
&&
.AVIATION...09/1018Z.
Around 0430Z at KLAX, the marine layer depth was around 800 feet
deep. The top of the marine inversion was near 1800 feet with a
temperature around 23 degrees Celsius.
High confidence exists in the current forecast for desert
terminals. Low-to-moderate confidence exists in the current
forecast for coastal and valley terminals.
IFR to MVFR conditions will develop at most coastal and valley
terminals through 15Z. There is a low-to-moderate chance of VFR
conditions persisting at Los Angeles County coastal and valley
terminals through tonight. There is a small chance of IFR
conditions in drizzle or light rain through 17Z. There is a better
chance of low clouds with IFR to MVFR conditions tonight at
terminals south of Point Conception.
KLAX...IFR to MVFR conditions could spread into KLAX as soon as
12Z. There is a 10 percent chance of VFR conditions persisting
through at least 06Z Wednesday. VFR conditions should develop by
18Z at the latest. A return of IFR to MVFR conditions could occur
as soon as 01Z Wednesday or as late as 08Z Wednesday. There is a
30 percent chance of IFR conditions in drizzle this morning and
after 08Z Wednesday. There is a 30 percent chance of east winds
between 7 and 10 knots between 14Z and 17Z.
KBUR...There is a 40 percent of no low clouds at KBUR. VFR
conditions should develop by 16Z at the latest. IFR to MVFR
conditions could arrive as soon as 05Z or as late as 10Z.
&&
.MARINE...09/831 AM.
Across the outer waters south of Point Sal, Small Craft Advisory
(SCA) northwest winds are expected through at least Sunday, with
brief lulls possible during the morning hours. North of Point Sal
(including the nearshore waters), there is a 30% chance of SCA
winds during the afternoon/evening hours today and Wednesday,
increasing to a 40-50% chance Thursday afternoon and continuing
through Saturday (with lulls during the morning hours). Wind
driven, short period, choppy seas will be likely during the
afternoon/evening hours accompanying the winds, and heights will
peak at around 6 to 8 feet Thursday afternoon through the weekend.
For the inner waters South of Point Conception, SCA level west
winds are likely during the afternoon/evening hours through
Wednesday night, especially across the Santa Barbara Channel,
near Point Dume, and across the San Pedro Channel. Chances for SCA
level winds decrease to 40-50% for the afternoon/evening hours
Thursday through the weekend. Wind driven, short period, choppy
seas are likely during the afternoon/evening hours accompanying
the winds and heights will peak Wednesday night at around 3 to 6
feet.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect from 5 PM this afternoon to 5 AM PDT
      Wednesday for zones 349-351. (See LAXNPWLOX).
     Wind Advisory remains in effect until 9 PM PDT this evening
      for zones 379>382. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday for
      zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 9
      PM PDT this evening for zone 655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Thursday for
      zones 673-676. (See LAXMWWLOX).
&&
$$
PUBLIC...Rorke/Schoenfeld
AVIATION...Hall
MARINE...Lund
SYNOPSIS...CC/KL
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox

NWS LOX Office Area Forecast Discussion