114
FXUS66 KLOX 210615
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1015 PM PST Thu Nov 20 2025

.SYNOPSIS...20/530 PM.

A storm will bring rain and mountain snow to the area through
Saturday morning, heaviest tonight into Friday morning in Los
Angeles County. Gusty east winds are expected Friday in some
areas. High pressure will push temperatures back to normal this
weekend which will continue through the holiday week.

&&

.SHORT TERM (THU-SUN)...20/723 PM.

Showers continue across the area this evening as the main rain band
with the system has exited the area. Generally, rain amounts
between 0.25 and 0.50 inch have occurred across the coastal and
valley areas, so far, with up 0.75 inch in the foothills and
mountains. The colder air mass aloft with the storm system is
punching into the Central Coast as the system`s upper-level center
slides through over San Luis Obispo County. Showers will likely
become more scattered to numerous overnight tonight and into
Friday morning. Jet dynamics, trailing near Point Conception will
stretch this broader circulation and allow for a low level
circulation to spin up in the southern California bight later
tonight. This will likely enhance showers over Los Angeles County
overnight tonight and into Friday morning, steepening lapse rates
and providing some extra instability.

Some concern exists for a moderate to strong offshore flow event
for Friday night and into Saturday morning as the system rotates
farther to the south. A `wet` Santa Ana wind pattern could develop
between Friday night and Saturday. The latest NAM-WRF solutions
advertise 40-45 knots at 950 mb and 850 mb, which ride high wind
warning criteria, while EPS solutions lean more on the side of a
moderate advisory for the typical locations, such as KSDB, K3A6,
and KCMA. Deterministic NAM-WRF solutions could be the outlier of
the solutions, so the best approach is to wait for more data. The
next shift will be briefed about the possibility of offshore
winds across the region.

***From Previous Discussion***

Very little has changed with the assessment of this storm and the
expected impacts aside from the arrival of rain today was a few
hours ahead of schedule. The initial round of precipitation has so
far lived up to its billing of mostly light rain under a tenth of
an inch per hour. This will more or less remain the case through
early this evening as it advances through LA County. Meanwhile,
along the Central Coast rain will be tapering off this afternoon
and evening in most areas except for the far interior sections
east of the Santa Lucias where scattered showers may continue into
Friday morning. Amounts there have been under a half inch in most
locations so far and any additional rain is expected to be on the
lighter side.

For the second part of the storm tonight into Friday models have
been consistent showing a very favorable severe weather threat
across LA County, and in particular the southern part of the
county. A strong vorticity lobe is expected to pinwheel around Pt
Conception later tonight, resulting in backing winds inland and
northwest flow over the Santa Monica Bay resulting in a large
scale counter-clockwise rotation centered right over southern LA
County. The forecast sounding for KLAX shows the backing winds
towards the surface and a hodograph that could certainly support
rotation and a small tornado. CAPE values close to 1000J/kg will
support moderate updrafts that will be favorable for storm
initiation. Overall, the pattern looks consistent with previous
severe weather outbreaks, either from strong straight line winds
from storms, heavy rain, or from a small tornado. The most
favorable area appears to be southeast LA County from Pasadena to
LA/Orange County line, but this could shift east or west depending
on the ultimate track of the upper low.

Periods of heavy rain are likely at times overnight in LA County
and high res models continue to indicate a 10-20% chance of rain
rates reaching 1 inch per hour. WPC also has this area in a
marginal risk for flooding. This will be a much more scattered
heavy rain event than the last event so not all areas will get
these rates, but the areas that do will could have significant
hydrologic impacts.

The heavy rain potential is expected to decrease Friday morning,
however, scattered showers are possible through the day with rain
rates generally a quarter inch per hour or less.

Also of interest Friday is the increase in northeast winds
creating a semi-wet Santa Ana event across portions of LA and
Ventura Counties. A low end wind advisory may be needed tomorrow
in the usual Santa Ana wind favored areas.

While the Santa Ana wind will have a detrimental affect on the
shower chances across the coast and valley areas, the north facing
mountain slopes will benefit from upslope flow that will maintain
the shower potential into Saturday. Can`t completely rule out a
shower at lower elevations but any precip would be isolated and
brief.

