Duarte Weather

000
FXUS66 KLOX 021209
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
509 AM PDT Sun Apr 2 2023

Updated Aviation Discussion

.SYNOPSIS...02/211 AM.

A weak storm system will bring cooling and some unsettled weather
to the region today through Monday night with gusty winds and
some shower activity. A ridge may build into the region later in
the week, which bring could widespread above normal temperatures
to the area next weekend.

&&

.SHORT TERM (TDY-TUE)...02/310 AM.

All fcst mdls predict that an eddy will spin up and bring low
clouds to many of the coasts and vlys. So far this has not
happened, but there are some hints of it starting up over LA
county so will keep the forecast but it may well be sunnier than
fcst. Slowly falling hgts and weaker offshore flow from the north
will bring 2 to 4 degrees of cooling to the area.

A big onshore push to the east will occur later this afternoon and
it will produce strong (55 mph gusts) advisory level winds across
the western half of the SBA south coast and a wind advisory covers
the area from this evening through early Monday morning. Otherwise,
increasing onshore flow combined with an eddy circulation will
likely bring a return of low clouds and patchy fog for most
coasts, valleys, and northern interior areas later tonight into
Monday morning. The rapid deepening of the marine layer may well
produce either light rain or patchy drizzle, especially for LA
county.

A strong inside slider will bring strong northerly upper level
winds(90-100 knots at 500 mb, 50-60 knots at 700 mb) and cold air
advection to the area on Monday and esp Monday night.

The first effect of this system will be the formation of
orographic showers sometime later this evening into early morning
across the northern mountains, including the I-5 cooridor. There
is still a little uncertainty in how fast the snow levels will
fall, but it looks likely that snow levels will drop to pass level
(3500 ft). A dusting to two inches of snow is possible above 3500
feet, with highest accumulations above 5000 feet. There is a
40 percent chance of an inch of snow on the I-5 near Tejon Pass.

The second and more important condition will be the winds.
Warning level gusts from 60 to 75 mph look likely across the mtns
and the Antelope Vly where High Wind Watches are in effect. It now
looks like warning level winds may push into the Santa Clarita
Vly and a High Wind Watch is now in effect there as well. Almost
all of the rest of the forecast area will need strong wind
advisories as well. The peak of the wind event will occur from 6pm
to midnight Monday night. Mtn Wave activity is likely with this
event due to the orientation and strength of the upper level
winds. If a mtn wave touches down over the one of the vlys it
could cause substantial damage and this threat will have to be
monitored closed during the peak hours.

All of the winds will clear the low clouds and Monday should see
sunny skies by the afternoon. The sunshine will not help the max
temps too much as the strong cold air advection will cool the csts
and vlys 4 to 8 degrees and the interior by 10 to 15 degrees. Max
temps will come in a few degrees either side of 60 across the
csts and vlys.

Tuesday will be much less active with dry NW flow over the area.
Max temps will rise 2 to 5 degrees under sunny skies. There will
be some left over winds and wind advisories may be needed during
the morning hours in locations that experienced warning level
winds Monday night.

.LONG TERM (WED-SAT)...02/318 AM.

EC and GFS deterministic mdls as well as the GEFS and EPS ensemble
mdls all agree that a nice warm up is in store for the xtnd
period. Dry NW flow will persist on Wed and Thu. A weak and dry
trof will move over the are Thu night and Fri morning followed by
a building ridge nosing in from the E Pac.

Weak offshore flow from the east and moderate offshore flow from
the north will combine to not only keep any marine layer stratus
from forming but to also bring 4 to 5 days of warming to the area.

Look for 3 to 5 degrees of warming on Wed, 5 to 6 degrees on Thu,
2 to 3 on Fri, and 2 to 5 degrees each day Sat and Sun. Max temps
will reach normals (finally) Friday and then exceed them over the
weekend when many vly locations will have highs in the 80s.

&&

.AVIATION...02/1207Z.

At 0701Z at KLAX, the marine layer was 800 ft deep, with a
inversion with at top at 2100 ft and a max temp of 13 C.

High confidence in KWJF and KPMD TAFs.

Low to moderate confidence in remaining TAFs due to large
uncertainty in arrival timing and hgt of cigs. Arrival of cigs
may be off by +/- up to 3 hours. There is a 30% chance of no cigs
for KSBA, KOXR, KCMA, and KSMO.

KLAX...Moderate confidence in TAF. MVFR cigs may arrive between
12Z-16Z. There is a 20% chance of east winds of 8 kt until 16Z.

KBUR...Moderate confidence in TAF. There is a 40% MVFR cigs could
arrive anytime between 09Z-15Z.

&&

.MARINE...02/312 AM.

High confidence in Small Craft Advisory (SCA) level winds
continuing across the waters from the Central Coast to the
western Santa Barbara Channel through this afternoon. Winds may
briefly fall below SCA level this morning but are expected to
pick back up in the afternoon. By early this evening winds will
likely strengthen further and SCA level conditions will expand
into the waters adjacent to LA and Orange Counties (strongest west
of Catalina Island). These gusty winds will persist through
Monday then gradually diminish Tuesday into Wednesday. For the
outer waters from the Central Coast to San Nicolas Island, there
is a high chance of Gale force gusts tonight through Monday night,
and for the waters closer to shore there is a 50-60 percent
chance of Gales, highest along the Central Coast and in the Santa
Barbara Channel. Gale Watches have been issued for all the waters.
Tonight, in addition to wind, large and hazardous steep seas over
10 feet are expected to develop across the outer waters and reach
heights such as 8 to 9 feet in the inner waters. These seas are
expected to last through at least Tuesday. After the Gale Watches
expire expect SCA level conditions to persist, possibly until the
next afternoon increase of gusty NW winds expected Tuesday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Watch in effect from Monday evening through late
      Monday night for zone 88. (See LAXNPWLOX).
     High Wind Watch in effect from late tonight through late
      Monday night for zones 345-353-376>383. (See LAXNPWLOX).
     Wind Advisory in effect from 6 PM this evening to 5 AM PDT
      Tuesday for zones 349-351. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 2 AM PDT Monday for
      zones 645-650. (See LAXMWWLOX).
     Gale Watch in effect from late tonight through late Monday
      night for zones 645-650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 2
      AM PDT Monday for zone 655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 PM PDT this evening
      for zones 670-673-676. (See LAXMWWLOX).
     Gale Watch in effect from this evening through late Monday
      night for zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke
AVIATION...Rorke/Schoenfeld
MARINE...Schoenfeld/Smith
SYNOPSIS...Munroe/Smith

weather.gov/losangeles

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

NWS LOX Office Area Forecast Discussion