112 
FXUS66 KLOX 290003
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA 
503 PM PDT Tue Mar 28 2023

.SYNOPSIS...28/127 PM.

Rain and mountain snow will spread into the region through tonight
as a storm system originating from the Gulf of Alaska digs into 
the region. A showery and unsettled weather pattern will linger 
for Wednesday and Thursday. Dry but cool conditions are expected 
for Friday through the weekend.

&&

.SHORT TERM (TDY-FRI)...28/210 PM.

An upper low continues to spin just west of the coast near the
CA/OR border. Racing out ahead of it is a fast moving cold front
that will sweep through the area tonight into early Wednesday.
Forecast for this storm remains largely unchanged. There will be a
6-8 hour period of light to perhaps briefly moderate rain, 
mostly overnight tonight but lasting into the morning hours in LA
County. Hi res ensembles continue to advertise rain rates mostly
around a tenth of an inch per hour, but locally up to a quarter
inch in the foothills and mountains. The mean wind speeds in the 
lower levels aren't particularly strong, topping out around 25-30kt
from the southwest so the upslope enhancement won't be as strong
as earlier storms this winter and likely favoring the Santa Lucias
the most. Rain amounts during this part of the storm are expected
to be around a half inch at lower elevations and up to an inch or
so in the foothills and mountains. Snow levels will be around 
6000', possibly lowering to 5000' at the very back edge early 
Wednesday.

Winds are starting to pick up ahead of the front, especially
across interior SLO County and wind advisories are in effect
there through tonight.

Following the frontal passage tonight into early Wednesday there 
will be at least a few hours of little to no rain and likely even 
some sunshine (especially south of Pt Conception) before the 
colder and more unstable part of the system arrives later 
Wednesday into Thursday. Models show a favorably positioned 130kt
jet across southern LA County along with rapidly cooling
temperatures aloft that will increase lapse rates. CAPE values
aren't particularly impressive but the other factors are strong 
enough to warrant at least a slight chance of thunderstorms 
through early Thursday. Precip will be much more showery during 
this phase of the storm so amounts will be highly variable but
overall another half inch or so is expected on average with
locally higher amounts in thunderstorms, where rain rates could
briefly reach a half inch per hour. Also can't rule out
waterspouts over the ocean and small tornadoes over land given the
favorable position of the jet and upper low

Showers and storms expected to taper off Thursday with dry but
cool weather Friday. Deterministic models show a secondary trough
coming through the area, though model clusters suggest it will be
weaker than what the GFS/ECMWF are indicating. And in any case 
none of the ensembles show any rain with it so mainly just
continued below normal temperatures.

.LONG TERM (SAT-TUE)...28/217 PM.

Air mass warms Sat/Sun as heights rise. In addition, weakening
onshore flow, even going slightly offshore to the north will
generate additional warming at the surface that should bring highs
to the lower 70s in some areas both days. 

A weak trough and increasing onshore flow return Monday/Tuesday
which at the very least will result in some cooling area-wide.
There are a few ensemble solutions that show some light precip
later Monday into Tuesday, justifying the small rain chances
across parts of the area, however, it's more likely that rain will
stay north of the area. The remainder of next week looks dry at
this point.

&&

.AVIATION...29/0002Z.

At 2330Z, the marine inversion at KLAX was based at 700 feet.
The top of the inversion was 1600 feet with a temperature
of 14 degrees Celsius. 

Overall, low to moderate confidence in 00Z TAF package. Through
the TAF period, rain will overspread the area this evening through
Wednesday morning. Lower confidence in forecast due to changes in
the CIG/VSBY category changes. Generally, conditions are expected
to drop to MVFR levels, with a 20-30% chance of brief period of
IFR conditions with heavier rain. 

KLAX...Moderate confidence in 00Z TAF. High confidence in
development of MVFR conditions, in rain, after 07Z. However, low
confidence in timing of flight category changes with respect to
both CIG and VSBY. No significant easterly wind component is
expected. 

KBUR...Moderate confidence in 00Z TAF. High confidence in
development of MVFR conditions, in rain, after 07Z. However, low
confidence in timing of flight category changes with respect to
both CIG and VSBY.

&&

.MARINE...28/946 AM.

Ahead of a cold front, a period of Small Craft Advisory (SCA) 
level S-SW winds is expected. This will occur from mid morning 
thru this evening in the northern outer waters zone (PZZ670), from
noon thru this evening in the inner waters north of Pt. Sal, from
noon thru late tonight in the central outer waters zone (PZZ673),
and from late this afternoon thru late tonight in the southern 
outer waters zone. There is a 40-50% chance of SCA level SW-W 
winds in the SBA Channel tonight, and sub-advisory S-SE winds into
early Wed morning for the southern inner waters.

SCA level SW-W winds are likely in the southern two outer waters 
zones Wed night, with a 30-40% chance of SCA level winds elsewhere.
However, seas may reach SCA levels in the northern outer waters 
and northern inner waters zones Wed night into early Thu anyway. 

A period of SCA level W-NW winds is likely across the entire waters
Thu night, except just a 40% chance in the southern inner waters.
At this time, SCA conds are not expected across the waters Fri thru
Sat.

There is a slight chance of thunderstorms across the waters Wed
thru Thu morning. Some storms could produce small hail, gusty 
winds, dangerous lightning and possibly waterspouts.

&&

.BEACHES...28/1212 PM.

Large swell in the coastal waters may bring marginal high surf 8 
to 12 feet on Central Coast beaches on Wednesday and Thursday and
4 to 7 feet on Ventura beaches on Thursday. This is a fairly low
confidence forecast with only a 50 percent chance of reaching
criteria. However, there will be a high risk of rip currents on 
many beaches Wednesday and Thursday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 5 AM PDT Wednesday for zones
      38-342-344-345. (See LAXNPWLOX).
     High Surf Advisory in effect from 11 AM Wednesday to 8 AM PDT
      Thursday for zones 340-346. (See LAXCFWLOX).
     Winter Weather Advisory in effect from 2 AM Wednesday to 10
      AM PDT Thursday for zones 353-376-377. (See LAXWSWLOX).
     High Surf Advisory in effect from 8 PM Wednesday to 8 PM PDT
      Thursday for zone 354. (See LAXCFWLOX).
     Winter Weather Advisory in effect from 5 AM Wednesday to 2 PM
      PDT Thursday for zone 378. (See LAXWSWLOX).
     Winter Weather Advisory in effect from 4 AM Wednesday to 2 PM
      PDT Thursday for zone 379. (See LAXWSWLOX).
     Winter Storm Warning in effect from 4 AM Wednesday to 2 PM
      PDT Thursday for zone 380. (See LAXWSWLOX).
     Wind Advisory in effect from noon Wednesday to 6 AM PDT
      Thursday for zones 381>383. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
      for zones 645-670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Wednesday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW
AVIATION...RAT
MARINE...Sweet/DB
BEACHES...Sweet/DB
SYNOPSIS...MW

weather.gov/losangeles

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