Several inches of snow in the mountains are expected with this
system with the snow level around 6000 feet. Could see 8-12 inches
of snow by Saturday in the LA County mountains above 8000 feet
with the beneficial upslope flow Friday and Saturday.

Sunday is expected to be dry but on the cooler side.

.LONG TERM (MON-THU)...20/226 PM.

While temperatures might cool a little on Sunday as the east winds
turn off and return to a more normal onshore pattern, temperatures
will remain around normal through next week (including
Thanksgiving). The marine layer with low clouds and fog should
also make a return, but might be limited by Wednesday as north
winds start to form. A rain-free period through at least Black
Friday looks almost certain. There are growing signals however for
another storm sometime in the Saturday through Tuesday time range
(Nov 29-Dec 2).

&&

.AVIATION...21/0615Z.

At 0505Z at KLAX, there was no marine layer. There was a deep
moist layer extending to over 6000 feet.

Low confidence in all TAFs through 21Z with frequent changes in
both cig and vis. Better confidence in VFR conds aft 21Z

KLAX...Low confidence in TAF through 21Z. Cig and Vis will vary
frequently with cigs possible anywhere from BKN008 to BKN040. Vis
will likely vary from 2SM To 6SM in RA and BR. Better confidence
in VFR cigs aft 21Z. Good confidence that there will be at least
a 8kt east wind component through at least 02Z with a 18kt east
wind component possible through 15Z.

KBUR...Low confidence in TAF through 21Z. Cig and Vis will vary
frequently with cigs possible anywhere from BKN008 to BKN040. Vis
will likely vary from 2SM To 6SM in RA and BR. Better confidence
in VFR cigs aft 21Z.

&&

.MARINE...20/724 PM.

Low confidence in forecast, especially regarding winds. It is
best to alter any plans and remain in safe harbor until conditions
improve this weekend.

A storm system will continue to move south before stalling
inside the Southern California Bight, bringing periods of gusty
winds, a large west- northwest swell (especially for the Outer
Waters), rain, and possible thunderstorms into the weekend. The
highest thunderstorm chances are from tonight into Friday morning.
Any thunderstorm can produce erratic wind shifts, heavy rain,
lightning, and even waterspouts. There is a 10% chance of brief
Gale Force winds south of Point Conception through late tonight.

A combination of Small Craft Advisory (SCA) winds and seas will
be common across the coastal waters through much of the weekend.
Seas will increase to 10-12 feet across the Outer Waters, 10 feet
for the nearshore Central Coast Waters, and 4 to 6 feet inside
the Southern California Bight by late tonight. Wind directions
will vary considerably through the course of the storm which will
will result in rough, confused seas, especially south of Point
Conception.

NE winds will become common tonight through Saturday morning as
the core of the storm system remains nearly stationary and spins
inside the Southern California Bight. Winds will be strongest from
Ventura to Santa Monica (20-30 knots), but NE winds gusting up to
25 knots will occur nearshore from Palos Verdes south through
Orange County. NE winds may reach the Channel Islands, but much
lower chances for Catalina Island.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Flood Watch in effect until 7 AM PST Friday for zones
      88-362-366>373-379-380-548. (See LAXFFALOX).
     High Surf Advisory in effect until 3 AM PST Monday for zones
      340-346. (See LAXCFWLOX).
     High Surf Advisory in effect from 3 AM Friday to 3 AM PST
      Monday for zone 354. (See LAXCFWLOX).
     Winter Weather Advisory remains in effect until 10 AM PST
      Friday for zone 377. (See LAXWSWLOX).
     Winter Weather Advisory remains in effect until 4 PM PST
      Friday for zones 379-380. (See LAXWSWLOX).
PZ...Small Craft Advisory in effect until 3 AM PST Friday for zone
      645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PST Saturday for
      zones 650-655-670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Hall/MW
AVIATION...Rorke
MARINE...Lewis/CC
SYNOPSIS...MW/RK

weather.gov/losangeles

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