516
FXUS66 KLOX 171651
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
951 AM PDT Thu Jul 17 2025

.SYNOPSIS...16/115 PM.

There will be a slight chance of showers and thunderstorms
Thursday into Friday across eastern Los Angeles County.
Otherwise, night through morning low clouds and patchy fog will
continue for the coasts and most valleys through the weekend.
Below normal temperatures are expected into early next week,
though a slow warming trend will develop Thursday and Friday.

&&

.SHORT TERM (TDY-SAT)...17/949 AM.

***UPDATE***

Marine layer clouds are retreating from the coasts and valleys,
with mostly clear skies this morning across LA County. High clouds
are streaming into the region from the east, indicative of the
monsoonal moisture reaching the area.

This afternoon there is a slight chance of showers or
thunderstorms focused over the San Gabriel Mountains. Late tonight
into Friday morning, there is a slight chance of showers or
thunderstorms across all of LA County and much of Ventura County.
Friday afternoon, there is 20-30 percent chance focused over the
Ventura County Mountains, San Gabriel Mountains, and Antelope
Valley, with a slight chance to reach the nearby valleys.

Dry lightning and gusty winds are the most likely hazards if a
storm were to form, with a smaller chance of heavy downpour,
especially over the higher terrain Friday afternoon.

***From Previous Discussion***

The marine layer is much lower (1200 ft vs 3000 ft) compared to
ydy and this along with weaker on shore flow will result in less
low cloud coverage than ydy. The offshore trends will also allow low
clouds to clear a little earlier than they have been. A little bit
of moisture will advect into LA county later this afternoon and
will create a slight chc of TSTM over the eastern San Gabriels.
Max temps will be very similar to Wednesday save for the Paso
Robles area which will see about 8 degrees of warming as the
cooler southerly winds stop and turn northward.

Later this evening and the monsoon moisture influx will accelerate
as an upper low to the south switches the upper level flow to the
SE tapping into a wetter portion of the atmosphere. There is not
that much instability but with CAPE values around 700J/km any
little ripple of PVA rotating around the low could trigger a
TSTM. Although steering flow is very light, chances for any
flooding rains is under 5% as most of the moisture will be above
10000 ft. While the Central Coast will see another round of low
clouds the low cloud fcst south of Pt Conception is less certain
as the monsoon push may disrupt it. For now will keep the low
clouds in the fcst but would not be surprised if there are less
clouds than fcst.

The TSTM threat will continue over the LA county mtns and Antelope
Vly (and to a much lesser degree the San Gabriel Vly) through the
day on Friday. Aside from the morning stratus skies will likely be
partly cloudy over LA and portions of VTA counties. Max temps will
not change much across LA/VTA county, but the SBA south coast will
see some weak north winds which will bring 2 to 5 degrees of
warming. The interiors of SLO and SBA counties will also warm a
few degrees.

The monsoon flow cuts off late Friday night and Saturday will have
quiet weather. Again the marine layer south of Pt Conception may
be disrupted, but still it is more likely than not. Rising hgts
will bring 2 to 3 degrees of warming to most areas. Still, max
temps will come in 2 to 4 locally 6 degrees blo normals.

.LONG TERM (SUN-WED)...17/1214 AM.

A very benign 4 days of weather in the xtnd period. Srn CA will be
under dry SW flow as it is sandwiched between high pressure over
the desert SW and broad troffing over the PAC NW. Mdt to strong
onshore flow will return and this will drive a persistent night
through morning low cloud pattern with slow clearing (and no
clearing at some west facing beaches). While there will be some
gusty afternoon winds in the mtn and Antelope Vly they will be
below advisory levels. Max temps will change little each day and
will be 3 to 6 locally 8 degrees below normal.

&&

.AVIATION...17/1650Z.

At 1630Z at KLAX, the marine layer was 1400 ft deep. The top of
the marine inversion was at 4300 feet with a temperature of 22 C.

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

For other coastal/valley TAFs, moderate confidence in 18Z TAF.
Timing of return of CIG/VSBY restrictions could be +/- 2 hours of
current forecasts. There is a 40% chance that CIG/VSBY
restrictions do not develop tonight from KOXR southward due to
incoming mid-level moisture.

There is a chance of TSTMs this afternoon over the LA county
mountains, with a slight chance of TSTMs tonight/Friday morning
across all of Ventura and LA counties. Gusty downburst winds as
well as lightning will be the main potential hazards.

KLAX...Overall, moderate confidence in 18Z TAF. There is a 40%
chance that CIG/VSBY restrictions do not develop tonight. There is
a 10-15% chance of TSTMs 08Z-18Z. No significant easterly wind
component is expected.

KBUR...Moderate confidence in 18Z TAF. There is a 30% chance of
IFR conditions 08Z-16Z. Also, there is a 10-15% chance of TSTMs
08Z-18Z.

&&

.MARINE...17/950 AM.

For the Outer Waters, moderate to high confidence in current
forecast. Through tonight, high confidence in winds and seas
remaining below Small Craft Advisory (SCA) levels. For Friday
through Monday, there is a 30-50% chance of SCA level winds,
especially across PZZ673/676 during the afternoon and evening
hours.

For the Inner Waters, high confidence in current forecast. Today
through Monday, winds and seas are expected to remain below SCA
levels for all of the Inner Waters.

&&

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

&&

$$

PUBLIC...Rorke/Schoenfeld
AVIATION...RAT
MARINE...RAT
SYNOPSIS...MW

weather.gov/losangeles

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