San Dimas, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

426
FXUS66 KLOX 220430
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
830 PM PST Thu Nov 21 2024

.SYNOPSIS...21/729 PM.

Increasing clouds but dry weather expected through Friday
afternoon. Rain chances will develop along the Central Coast
Friday evening then spread across Los Angeles and Ventura
Counties Saturday. Another round of rain is expected later
Sunday into Monday.

&&

.SHORT TERM (THU-SUN)...21/828 PM.

***UPDATE***

Forecast issues in the short term include cold overnight
temperatures again in the interior wind-sheltered valleys, with a
Frost Advisory now in effect for the Ojai Valley. There is also
the potential for coastal fog, along the Central Coast and
portions of the Oxnard Plain and the LA Basin. There is a low
chance of patchy dense fog in these areas during the late night to
early morning hours, but confidence is low that this will occur.
For now will leave dense fog out of the forecast but will maintain
mention of low clouds and patchy fog for portions of the coast.

Otherwise, dry weather is expected through early Friday afternoon,
with mostly clear skies across much of the area. High clouds will
begin to spread over northwest San Luis Obispo County late tonight
into Friday, with rain chances beginning along the northern
Central Coast Friday afternoon. Rain is then forecast to spread
northwest to southeast across the area Friday night through
Saturday, as the first storm impulse impacts the area.

***From Previous Discussion***

A large and powerful cyclone continues to spin off the Pacific
Northwest coast. It has been drifting west along 50N with smaller
upper lows as far south as 40N pinwheeling around each other.
This overall pattern is expected to remain through at least early
next week. In the meantime southwest California will be on the
very southern edge of a couple of rain bands that will move
through the area starting later Friday. Most of the ensemble
solutions continue to strongly favor low impacts locally.

The first impulse Friday night into Saturday (LA County mainly
late morning to mid afternoon Saturday), will be the weaker of the
two. This will be a 2-5 hour period of light rain in most areas
with rain rates under a tenth of an inch per hour and totals
under a quarter inch (except upslope areas of NW SLO County and
southwest SB County where amounts up to a half inch are possible.

Sunday will be dry for most of the day except along the Central
Coast when the next band of rain from this cyclone arrives in the
late morning into the afternoon.

.LONG TERM (MON-THU)...21/228 PM.

After around a 24-36 hour period of little to no rain, a second
and slightly stronger system will come through the area Sunday
into Monday and possibly lingering into Tuesday, though the lions
share of the rain falling later Sunday into Monday. Ensembles
have trended weaker with this one, though still at least a little
stronger than the first batch due to a stronger southerly flow
component that will provide a slight boost to the rain amounts and
rates as well as a longer duration of rain. As a result, upslope
areas such as NW SLO County and southern Santa Barbara County
could receive 1-2 inches of rain with peak rates around a third of
an inch per hour. Still well below any thresholds for flooding or
debris flows. Outside of the upslope areas, rain amounts of a
half to one inch expected.

While most of the system will be over by Monday evening, the
area will remain in a moist westerly flow through Tuesday with
off and on light rain possible through the day. Overall, a fairly
gloomy damp day.

Ensembles now show much lower rain chances for the latter half of
next week with slowly warming temperatures, though still slightly
below normal through the period.

&&

.AVIATION...22/0009Z.

At 2300Z at KLAX, there was no marine layer. There was a surfaced
based inversion with a top at 1900 ft and a temperature of 20 C.

Overall, moderate confidence in 00Z TAF package. For tonight into
Friday morning at KPRB, KSMX, and KSBP, MVFR/IFR cigs are
expected. There is a 40% chance for minimum cigs to be off by a
category (LIFR flight cat possible). There is a 30% chance for
cigs to become IFR at KOXR and MVFR at KCMA tonight. There is a
30% to 40% chance cigs become IFR or lower from 10z to 20z at
KLGB. Arrival times of cigs/vsby restrictions may be off +/- 2
hours. Otherwise, high confidence in VFR conditions, and light
winds expected.

KLAX...Moderate confidence in 00Z TAF. There is a 30% chance of
BKN005-BKN015 from 10z to 18z. No significant easterly wind
component.

KBUR...High confidence in 00Z TAF.

&&

.MARINE...21/822 PM.

For the Outer Waters, buoy observations confirm that seas are
decreasing to below Small Craft Advisory levels. Sub Advisory
conds should persist through Friday Afternoon. There is a 40%
chance of SCA level winds Friday evening into Saturday morning for
eastern portions of PZZ670. Otherwise, SCA conditions are
unlikely across the coastal waters through at least Tuesday.

For the Inner Waters north of Point Sal, there is a 50 to 60%
chance of SCA level winds Friday evening into Saturday morning.
Otherwise, SCA conditions are unlikely through at least Tuesday.

For the Inner Waters south of Point Conception, high confidence in
conditions remaining below SCA levels through Tuesday.

Areas of light rain will occur at times this weekend through next
week.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory in effect from 2 AM to 8 AM PST Friday for
      zone 357. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 PM PST this evening
      for zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/Smith
AVIATION...Black
MARINE...Black
SYNOPSIS...MW/Smith

weather.gov/losangeles

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