Acton Weather

084
FXUS66 KLOX 310800
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1200 AM PST Wed Dec 31 2025

.SYNOPSIS...30/523 PM.

Santa Ana winds will continue tonight and Wednesday under mostly
cloudy skies. A storm system will move into the area from the
south Wednesday with periods of rain through at least Saturday,
heaviest Wednesday night into New Years Day.

&&

.SHORT TERM (WED-SAT)...30/753 PM.

***UPDATE***

Wind Advisories expired at 3 PM this afternoon for the gusty Santa
Ana winds that began on Monday. Isolated stronger gusts still
remain in the most wind-favored areas this evening, including
Porter Ranch, Wiley Ridge, and a few locations in the Santa Monica
Mountains with gusts 35 to 50 mph. The northeast to east winds
will persist into Wednesday afternoon, then are expected to shift
to the southeast, even as rain begins to overspread the area.

An upper low southwest about 400 miles southwest of Point will
remain nearly stationary through Wednesday afternoon, then
shifting northeast fairly rapidly, reaching the Central Coast
Thursday morning. Light rain is expected to begin at around
midnight tonight, with areas of moderate rain expected to begin
Wednesday afternoon. The heaviest rain will likely occur Wednesday
night through Thursday morning, with thunderstorms possible after
midnight through Thursday afternoon.

RAIN: Light rain will gradually increase across the area tonight
and Wednesday. The peak of the rainfall in the short term will be
Wednesday night through Thursday afternoon with a lingering shower
threat Thursday night and Friday.

Totals through New Years Day will generally range from 0.75 to
2.50 inches across coastal and valley areas with 2.00-5.50 inches
across the foothills and mountains. An additional 0.10-0.50 is
likely on Friday with the lingering shower threat.

Rainfall rates are expected to be in the 0.25 to 0.50 inch per
hour range. However, there will be locally higher rates of around
0.50-1.00 inch per hour Wednesday night and Thursday associated
with heavier pockets of rain and potential thunderstorms.

SNOW: Snow levels through New Years Day should remain above 8500
feet then drop to around 7500 feet on Friday. So, do not
anticipated any significant winter weather issues through Friday.

THUNDERSTORMS: As the heaviest rain moves across the area
Wednesday night and Thursday, there will be some enhanced
instability. So, have included a chance of thunderstorms into the
forecast Wednesday night through Thursday afternoon. At this time,
the threat of any severe thunderstorms looks to be minimal. Will
continue to monitor the situation closely.

WIND: Santa Ana winds began to diminish early this afternoon.
Tonight through Wednesday, high resolution models decrease the
gradient by about half from the peak this morning and decrease the
upper level support. So, any advisory-level winds are expected to
remain localized. For Wednesday night and Thursday, there will
be some gusty southeasterly winds associated with the storm systems.
However, any advisory-level winds look to remain localized.

IMPACTS: Given the expected rainfall totals and rainfall rates,
there is concern for significant hydrologic issues from southern
Santa Barbara county southward. A FLOOD WATCH is in effect from
1000 PM Wednesday through 1000 PM Thursday (see LAXFFALOX for
details).

There will be an enhanced risk of rockslides and mudslides across
canyon roadways. Widespread urban flooding is likely along with
debris flows in and around the recent burn scars. Strong flows
will be likely in local waterways.

.LONG TERM (SUN-WED)...30/125 PM.

For the extended, 12Z models continue to exhibit decent synoptic
agreement. The overall message will be a continued wet pattern
across the area through Tuesday.

Models differ somewhat in the timing of things, but a series of
impulses will move across the area through the extended period. At
this time, the two best shots of rain will be on Saturday then
again on Tuesday, but rain will be possible through the entire
period. With either system, light to moderate amounts of
additional rainfall are likely. Snow levels on Saturday will be
above 7500 feet, but will drop into the 6000-7000 foot range
Sunday through Tuesday. So, some accumulating snowfall will be
likely at the higher elevations into early next week.

&&

.AVIATION...31/0800Z.

