Signal Hill, California Weather Forecast Discussion

849
FXUS66 KLOX 120540
AFDLOX
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1040 PM PDT Thu Sep 11 2025
UPDATED AVIATION SECTION
.SYNOPSIS...11/746 PM.
A period of cooler, well below normal temperatures will last at
least through the weekend. Morning marine layer clouds will
cover many coastal and valley areas through Friday, followed by a
gradual warming trend for the weekend and continuing into next
week.
&&
.SHORT TERM (THU-SUN)...11/812 PM.
***UPDATE***
The main forecast issues for the overnight period will be gusty
Sundowner Winds, near to just above Advisory level, and overnight
low clouds and fog. In addition, a cold upper low over the region
will bring continued below-normal temperatures to Southwest
California through the short term.
A northerly surface pressure gradient (forecast to increase to -2.7
mb from Santa Barbara to Santa Maria) is causing the northwest
winds over southwest Santa Barbara county. Currently wind gusts in
the area are up to 40 mph with moderate confidence that gusts will
increase to 45 mph in the next few hours. Weaker Sundowner winds
are expected for the next several nights.
The center of a cold upper low is currently over the Oregon/Nevada
border, with a trough extending southward toward Point Conception.
Unseasonably low heights aloft, combined with good onshore flow
and an eddy forming over the San Pedro Channel should provide
another night of fairly widespread low clouds. The best coverage
will be over the Central Coast, Santa Ynez and Salinas Valleys,
and LA County coast, coastal valleys and Santa Monicas. The Santa
Barbara South Coast is expected to remain clear due to the
northerly winds, while the Oxnard Plain may see patchy low clouds
near the beaches.
Finally, high temperatures tomorrow are expected to increase 3 to
6 degrees away from the coast, as a weak ridge moving over there
initiates a gradual warming trend.
***From Previous Discussion***
An unseasonably cold upper level low over eastern Oregon and Idaho
is starting to slowly move east and behind that a weak ridge will
move over the West coast. This will bring about a slow warming
trend this for inland areas this weekend, though temperatures
will still be 2-5 degrees below normal on Sunday. For coastal
areas, temperatures will change very little as the warm SST`s have
created a warm bias there of 2-4 degrees lately, especially south
of Pt Conception. The strong winds there the last few days should
theoretically create some upwelling that will cool the coast down
to normal but low confidence in that. The deep marine layer
currently is expected to shrink over the weekend with the ridge,
eventually confining any stratus to the coastal areas, but that
may not happen til Sat or Sun.
.LONG TERM (MON-THU)...11/1130 AM.
Another weak trough will move through the PacNW early next week
but models have been trending weaker and farther north with it so
impacts to SoCal are expected to be minimal and the previous slow
warming trend should still continue.
By Tue and especially Wednesday there is increasing consensus in
the ensemble solutions that the next heat wave will begin. At the
same time though models are also indicating a return of monsoon
moisture as the next tropical wave moves off northern Mexico. PW`s
are expected to rise to at least 1.5" by mid week, with roughly
10% of solutions showing PW`s as high as 2" by Thursday and Friday
(highest south of Pt Conception). The added moisture complicates
the temperature forecast, but absent that we could be looking at
warmer valley highs reaching 105-110 (roughly a 20-30% chance by
next Wednesday) and inland coastal areas in the low to mid 90s.
Overnight temperatures will be warming up as well, especially as
moisture increases aloft and hinders the usual overnight cooling.
Both high and low temperature forecasts next week have been
adjusted upward over the NBM. Depending on the trajectory and
timing of the moisture arrival, the hottest day will likely be
Wednesday, with some cooling Thu/Fri but with increasing
humidities and likely cloud cover. This looks like a favorable
setup for showers and possible thunderstorms across the area
(including coast and valleys) later in the week.
&&
.AVIATION...12/0539Z.
At 0427Z at KLAX, the marine layer depth was 1300 ft, with an
inversion topped at 1900 feet and 19 degrees C.
High confidence in TAFs for KPMD and KWJF.
Low confidence in all coastal and valley TAFs due to a patchy
marine layer with a weak inversion. Cigs may frequently bounce
between BKN and SCT IFR-MVFR through 18Z at any coastal or valley
site. There is a chance for no low clouds at KSBP (30%), KSMX
(20%), KSMO (40%), KLAX (40%), and KLGB (40%). There is a chance
for low clouds to form at KOXR (25%), KCMA (15%), KBUR (25%), and
KVNY (25%) between 10Z and 18Z. Minimum flight cat may be off +/-
1 cat. Higher confidence in a more widespread marine layer after
00Z Sat, but arrival times may be off +/- 3 hours.
KLAX...Low confidence in TAF. Cigs tonight may form as early as
08Z and as late as 14Z and are likely to bounce between BKN and
SCT 010-025. There is a 20 percent chance of an east wind
component of 8 kt from 10Z-17Z Fri. Higher confidence in BKN08-015
cigs after 02Z Sat, but arrival times may be off +/- 3 hours.
KBUR...Low confidence in TAF. There is a 25% chance of
BKN010-BKN025 cigs 10Z-18Z Fri. Cigs may frequently bounce from
BKN to SCT.
&&
.MARINE...11/812 PM.
Small Craft Advisory (SCA) level NW winds (peaking at 20-30 kts)
will impact the outer waters through Monday night. Winds will be
the strongest during the afternoons and evenings, and lulls may
occur during the morning hours. The nearshore waters along the
Central Coast will see SCA level NW winds (20-30 kts) each
afternoon and evening through Monday night. Seas will peak around
6 to 8 feet beginning this afternoon through Monday.
For the inner waters south of Point Conception, SCA level WNW
winds (20-25 kts) are likely across the Santa Barbara Channel Friday.
Seas will peak at 4 to 6 feet each afternoon and evening Friday,
and seas will be short period and choppy. Chances for SCA winds
are lower over the weekend as winds trend slightly weaker and more
NW. Some localized NW gusts to 20 kts may occur near Point Dume
and west of Catalina Friday afternoon and evening, then winds
will trend lighter over the weekend.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory remains in effect until 5 AM PDT Friday for
      zones 349-351. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until midnight PDT tonight for
      zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Friday for
      zones 650-670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Saturday for
      zones 673-676. (See LAXMWWLOX).
&&
$$
PUBLIC...MW/Ciliberti
AVIATION...Lewis
MARINE...Phillips/Schoenfeld
SYNOPSIS...MW/Schoenfeld/Ciliberti
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox

NWS LOX Office Area Forecast Discussion