Claremont, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

597
FXUS66 KLOX 191112
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
312 AM PST Fri Dec 19 2025

.SYNOPSIS...19/307 AM.

Mostly clear skies will cover the area today and Saturday save for
some morning low clouds. It will be cooler each day but high
temperatures will remain above normal. There will be increasing
clouds, cooler temperatures and a slight chance of rain over San
Luis Obispo county Sunday and Monday. A strong storm will bring
many inches of rain to the entire area Tuesday through Wednesday.

&&

.SHORT TERM (TDY-SUN)...19/1245 AM.

The strong 592 dam upper high that brought all of the warm weather
this week will be pushed to the south today. The flow aloft will
flatten out into the W to E configuration and hgts will fall to
582 dam. The offshore flow from the E will turn onshore and then
increase through the day. Offshore flow from the N will remain
but will be weaker than ydy. Look for low clouds and patchy dense
fog to develop across the LA cst, western SBA county and the Paso
Robles area. Skies, otherwise will be mostly sunny. The change in
the sfc flow as well as the falling hgts will lead to 3 to 6
degrees of cooling across the csts/vlys. The lack of cool air
advection from the San Joaquin Vly will lead to 2 to 4 degrees of
warming across the interior.

Flat westerly flow will continue over the area on Saturday. Hgts
will dip down to 579 dam. Onshore flow to the east will increase
from 1 mb in the morning to about 3 mb in the afternoon, the
offshore flow from the north will turn weakly onshore in the
afternoon. The onshore flow and falling hgts will bring plenty of
low clouds to most of the csts and lower vlys in the morning. The
increasing onshore flow in the afternoon will slow clearing and
more than a few beaches may be cloudy all day. The southern
progress of the atmospheric river (AR) affecting the northern
portion of the state is no forecast to remain north of the area
which will eliminate the rain threat for SLO county and reduce the
amount of mid and high clouds over the area. The cooling trend
will continue as falling hgts and better onshore flow combine to
lower most temps another 3 to 6 degrees. The Central Coast will
be the exception with little change in temps. Max temps, however,
will remain above normal (3 to 6 degrees interior csts, 5 to 10
degrees vlys and 10 to 15 degrees mtns and far interior).

.LONG TERM (MON-THU)...19/300 AM.

Sunday and Monday will be fairly similar days. The upper flow
pattern will slowly tilt more and more into a SW to NE direction
on Sunday as the AR system sags a little more to the south. A
slight chc or chc (20 to 30 percent) of rain will develop over
northwestern SLO county. Other areas will just see increasing
clouds Sunday and mostly cloudy skies Monday. Rainfall totals
during the two day period will most likely be under a tenth of an
inch. Max temps will fall 2 to 4 degrees across almost all of the
area Sunday and then will change little on Monday. Max temps will
remain above normal (1 to 2 degrees across the csts; 4 to 8
degrees vlys and 8 to 16 degrees mtns and interior).

Deterministic, ensemble based and AI based mdls have been in very
good agreement up until now. Annoyingly quite a bit of
disagreement has now shown up. The following forecast is based on
a broad mixture of all available mdls, but now the confidence is
lower esp for Tue and Thu.

On Tuesday the flow will tilt to the SW. The southern end of the
AR will be swept up by a trof and will also assume a SW to NE
orientation. The trof will translate eastward and will bring rain
to the area. Rain will become likely (60 to 70 percent chc) across
the Central Coast in the morning, while a chc (20 to 40 percent
chc) develops south of Pt Conception. Rain is a near certainty
across SLO and SBA counties in the afternoon. Ventura County will
see a 50 percent chc and LA county a 40 percent chc. By Tuesday
evening the entire 4 county area will be engulfed by rain. Due to
the southerly flow associated with this event the south facing
slopes will see the highest totals and rates. Right now from dawn
Tuesday to dawn Wednesday it looks like most areas will see about
an inch of rain with the south facing slopes receiving about two
inches. Snow levels during this time will be near 8000 ft. All
this said there are several solutions (notably the GFS and many of
its ensembles) that are slower with the arrival of the AR - this
outcome would lead to a much drier day.

