La Crescenta, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

905
FXUS66 KLOX 211823
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1023 AM PST Thu Nov 21 2024

Updated Aviation and Marine sections

.SYNOPSIS...21/840 AM.

Fair skies and dry weather will continue today and most areas
will see some warming as well. Rain chances will develop along the
Central Coast Friday evening then across Los Angeles and Ventura
Counties Saturday. Another round of rain is expected later Sunday
into Monday with lesser possibilities Tuesday.

&&

.SHORT TERM (TDY-SAT)...21/858 AM.

***UPDATE***

As mentioned below a very nice day today and most of Friday as
well. Still a few mountain areas with some gusty winds but well
below advisory levels. A very dry day today with humidities
already dropping below 10% across some interior areas.

12z models so far not straying too far from the previous
expectations for the incoming storm. The first impulse coming
through Friday night into Saturday with amounts under a half inch
in most areas, and for southern areas likely under a quarter inch.
For the LA area rain likely holding off until later morning hours
Saturday. The duration of rain expected to be around 3-6 hours in
any one location.

More uncertainty with the timing for the next impulse but most of
the solutions are suggesting later Sunday into Monday. A little
stronger than the first but still likely in the "beneficial rain"
category with very low chances of any significant issues.

***From Previous Discussion***

Very pleasant day on tap today (as opposed to the chaos occuring
up north) Srn CA sits under the western half of a weak ridge. At
the sfc there is weak offshore flow from the east and weak onshore
flow to the north. Most areas will warm today and today will be
the warmest day of the next 7 for the csts/vlys.

A cold front will develop in the potent system to the north on
Friday and will begin to move to the south. It will approach the
Central Coast during the afternoon. Some low clouds may develop
across the coasts in the morning but otherwise skies should be
mostly clear through the morning. The afternoon will see an
increase in clouds as the front nears the area. A slight chc of
rain will develop over the coastal section of SLO county later in
the afternoon. Max temps will cool across the csts and vlys but
will warm some across the interior sections of LA county.

The upper low that is driving this cold front and is bringing the
very wet and windy weather to Nrn CA will not move too much to the
south and this means that the cold front will not have that much
dynamics associated with it and that SRN CA will not experience
the dangerous weather that this storm produced to the north.

The front will bring rain to the Central Coast Friday night.
South of Point Conception...rain is likely to develop overnight
across southern SBA county, there will be a chc of rain for VTA
county and LA county will only have a slight chc.

On Saturday the front will bring rain to SLO/SBA counties in the
morning, it will likely be raining in VTA county and a chc of rain
will extend into LA county. During the afternoon rain is likely
across the entire 4 county area.

Rain is likely across LA county in the evening while the chc of
rain will continue across the rest of the area due to the very
moist (but not very dynamic) moisture plume moving over the area.

Total rainfall for the the Friday night through Saturday evening
period will range from a half inch to an inch across SLO and SBA
counties to a quarter inch to three quarters of an inch for VTA
and LA counties. Some upslope areas may recieve more. The one
likely exception will be the far NW corner of SLO county where as
much as three inches of rain may fall. Rainfall rates are not
expected to be worrisome...about a tenth of an inch or less
except around a quarter inch in upslope areas. Snow levels will
be over 8000 feet so no snow issues expected.

Max temps will fall to their usual rainy day upper 50s and 60s.

.LONG TERM (SUN-WED)...21/300 AM.

Sunday will likely be a mostly dry day, however, there are enough
ensemble members with rain to keep a chc or slight chc (20-30
percent) in the forecast for the day. Skies will likely be mostly
cloudy and max temps will remain in the 60s.

The second impulse of the system is a little trickier to forecast
than the first. It involves the upper low to the north weakening
and wobbling to the south. As it does this it should rotate an
impulse around its backside and into the state. There is a lot of
uncertainty on how this will exactly play out as the ensembles are
all over the place. Right no the mostly likely (but lower
confidence) outcome will be for another round of rain affecting
the area from Sunday night into Monday morning with rain lasting
into Monday afternoon. Rainfall amounts for this system now look
similar to the Friday night Saturday system: generally a quarter
to an inch with locally higher amounts across the upslope areas.
This rainfall forecast has seen many changes over the last few
runs and expect it will change a few more times before the system
arrives. Once again snow levels will be over 8000 feet.

The Tuesday/Wednesday forecast is extremely low confidence as the
mdl are really struggling with pattern that will develop. The
ensembles are all over the place. For now will just broad brush in
some low pops and partly to mostly cloudy skies and hope that
there is some mdl convergence soon.

&&

.AVIATION...21/1822Z.

At 1800Z at KLAX, the marine layer was 400 ft deep. The top of
the inversion was at 3000 ft with a temperature of 17C.

Moderate to high confidence in TAFs. For tonight into Friday
morning at KPRB, KSMX, and KSBP, MVFR/IFR cigs are expected --
with a 40% chance for onset times of restrictions to vary by
+/- 3 hours from current forecasts, a 40% chance for minimum cigs
to be off by a category, and a 40% chance for cig restrictions to
continue through the day on Friday. There is a 20% chance for
cigs to become MVFR/IFR at KOXR and KCMA tonight. Otherwise, high
confidence in VFR conditions, and light winds expected.

KLAX...High confidence in TAF. No significant easterly wind
component.

KBUR...High confidence in TAF.

&&

.MARINE...21/1022 AM.

Lingering areas of 10-11-ft seas warrant Small Craft Advisories (SCAs)
across the northern and central Outer Waters (PZZ670/PZZ673) through
early this evening. There will be a 20% chance for SCA winds over
PZZ670 and northern PZZ673 Friday afternoon and evening. Otherwise,
SCA conditions are unlikely across the coastal waters through next
week. Areas of light rain will occur at times this weekend through
next week.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 9 PM PST this evening
      for zones 670-673. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke
AVIATION...Cohen
MARINE...Cohen
SYNOPSIS...MW/Smith

weather.gov/losangeles

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