Six Flags Magic Mountain, California Weather Forecast Discussion

216
FXUS66 KLOX 161655
AFDLOX
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
955 AM PDT Tue Sep 16 2025
.SYNOPSIS...16/912 AM.
High pressure aloft will bring one 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 and
cooler temperatures. Dry weather is expected over the weekend.
&&
.SHORT TERM (TDY-THU)...16/954 AM.
***UPDATE***
The marine layer lowered down to under 1000 feet everywhere
overnight. As a result, one more day of warming is expected today
before remnants of Mario arrive tomorrow with increasing clouds
and shower chances. The 24 hour change map shows most of
LA/Ventura Counties above about 500 feet elevations are trending
at least 5-10 degrees warmer than yesterday and as much as 20
degrees warmer in the Santa Monica Mountains. For this reason a
Heat advisory was issued for many of the valleys of LA/Ventura
Counties as well as the Santa Monica Mountains until 7pm this
evening. Temperatures are expected to lower 3-6 degrees tomorrow
as moisture and some cloud cover from Mario arrive, though
humidities are expected to rise so there is a small chance
(5-10%) that another heat advisory will be needed.
No big changes in the forecast for the incoming remnants of Mario.
Showers are still likely across a large portion of the 4 county
area later tonight into Thursday along with some isolated
thunderstorms. Will have more details with the afternoon
discussion but not expecting the overall message to change.
***From Previous Discussion***
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...16/1652Z.
At 1630Z at KLAX, the marine inversion was around 500 feet deep.
The top of the inversion was 1700 feet with a temperature of
28 degrees Celsius.
For the 18Z TAF package, high confidence in valley and desert
TAFs as VFR conditions are expected through the period.
For coastal TAFs, low to moderate confidence in 18Z TAFs. Moderate
confidence in KSMX with timing of flight category changes +/- 2
hours of current forecast. For remainder of coastal TAFs, there is
a 20-30% chance of LIFR/VLIFR conditions 08Z-16Z.
KLAX...Overall, moderate confidence in 18Z TAF. High confidence in
VFR conditions through this evening. For tonight, there is a 30%
chance of LIFR/VLIFR conditions 09Z-16Z. No significant easterly
wind component is expected.
KBUR...High confidence in 18Z TAF as VFR conditions are
anticipated through the period.
&&
.MARINE...16/940 AM.
For the Outer Waters, high confidence in current forecast. Today
through Saturday, winds and seas are expected to remain below
Small Craft Advisory (SCA) levels with only a 20% chance of SCA
level winds around Point Conception Wednesday afternoon and
evening.
For all the Inner Waters, high confidence in current forecast.
Today through Saturday, wind and seas are expected to remain below
SCA levels.
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.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory in effect until 7 PM PDT this evening for zones
      88-357-358-362-369>374. (See LAXNPWLOX).
PZ...NONE.
&&
$$
PUBLIC...MW/Rorke
AVIATION...RAT
MARINE...Hall/RAT
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