At 0555Z at KLAX, there was a shallow surface inversion with a
top of 600 feet with a temperature of 22 C.

Good confidence in TAFs through 16Z then lower confidence due to
uncertainty with cig/vis fcst as rain moves over area. MVFR cigs
and or vis is possible at any site 16Z. There is a greater chc of
MVFR cig/vis after 01/00Z.

Isolated -SHRA are possible through 16Z. Good confidence that -RA
will overspread the area between 16Z and 20Z. There is a slight
chance of -TSRA after 01/06Z, especially south of Pt. Conception.

Lgt ocnl mdt turbc and LLWS is likely over and near hier terrain,
especially across Los Angeles and Ventura counties through the
forecast period.

KLAX...Good confidence in TAFs through 16Z. Then moderate
confidence with a 30 percent chc of 4SM -RA BR BKN025 conds
16Z-04Z. A 20 percent chc of 3SM -TSRA BKN010CB after 01/06Z.
There is a 30 percent chc of a 10kt east wind component through
16Z. Good confidence in a 10+ kt east wind component aft 01/06Z.

KBUR...Good confidence in TAFs through 16Z. Then moderate
confidence with a 30 percent chc of 4SM -RA BR BKN025 conds
16Z-04Z.

&&

.MARINE...30/856 PM.

Offshore winds linger into tonight and possibly Wednesday morning,
and the SCA for the Santa Barbara Channel was extended into
Thursday as winds increase from the south as the low approaches.
Confidence is higher in widespread SCA level winds from the east
to southeast impacting the region (including harbors) as early as
Wed afternoon and continuing through at least late Wed night as
another storm makes its presence felt across the region. There is
a 30% chance for Gale Force Winds during this period, highest
chances from Santa Cruz Island and northward. May need a Gale
Watch for this time period if confidence increases. A relative
lull is possible Thursday afternoon and evening, but a return of
SCA level south to southwest wind is likely Friday into Saturday,
especially north and west of Point Conception as a cold front
moves through the area.

A steep and choppy southerly wind swell will accompany the winds,
peaking Wednesday night into Thursday. By Friday, a west to
northwest swell will accompany the secondary storm coming through.
This swell will be larger and a longer period.

Rain will likely be heaviest Wednesday (New Year`s Eve) night
through Thursday (New Year`s Day). There is a chance of
thunderstorms (mainly south of Point Conception) during this
period, but confidence is low in timing. Waterspouts, gusty and
erratic winds, frequent lightning, and brief heavy rain are all
possible with any thunderstorm.

&&

.BEACHES...30/856 PM.

Abnormally large tides between 6.8 and 7.5 feet MLLW will occur
during the morning hours, roughly between 4am and noon Wednesday
through Sunday. Surf heights remain relatively small through
Friday, although moderate south-southeast winds and a wind swell
from the south-southeast will add a little bit to the water
levels. There may be a risk for some minor tidal overflows through
Friday, with best chances Thursday and Friday. There is a
moderate chance for a Beach Hazards Statement to be issued for
Thursday and Friday for a majority of the beaches.

Saturday and Sunday pose more of a threat for moderate coastal
flooding as a larger swell from the west-northwest enters the
region. While there exists some uncertainty in timing of the
highest surf, this would be the best chance for impacts such as
shallow flooding of parking lots and roadways, some inundation of
harbor walkways, and more significant beach erosion. There is a
moderate chance for a Coastal Flood Advisory to be issued for
Saturday and Sunday, highest for west facing beaches.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Flood Watch in effect from this evening through Thursday
      evening for zones 88-349>358-362-366>382-548. (See LAXFFALOX).
PZ...Small Craft Advisory in effect until 10 AM PST Thursday for
      zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect from 8 AM this morning to 1 PM
      PST this afternoon for zone 673. (See LAXMWWLOX).
     Small Craft Advisory in effect from 7 AM this morning to 7 AM
      PST Thursday for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...Thompson/Ciliberti
AVIATION...Rorke
MARINE...Phillips/Lewis
BEACHES...Lewis
SYNOPSIS...MW/Ciliberti

weather.gov/losangeles

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