Irwindale, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

375
FXUS66 KLOX 292117
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
217 PM PDT Sun Jun 29 2025

.SYNOPSIS...29/216 PM.

Expect dry conditions and generally near-normal temperatures for
this week and next weekend, with night through morning low clouds
and patchy fog over the coasts and coastal valleys. In the extended
outlook, starting July 7th of the following week, there will be
the potential for a heatwave to build over the region accompanied
by triple-digit heat across portions of the interior, along with
the first influx of monsoonal moisture of this summer bringing a
small chance for thunderstorms over the mountains and deserts.
Please monitor the latest information from the National Weather
Service in Los Angeles/Oxnard over the coming days, as forecast
details are refined.

&&

.SHORT TERM (TDY-WED)...29/216 PM.

Little overall change in sensible weather conditions is expected
through the week. It will remain dry through the period, and
quiescent weather conditions will prevail. As the trough-ridge
pattern across the Pacific coast sharpens in response to an
approaching/deepening upper low offshore and a building/
amplifying downstream ridge over the Great Basin and Rockies,
onshore pressure gradients will increase for early parts of this
week. Afternoon LAX-DAG gradients are forecast to peak around
7.5-8.5 mb each afternoon, bringing an uptick in onshore flow.
Resultant breezy southwest to west winds will gust upwards of
30-45 mph over the mountains and deserts each afternoon and early
evening, though the probability of Wind Advisories is currently
below 20 percent.

With the boost in onshore flow, a stronger influx of the marine
layer will spread low clouds and patchy fog farther inland each
night and morning. However, while the upper low stalls offshore
through early in the week, the downstream upper ridging will
offset significant deepening of the marine layer through Monday,
with marine stratus and patchy fog likely dissipating in most
areas by afternoon.

However, by Monday night and Tuesday, the upper low will begin to
slowly edge eastward toward and across the local area. Accompanying
cyclonic vorticity advection and related differential advection
preceding the upper low will overwhelm height fields over the
local area to facilitate more pronounced deepening and inland
spread of the marine layer. Marine clouds and fog should be slower
to clear over coastal areas and the coastal valleys on Tuesday,
and will likely extend farther inland across most of the coastal
valleys by early Tuesday morning before more slowly dissipating.
While unlikely, a few patches of light drizzle could be mixed in
with the deeper marine layer Monday night and/or Tuesday morning,
especially if a mesoscale eddy were to focus onshore flow
somewhere between Santa Monica and Long Beach, and also along the
Central Coast. Otherwise, dry conditions are expected areawide
through next week. The cold pool aloft attendant to the upper low
may erode the inversion surmounting the marine layer on Wednesday,
muting stratus/fog development and/or fostering early-day onset
of its dissipation.

Another overall effect from the strengthening onshore flow will be
a very gradual cooling trend, which will pick up some by the
middle of next week as the cold pool aloft moves over the local
area. High temperatures will be in the 80s and 90s in most places
away from the coast through Tuesday, with 60s and 70s at the
beaches. However, cooling by a couple degrees is expected at most
locations from day to day. The significant downstream ridging will
be a primary factor in precluding more substantial cooling that
would otherwise be facilitated by the uptick in onshore flow. By
Wednesday, with the cold pool aloft overhead, high temperatures
expected to remain below 90 degrees in most areas except for the
Antelope Valley.

.LONG TERM (THU-SUN)...29/216 PM.

Midlevel heights are forecast to rebound by the end of this week,
which should correspond to gradual reinforcement of the marine
layer, along with accompanying night through morning low clouds
and fog near the coast. A very slow warming trend is anticipated
mainly for locations away from the coast by Friday and continuing
into next weekend. However, reinforcing upper vorticity centers
north of the forecast area should have the peripheral effect of
limiting midlevel height rises. This will tend to mute the
magnitude of warming from day to day.

Breezy winds with local gusts of 30-45 mph will persist over the
mountains and deserts in the enhanced onshore flow, facilitated by
the moderate pressure gradients. While a few gusts could exceed
45 mph, confidence in any more than brief/spotty advisory-level
gusts is low, and the probability for wind headlines to be issued
is currently under 20 percent.

In summary, little overall change in sensible weather conditions
is expected through next weekend across the area. It will remain
dry through the period, and quiescent weather conditions should
prevail through the entirety of the forecast period.

However, starting July 7th of the following week, a large subset
of numerical model solutions depict a pattern shift, with the
guidance envelope pointing toward significant strengthening of an
upper ridge between the Four Corners region and the Rockies. These
solutions suggest an upper ridge axis extending west-southwestward
to the local area, which indicates the potential for a heatwave
to build over the region accompanied by triple-digit heat across
portions of the interior. Moreover, this pattern has the potential
to feature the first influx of monsoonal moisture of the summer
bringing a small chance for thunderstorms over the mountains and
deserts -- less than 10 percent chance at the present time.
Ultimately, there are many synoptic and mesoscale details during
this distant-extended time range that will have significant
bearing on local forecasts and still have yet to come into better
focus during the next several days. Overall, numerical models are
offering stronger consensus depicting the large-scale pattern
than they usually would for this distant of a time range --
offering higher-than-average confidence in more significant
weather impacting the region during the following week starting
July 7th. Please stay tuned.

&&

.AVIATION...29/1614Z.

At 1600Z at KLAX, the marine layer was 1000 ft deep. The top of
the inversion was at 2700 ft with a temperature of 24 C.

For 18Z TAF package, high confidence in KBUR, KVNY, KPRB, KWJF and
KPMD.

For coastal sites, moderate confidence in 18Z TAF package. Timing
of flight category changes tonight could be +/- 2 of current
forecasts and flight category minimums could be off by one
category.

KLAX...Overall, moderate confidence in 18Z TAF. For tonight,
timing of return of CIG/VSBY restrictions could be +/- 2 hours of
current 04Z forecast and dissipation Monday morning could be +/-
2 hours of current 17Z forecast. No significant easterly wind
component is expected.

KBUR...High confidence in 18Z TAF. There is a 10-15% chance of
LIFR conditions 10Z-16Z.

&&

.MARINE...29/1135 AM.

For the Outer Waters, moderate to high confidence in current
forecast. Through Tuesday, high confidence in winds and seas
remaining below Small Craft Advisory (SCA) levels and much
quieter than usual. On Wednesday, there is a 20-30% chance of SCA
level winds. For Thursday through Friday, there is 30-50% chance
of SCA level winds and seas.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Through Wednesday, winds and seas
will remain below SCA levels and remain much quieter than usual.
For Thursday through Friday, there is a 30% chance of SCA level
winds, mainly in the afternoon and evening hours.

For the Inner Waters south of Point Conception, high confidence in
current forecast. Today through Friday, winds and seas are
expected to remain below SCA levels.

Patchy dense fog will impact the coastal waters, especially north
of Point Conception through Monday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...Cohen
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Cohen

weather.gov/losangeles

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