Ventu Park, California Weather Forecast Discussion

696
FXUS66 KLOX 161039
AFDLOX
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
339 AM PDT Tue Sep 16 2025
Updated marine and aviation sections
.SYNOPSIS...16/253 AM.
High pressure aloft will bring on more day of warming today.
Night through morning low clouds and fog will continue over the
coasts through Wednesday. Moisture from tropical storm Mario will
move into the area later Wednesday through Friday leading to a
chance of showers and thunderstorms, especially on Thursday. Dry
weather is expected over the weekend.
&&
.SHORT TERM (TDY-THU)...16/253 AM.
Today will be the warmest day of the next 7. A large ridge
extending from a 591 dam upper high over El Paso will bring 589
dam hgts to the area. Skies will be sunny across the the vlys and
the interior. Very weak onshore flow will make for a weaker and
later arriving sea breeze. All areas except the Antelope Vly
(little temp change) will see 3 to 6 degrees of warming. This will
push afternoon highs in the vlys up into the mid 90s to 102
degrees. The coasts (away from the beaches) will see highs in the
80s with a smattering of lower 90s. While these temps are above
normal they will come in just under advisory levels.
All eyes on the Wed/Thu/Early Fri portion of the forecast. TS
Mario intensified ydy evening, but has not move much and is still
about 1000 miles south of Los Angeles. It is expected to weaken
and become a remnant low over the next 24-36 hours as it moves
into colder waters. There will likely be some coastal low clouds
in the morning, but later in the morning and in the afternoon
skies will turn mostly cloudy as the mid and high clouds roll in.
PWATs will increase to between 1.5 and 1.75" during the day and
even though the cloud cover will bring some cooling to VTA and LA
counties the increase in humidity will likely make it feel worse.
A little offshore flow develops over the Central Coast and this
will warm that area 2 to 3 degrees. The majority of mdls show the
rain chcs holding off until the evening.
The main slug of mositure (PWATs near 2 inches) and lift is
forecast by almost all mdls to arrive Wednesday night and then
continue Thursday. There is considerable disagreement between mdls
and even within the individual mdls ensembles as to where the
main axis of rain will be. Looking at all possible solutions it
looks like LA county is least likely to receive the brunt of this
system (although it is still possible) with VTA county and SLO/SBA
counties equally likely. TSTMs are just as likely with the system
as are showers and given the high PWATs some areas could receive a
hefty dose of rain. There is good mdl consensus that almost the
entire forecast area will see some rain during the 36 hour period
with a 10 to 20 percent chc that some areas receiving an inch or
more of rain.
This system will come into the forecast window of numerous higher
resolution mdls later today and hopefully increase the confidence
of the main precip axis. That being said, systems coming up from
the south often confound even the best forecast mdls and
everything will need very close watching.
Needless to say with all of the clouds and rain max temps will
tumble on Thursday, but with all of the sub tropical humidity and
rain it will feel rather sultry.
.LONG TERM (FRI-MON)...16/253 AM.
On Friday a weak trof rotates into the state from the west. It
will force most of the moisture to north. The best chc of more
rain will be in the morning, but there is still enough mdl
uncertainty to warrant a 20 to 40 percent chc of a shower or TSTM.
PWATs drop so these storms will likely not produce as much
rainfall as Thursday`s. The rain chc will end quickly in the
evening.
The weekend will be dry. An upper high over nrn Mexico will keep a
weak low pressure system to the west of the Central Coast at bay.
Hgts will rise to about 588 dam. This and the return of mostly
sunny skies will bring two days of warming. Most areas will warm
3 to 4 degrees on Sat and an additional 1 to 3 degrees on Sunday.
By Sunday most of the area will be within a couple degrees of
normal.
The upper low finally moves ashore on Monday. The lowering hgts
and increasing cyclonic flow aloft will likely bring a decent
coastal marine layer to the region. The ensemble consensus brings
2 to 4 degrees of warming to the area, but given the lowering hgts
feel this may not be the right way to go.
&&
.AVIATION...16/1030Z.