The best confidence remains on Wednesday when the AR should move
across the entire area. Wednesday should feature the most rainfall
and the highest rainfall rate. It should rain all day across all
of the area. It is likely that 1 to 2 inches of rain will fall
across the csts/vlys and 2 to 4 inches across the foothills and
mtns. The interior as usual will see less rain likely around an
inch to an inch and half. Due to the strong south flow snow levels
will remain near 8000 ft.

Pretty low confidence for the Christmas forecast. Many mdls move
the bulk of the rain out of the area in the morning with much
lighter rain in the afternoon. There is still the potential for 1
to 2 inches of additional rain, but this might be on the high side
of potential outcomes. Will have to wait and see which way the
mdls take this days forecast. Colder air will be ushered in behind
the AR and snow levels will fall through the day ending up around
7000 ft late in the afternoon and then falling to 6000 ft
overnight. It will be a coolish day with max temps only in the
lower to mid 60s for most of the csts/vlys.

Model agreement falls off pretty rapidly after Thursday, but there
is a potential for more rain Fri Sat and Sun.

&&

.AVIATION...19/1023Z.

Around 09Z, there was no marine layer depth at KLAX. There was
surface-based inversion up to around 2100 feet with a temperature
near 24 degrees Celsius.

Low-to-moderate confidence in the current forecast for terminals
north of Point Conception and coastal terminals south of Point
Conception, otherwise moderate-to-high confidence. There is a
high-to-likely chance of VLIFR to LIFR conditions for terminals
north of Point Conception and coastal terminals south of Point
Conception through 18Z. There is a high-to-likely chance of LIFR
to IFR conditions after 03Z Saturday at coastal and valley
terminals. Otherwise, VFR conditions will persist.

KLAX...There is a 60 percent chance of VLIFR to LIFR conditions
at KLAX through 18Z, then there is a 30 percent chance of MVFR
visibilities lingering into the afternoon hours. There is a 70
percent chance LIFR to IFR conditions as soon as 03Z Saturday or
as late as 10Z Saturday. Any easterly winds should remain less
than 7 knots.

KBUR...VFR conditions are expected through at least 08Z. There is
a 30 percent chance of LIFR conditions after 08Z Saturday,
increasing to 50 percent after 12Z Saturday. No wind impacts are
expected at this time.

&&

.MARINE...19/223 AM.

Moderate-to-high confidence in the current forecast. High
confidence in the forecast for winds through early Monday morning,
then moderate confidence thereafter. Moderate confidence exists
in the sea forecast through tonight, then higher confidence
thereafter.

A shallow marine inversion over the coastal waters will bring
at least patchy dense fog at times this morning.

For the waters southwest through northwest of the Channel Islands
and the nearshore waters along the Central Coast, there is a
likely-to-imminent (60-90 percent) chance of Small Craft Advisory
(SCA) level winds through tonight, highest during the afternoon
and evening hours and from near Point Concpetion south to San
Nicolas Island. There is a low-to-moderate (20-40 percent) chance
of SCA conditions over the weekend and into Monday, then there is
a likely (60-80 percent) chance of widespread SCA conditions on
Tuesday and Tuesday night with a moderate-to-high (30-50 percent)
chance of GALES.

Inside the southern California bight, there is a moderate-to-high
(30-50 percent) chance of SCA level winds this afternoon and
evening, highest across the western portion of the Santa Barbara
Channel. Winds and seas should drop below SCA levels over the
weekend and into Monday, there is a high-to-likely (50-60 percent)
chance of widespread SCA conditions on Tuesday and Tuesday night.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from noon today to 9 PM PST
      this evening for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 PM PST this evening
      for zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 AM PST Saturday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke
AVIATION...Hall
MARINE...Hall
SYNOPSIS...30

weather.gov/losangeles

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