583
FXUS66 KLOX 140318
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
818 PM PDT Mon Oct 13 2025

.SYNOPSIS...13/728 PM.

A rare October storm system will bring widespread rain tonight
through Tuesday, with a threat of pockets of heavy rain and
thunderstorms. There is a significant risk of debris flows, road
flooding, and isolated wind damage. Temperatures will remain well
below normal through Wednesday, with steady warming to follow
through the weekend.

&&

.SHORT TERM (MON-THU)...13/751 PM.

***UPDATE***

The heavy-weight October storm has entered Monterey County and is
poised to start its run through the forecast area. Some light pre
frontal showers have already popped up across the 4 county area
with even LAX reporting some light rain falling. The latest high
rez mdl runs confirm the current forecast with frontal passage
and attendant heaviest rain will occur over SLO county between
10pm and 2am; SBA county midnight to 4am; VTA county 3am to 7am
and LA county from 6am to 10 am.

There has been no forecast decrease in intensity of this storm and
many if not all of the recent burn areas will likely experience
some form of flooding/debris flows. A FLASH FLOOD WATCH remains in
effect for all 1st and 2nd year burn scars through Tuesday
afternoon.

***From Previous Discussion***

A rare and very potent storm system remains on track to affect
the area tonight through tomorrow, with lingering showers possible
into early Wednesday. All areas will see rain. Some areas will
see short bursts of heavy rain, although it remains difficult to
predict exactly where. South-facing slopes and foothills have the
highest chance of seeing those heavy bursts, but they can happen
anywhere.

Rainfall totals remain on target, with 0.75 and 1.50 inches
common, except 2.00 to 4.00 inches in the favorable south facing
slopes and anywhere those heavy bursts form. An isolated reading
of 5 inches is on the table, especially over the San Gabriels
where computer projections show the highest totals. Peak rainfall
rates of 0.33 to 0.66 inches per hour will be common, which
should be enough to cause plenty of minor road issues and heavy
traffic for the Tuesday morning commute - as well as shallow
debris flows impacting a few roads near a burn scar. A few lanes
or offramps could be flooded. Rockslides in canyon roads are
nearly certain. Isolated rates to around 1.00 inches per hour are
also likely, but again not exactly sure where. Wherever those
occur, impacts will be locally amplified. If they occur in an
urban area, several lanes of a freeway could flood. If they occur
over a burn scar, a deeper more significant debris flow would form
which could cover and close a road and or threaten structures.
That is a real possibility, with the Palisades, Eaton, and
southern Bridge burn scars having the highest threat.

In addition to the hydro risks, there is a significant threat for
severe thunderstorms capable of producing very localized but
damaging winds and or a tornado. Still seeing several signatures
(the trajectory of the low, the diffluence aloft, the high shear
environment) for supercell thunderstorms with several high
resolution models resolving finer scale parameters conducive of
isolated strong downdraft winds and/or weak tornadoes (updraft
helicity being one of them).

What should people do? For tonight through Tuesday: Avoid outdoor
activities and stay indoors as much as possible, especially if
you hear thunder, see lightning, or experience sudden wind
shifts. Avoid parking near tall trees. Be ready for sudden power
outages. Avoid the roads as much as possible, and if you have to
drive, allow extra time as traffic will be increased due to
slippery roads, low visibility, and localized flooding. If you are
near a burn scar, there is a risk of significant debris flows.
Heed the advice of local officials, and expect at the very least
mud and debris on some roads. Boaters, please stay in safe harbor.
For everyone, stay tuned to your local news outlet and
weather.gov for any updates.

In addition, there will be a period of gusty southwest winds
focused over the interior areas. Snow levels remain high (above
7,000 feet) for the majority of the precipitation, but they lower
to 5,500 to 6,000 feet after the main rain later on Tuesday. So
while this is not a big snow maker of a storm, any post frontal
showers could be some light accumulations down to 6,000 foot
elevations.

By Wednesday afternoon or evening, any linger showers should end.
Drying and warming northwest to north winds will quickly follow
Wednesday Night and turn northeasterly on Thursday. Gusts in the
20 to 35 mph range are the most likely outcome. Temperatures will
increase as a result, along with a warming airmass, with highs in
the 70s common by Thursday.

.LONG TERM (FRI-MON)...13/249 PM.

Some models are showing the northeast flow that forms on Thursday
increasing some more on Friday then decreasing through Saturday.
Meanwhile high pressure will be building over the southwest.
Temperatures will continue to rise as a result, with highs in the
mid 70s to mid 80s common Friday through the weekend.

&&

.AVIATION...14/0207Z.

At 2355Z at KLAX, there a was 4400 ft deep moist layer.

Low confidence in the TAF. A strong cold front will pass through
the area and will exit LA county around noon on Tuesday (14/20Z).
Strong south winds ahead of the front will create areas of TURBC
over and near to hier trrn.

Both Cigs and Vis will vary frequently as the front nears passes
over every site. There is a 30 percent chc of TSTMs with the front
and a 20 percent chc during the afternoon behind the front.

KLAX...Low confidence in TAF. Cigs and Vis will vary frequently
08Z-20Z. There is a 30% chance of a thunderstorm from 12Z to 18Z
Tue. High confidence in a 10-15 kt east wind component 13Z-17Z.

KBUR...Low confidence in TAF. Cigs and Vis will vary frequently
08Z-20Z. There is a 30% chance of a thunderstorm from 12Z to 18Z
Tue.

&&

.MARINE...13/726 PM.

Tonight through Tuesday afternoon, a storm system and associated
cold front will move across the region. This will bring a 20-40%
chance of thunderstorms to all of the coastal waters during that
timeframe. Any thunderstorms that form may be capable of frequent
cloud to surface lightning, gusty and erratic winds with locally
higher, choppy seas, small hail, and even a waterspout. Please
see the latest Marine Weather Statement (LAXMWSLOX) for further
details.

For the outer waters and inner waters N of Point Sal, Small Craft
Advisory (SCA) level south winds are expected (60%-70% chance)
with the cold front tonight into Tuesday morning, then decreasing
from the west behind the front Tuesday afternoon through Tuesday
night. Wednesday through Thursday increasing NW winds will likely
reach SCA levels once again. Best chances south of Point
Conception. Conds should then be below SCA levels Friday through
Saturday night.

For the inner waters south of Point Conception, S to SW winds
increasing to SCA levels are expected across the area mainly
tonight into Tuesday morning as the front approaches and moves
through the region. There is a 50% chance of Gale Force winds
over these waters later tonight into early Tuesday. The strongest
winds will be north of Santa Cruz and Anacapa Islands and along
the coast from Point Mugu to Point Dume. Conds should then be
below SCA levels Tuesday night through Saturday night.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 8 AM PDT Tuesday for zones
      38-342>345-351>353. (See LAXNPWLOX).
     Flood Watch remains in effect through Tuesday afternoon for
      zones
      38-88-342-344-345-348-353-355-358-362-368>375-377>380-548. (See LAXFFALOX).
     Wind Advisory in effect until 2 PM PDT Tuesday for zones
      376>383. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 AM PDT Tuesday for
      zone 645. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Tuesday for zones
      650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT Tuesday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Kittell/Rorke
AVIATION...Rorke
MARINE...Sirard/Ciliberti
SYNOPSIS...RK/CC

weather.gov/losangeles

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