259
FXUS66 KLOX 201531
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
831 AM PDT Mon May 20 2024

.SYNOPSIS...20/228 AM.

Low clouds will continue through the morning will better clearing
in the afternoon. Breezy onshore winds will continue this afternoon
and evening. More sunshine with slight warming is expected
Tuesday and Wednesday as onshore flow weakens. Then cooler with
increasing marine layer clouds again the latter half of next week.

&&

.SHORT TERM (TDY-WED)...20/831 AM.

***UPDATE***

Typical May-Gray morning across the district. Stratus has pushed
well inland to the coastal slopes with mostly clear skies
elsewhere. Current sounding data indicate marine inversion ranging
in depth from 2300 feet north of Point Conception to around 3400
feet south of Point Conception. Some drizzle has been observed
this morning with even some very light measurable amounts across
the foothills.

Overall, no significant issues are anticipated in the immediate
short term. Morning stratus should clear to the coast by late
morning early afternoon with some coastal areas remaining mostly
cloudy through the afternoon. With the onshore flow and widespread
marine influence, temperatures today will remain a few degrees
below seasonal normals. There will be some gusty southwesterly
winds across interior sections this afternoon/evening, but any
advisory-level winds will remain localized (in such areas as Lake
Palmdale).

Overall, current forecast has good handle on the immediate short
term. So, no significant updates are expected.

***From Previous Discussion***

Clearing was a little better last evening but persistent onshore
flow as well as a weak eddy have steadily brought the low clouds
back to the csts/vlys and onto the coastal slopes. Weak north flow
across SBA county may keep portions of the SBA south coast clear.
A weak trof will transverse the area this morning and it will
provide enough lift to create a few pockets of morning drizzle.
The trof will also weaken the inversion and this coupled with
offshore trends should allow for a little better and a little
earlier clearing. Lower hgts from the trof will cool the
csts/vlys a little but the interior will see 4 to 8 degrees of
cooling. Max temps today will be in the 60s across the csts/vlys
and in the 70s for most of the interior. These temps are 6 to 12
degrees blo normal. It will again be a breezy afternoon across the
interior and esp the western Antelope Vly and foothills were there
will be local advisory level gusts.

The forecasted offshore trends for tonight are now weaker and its
doubtful that the marine layer will be affected too much (it will
likely keep the clouds out of the mtns) Look for most of the
csts/vlys to fill with low clouds and only the bare minimum of
canyon winds in the mtns.

2 to 3 mbs of offshore trends Tuesday afternoon are not strong
enough to bring offshore flow to the area but the weakened onshore
flow will allow for a much more complete clearing and a delayed
seabreeze as well as a slower return of the low clouds in the
evening. More sunshine and a weaker sea breeze as well as rising
hgts will all combine to bring 3 to 6 locally 8 degrees of
warming to the area. Even with this noticeable warm up max temps
will still come in 4 to 8 degrees below normal.

Wednesday will be the nicest day of the next 7. The marine layer
will cover most of the coasts but not as much into the vlys. There
will be good clearing and max temps will rise another 1 to 3
degrees, but will still not reach normals.

.LONG TERM (THU-SUN)...20/1223 AM.

Both deterministic and ensemble mdl fcsts agree that the xtnd fcst
will be dominated by long wave troffing. Many ensembles also show
a little short wave embedded in the broad cyclonic flow moving
over the state Friday night.

Also mdls show the E Pac High increasing and the interior
afternoon thermal sfc low strengthening. This will bring a return
of strong W to E onshore flow.

Look for the marine layer to increase again covering much of the
csts and vlys and xtndg into the mtns passes. Clearing will be
delayed with many coastal areas seeing no clearing at all. The
trof passage on Friday night may bring some drizzle to the area
Saturday morning.

The strong onshore flow will bring gusty possibly advisory level
winds to the interior particularly the western Antelope Vly and
foothills.

Max temps will drop both on Thu and Fri as the marine layer and
onshore flow increases. Max temps on Friday across the csts and
vlys will mostly be in the 60s with just a very few vly sites
hitting 70 degrees. Max temps will end up 5 to 10 locally 12
degrees blo normals. Max temps over the weekend will change little
from Friday`s chilly values.

&&

.AVIATION...20/1015Z.

At 0815Z at KLAX, the marine layer was 1700 ft deep. The top of
the inversion was at 5000 feet with a temperature of 17 C.

Good confidence in desert TAFs.

Moderate confidence in the remainder of the TAFs. There is a 20
percent chc of no clearing at coastal site in the afternoon. If
clearing does develop it may differ from fcst by +/- 90 minutes.
There is a 40 percent chc of no drizzle at sites where it is fcst.
There is a 30 percent chc at any cstl site of MVFR cigs returning
by 03Z.

KLAX...Moderate confidence in TAF. There is a 40 percent chc of no
drizzle. There is a 20 percent chc of BKN025 conds persisting
through the afternoon, otherwise SCT conds could arrive anytime
20Z-22Z. There is a 30 percent chc of BKN015 conds develop at
21/03Z and a 20 percent chc not until 10Z. There is a 30 percent
chc of a 6 knot east wind component thru 15Z.

KBUR...Moderate confidence in TAF. There is a 40 percent chc of no
drizzle. SCT conds could arrive STDAFDLOXanytime 18Z-20Z. Low clouds may
not redevelop until 21/11Z.

&&

.MARINE...20/254 AM.

High confidence in Small Craft Advisory (SCA) seas and/or
northwest winds continuing over the offshore waters from the
Central Coast to San Nicolas Island through at least Tuesday and
likely beyond. There will likely be brief and slight lulls each
morning. There is a 30 percent chance of SCA for the western
Santa Barbara Channel each evening. SCA conditions are unlikely
elsewhere. Fairly large seas will continue as a result, with
short period dominant seas over most nearshore waters.

A long period south to southwest swell will peak through Monday
with heights of 2 to 4 feet. This will create larger than usual
breaking waves nearshore as well as some stronger currents near
most harbor entrances.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through this evening for
      zones 87-362-366. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday for
      zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke/Thompson
AVIATION...Rorke
MARINE...Kittell
SYNOPSIS...MW

weather.gov/losangeles

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