Diamond Bar, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

806
FXUS66 KLOX 201140
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
440 AM PDT Fri Jun 20 2025

Updated Aviation Section

.SYNOPSIS...20/219 AM.

A cooling trend will continue through Saturday as low pressure
develops along the West Coast, along with increasing night
through morning low clouds and fog. Gusty northerly winds are
expected across southern Santa Barbara County, through the
Interstate 5 Corridor and for other interior areas for the next
several nights. A warming trend for inland areas is expected to
begin Sunday but below normal temperatures are expected to
continue into next week.

&&

.SHORT TERM (TDY-SUN)...20/306 AM.

Main focus through Saturday remains the winds across southern
Santa Barbara County, but gusty winds also expected in other parts
of the mountains and interior areas. Winds gusted to just under
60 mph last evening and even stronger winds are expected Friday
night which should be the peak of this latest stretch of
Sundowners. Latest hi res model guidance shows widespread gusts of
40-55 mph across the front country and Santa Ynez Range as far
east and Refugio Friday evening, but still gusty through Goleta
and the city of Santa Barbara as well. Models show decreasing
northerly gradients Saturday but increasing winds aloft,
particularly from 850-700mb. This could impact some of the higher
portions of the Transverse range. Gusty winds are also expected
across the I5 corridor region and the Antelope Valley the next
couple days.

Outside of those areas, no significant weather issues the next
several days. The cooling trend that began Thursday for areas away
from the immediate coast will continue through Saturday as a
trough deepens along the West Coast. Coastal areas won`t notice
much difference but inland areas will be around 3 degrees cooler
Friday and 4-8 degrees cooler Saturday. The marine layer will
deepen with the cooling aloft and forecast soundings show it could
be around 2500 feet by Saturday in the LA Basin. However, latest hi
res models are indicating stratus coverage may remain mostly just
over LA County, possibly a response to the strong northerly winds
to the west.

A warming trend is expected Sunday, again mainly just for inland
areas as onshore flow and winds aloft weaken, allowing warmer air
from southeast CA to shift west. Highs expected to rise 5-10
degrees most inland areas, but at most just 1-3 degrees of warming
near the coast. Despite the warm up, temperatures will still be
3-6 degrees below normal.

.LONG TERM (MON-THU)...20/301 AM.

After the big jump in temperatures Sunday, just very minor day to
day adjustments through mid week. Models are not indicating any
significant winds other than the typical afternoon/evening winds
for the AV. Highs expected to remain a few degrees below normal.
With decreasing winds aloft and less mixing and still moderate to
strong onshore flow it`s likely the marine layer coverage will
increase rapidly and spread into more of the the coastal valleys
as well.

&&

.AVIATION...20/1139Z.

At 11Z over KLAX, the marine layer was 1600 feet deep with an
inversion top at 4200 feet with a temperature of 23 Celsius.

Moderate confidence in flight category forecast and timing.

At KSBA, high chance of either LLWS 20-30 knots Friday night or
north gusts surfacing 20-30 knots.

Reduced vis from BLDU possible 21-06Z at KSMX KPMD KWJF. KWJF has
highest risk, with a low but present chance of LIFR/IFR.

KLAX...Moderate confidence in bases staying in the 010-020 range.
Clearing to VFR could happen as early as 16Z or as late as 20Z.
Southeast winds likely after 12Z, with a 20% chance of exceeding 8
knots.

KBUR...Moderate confidence in bases at 006-012. Clearing to VFR
could happen as early as 15Z or as late as 17Z. High confidence in
slightly stronger than normal onshore winds in the afternoon.

&&

.MARINE...20/237 AM.

***HAZARDOUS SEAS THROUGH SATURDAY***

High confidence in prolonged Gale Force northwest winds beyond 20
miles from shore through Saturday night, strongest this afternoon
through Saturday evening. Moderate confidence in gusts of 30 to
35 knots impacting the nearshore Central Coast waters and western
Santa Barbara Channel each afternoon and evening during this
stretch. All waters will see building and hazardously steep short
period seas. While winds will likely not reach Small Craft
Advisory (SCA) everywhere, decided to issue a SCA for all areas
not in the Gale due the combination of widespread steep seas and
the potential for widespread gusts. Small craft should stay in
safe harbor, especially in the afternoon and evening hours.

High confidence in lowering winds and subsiding seas for the first
half of next week, with abnormally large high tides each evening.
SCA winds are still likely for the waters beyond 20 miles for
shore, which is typical for this time of the year.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory remains in effect until 9 PM PDT this evening
      for zones 340-341-346-347. (See LAXNPWLOX).
     Wind Advisory remains in effect until 3 AM PDT Saturday for
      zones 342-343-378-379-381>383. (See LAXNPWLOX).
     Wind Advisory now in effect until 4 PM PDT this afternoon for
      zones 349-351. (See LAXNPWLOX).
     High Wind Watch in effect from 4 PM PDT this afternoon
      through late tonight for zones 349-351. (See LAXNPWLOX).
     Wind Advisory in effect from 4 PM this afternoon to 3 AM PDT
      Saturday for zones 350-352. (See LAXNPWLOX).
PZ...Gale Warning in effect from 2 PM this afternoon to 3 AM PDT
      Saturday for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect from 2 PM this afternoon to 6
      PM PDT this evening for zone 650. (See LAXMWWLOX).
     Gale Warning in effect from 6 PM this evening to 3 AM PDT
      Saturday for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect from 2 PM this afternoon to 3
      AM PDT Saturday for zone 655. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Sunday for zones
      670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW
AVIATION...Kittell
MARINE...RK
SYNOPSIS...MW/Sirard/Ciliberti

weather.gov/losangeles

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