Around 0645Z, the marine layer depth was around 950 feet deep at
KLAX. The top of the inversion was around 2000 feet with a
temperature near 27 degrees Celsius.
Moderate confidence in the current forecast for coastal terminals
through 17Z, and again after 03Z Wednesday. Otherwise, high
confidence exists for all remaining terminals.
LIFR to IFR conditions will be prevalent at most coastal
terminals through at least 16Z. VFR conditions should develop by
18Z at the latest. There is a high to likely chance of LIFR to
IFR conditions returning to coastal terminals after 03Z Wednesday.
The highest chances exists for the Central Coast terminals.
KLAX...LIFR to IFR conditions will continue through at least 16Z,
or as late as 18Z. VFR conditions should persist through at least
01Z. There is a 50 percent chance of LIFR to IFR conditions
tonight. The most likely time period for any low clouds and fog at
KLAX will be after 08Z Wednesday. No wind impacts are expected at
this time.
KBUR...VFR conditions are expected through the period. No wind
impacts are expected at this time.
&&
.MARINE...16/338 AM.
High confidence in winds and seas remaining below Small Craft
Advsiory (SCA) levels through Wednesday, with moderate confidence
thereafter through Saturday afternoon. There is a moderate (30-40
percent) chance of low-end SCA winds from around Point Conception
south to San Nicolas Island Wednesday afternoon and evening.
Between Wednesday and Friday, the remnants of Tropical Storm Mario
are expected to affect the southern California coastal waters. A
period of showers, most likely late Wednesday and Thursday, will
move over the waters. Thunderstorms with risk of brief but strong
winds and frequent lightning are possible at any time in the
window. Gusty northeast to east winds nearshore are possible on
Thursday due to the proximity of the core of the weakened storm.
Please monitor the forecast if you have any plans on going out on
the water this week.
&&
.FIRE WEATHER...15/800 PM.
An upper level low pressure system developing off the coast will
likely bring periods of remnant subtropical moisture from tropical
system Mario (currently centered off the coast of southern Baja)
into the region this week. Subtropical moisture will likely stream
into the area starting as early as Tuesday afternoon/night when
there is a 5 to 15 percent chance of dry thunderstorms, with storm
activity mostly staying offshore. The chances of showers and
thunderstorms at times will increase late Wednesday into Friday,
with a decreasing threat into the weekend. The main thunderstorm
threats will be strong/erratic winds, frequent and possibly
pockets of dry lightning, and brief heavy rain inducing flooding.
While isolated dry lightning strikes may occur as early as
Tuesday afternoon into Tuesday night, the greatest threat for
drier thunderstorms and associated fire starts will be Wednesday
afternoon into Thursday morning (especially San Luis Obispo and
Santa Barbara counties) when there will be increased mid level
moisture, more favorable upper level dynamics, and relatively
drier conditions near the surface. With the potential for
strong/erratic outflow winds, fire starts will have the potential
for rapid fire spread. As a result, there is a 30 percent chance
of Fire Weather Watches being issued for portions of the forecast
area in this Wednesday afternoon to Thursday morning time frame.
As deeper moisture moves into the region on Thursday and Friday.
storms will generally become wetter with increasing flooding
concerns. There is a non-zero risk of localized significant flash
flooding/debris flow concerns. Most areas will likely receive
between 0.10 and 0.50 inches between Wednesday and Friday, with
pockets of one inch or greater possible. Rain rates are generally
expected to be less than 0.25 inches per hour, except 10 percent
chance of localized 0.50-1.00 inches per hour. Also of note, as
the remnants of the tropical wave passes through the region
Wednesday night into thursday, there will be the potential for
some gusty southeast to northeast winds, with gusts of 25 to 35
mph for lower elevations, and 40 to 50 mph across the mountains,
which will add to the fire weather concerns if thunderstorms
develop.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
$$
PUBLIC...Rorke
AVIATION...Hall
MARINE...Hall
FIRE...Gomberg
SYNOPSIS...MW
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox

NWS LOX Office Area Forecast Discussion