Weather Service Report

FXUS66 KLOX 230639 AAA

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA 
1139 PM PDT Wed Sep 22 2021

Updated aviation section

.SYNOPSIS...22/124 PM.

Increasing onshore flow will bring cooling to most areas Thursday
and Friday with high temperatures back to normal levels. The
cooling trend is expected to continue into next week.


.SHORT TERM (WED-SAT)...22/858 PM.


Marine layer clouds were sparse south of Point Conception today,
and cleared over land early. This is consistent with the seasonal
change, as we tend to see much less of a marine layer influence in
autumn. Some clouds lingered in the Santa Barbara Channel and clung
near the Ventura County coast. Today was hot over the interior
valleys with some cumulus development over the mountains.

Below advisory level sundowner winds have begun for the western
portions of the Santa Barbara south coast tonight. These winds 
will help to keep the Santa Barbara Channel clear overnight. There
is some uncertainty as to which, if any coastlines south of Point
Conception will see marine layer clouds. Currently, thinking the
best chance is for some brief cloud development near the Ventura
County coast. The marine layer remains very shallow, 500-300 feet
at VBG and LAX respectively. Due to the low, strong inversion, 
patchy dense fog is expected for areas seeing low clouds. 

Thursday, high temperatures will trend a few degrees cooler as a
upper level disturbance to the southeast begins to align with the
trough to the north. The forecast looked on track, and small 
adjustments were made to the cloud cover.

***From Previous Discussion***

For Friday either not much change or slight cooling. Overall a
similar day as Thursday though with increasing marine layer
stratus for coastal zones south of Pt Conception.

Models continue to struggle with the handling of a trough and
eventual pinching off of a closed low late Friday into Saturday.
At one time models showed this happening off the coast of Pt
Conception but now the favored location is northern Baja. This
puts So Cal in an easterly flow pattern aloft with some energy 
and moisture wrapping around, though mostly south of LA County.
Will keep in some low pops for the eastern LA Mountains and
Antelope Valley but not looking particularly favorable at this
time. Still a chance the low could make a closer pass to our area
and require some increasing of pops but for now staying pretty
conservative given the daily model fluctuations. Temperature- 
wise probably very similar to Friday.

.LONG TERM (SUN-WED)...22/137 PM.

Hard to have too much confidence in a detailed extended forecast 
given the difficulties models are having in the short term. And 
big ensemble spreads in temperatures next week also a sign that 
the range of possible solutions is still quite high. However, in
general the vast majority of the models point towards a cooler 
pattern through mid week. A few solutions suggest some light 
precip associated with another trough coming through the region 
but it's still early in the season for that and would defintely 
favor a dry solution right now.



At 0530Z, the marine layer depth was around 400 feet deep at KLAX.
The top of the marine inversion was around 1500 feet with a 
temperature near 29 degrees Celsius.

Moderate confidence in the current forecast for coastal terminals.
High confidence for valley and desert terminals. Less confidence
in timing. Higher confidence in flight categories.

LIFR to IFR conditions will likely spread into coastal terminals
north of KNTD. There is a moderate (30-50 percent) chance of 
similar conditions for coastal terminals south of KNTD. There is a
moderate chance of VLIFR conditions for terminals north of Point
Conception between 08Z and 14Z. VFR conditions should develop
around 16Z.

KLAX...There is a 50 percent chance of LIFR to IFR between 12Z and
16Z. VFR conditions should develop around 16Z. Any south or
southeasterly winds will remain less than 7 knots.

KBUR...VFR conditions are expected through the period.


.MARINE...22/919 PM.

High confidence in Small Craft Advisory (SCA) level winds
continuing through late tonight from Point Conception to San
Nicolas and extending into the western portion of the Santa
Barbara Channel. For the waters adjacent to LA/Orange Counties,
have cancelled the SCA but local gusts to 25 kt are possible
through late tonight across the western portion from Anacapa
Island to Catalina Island. High confidence that winds and seas
will remain below SCA level Thursday through Monday. Short-period,
choppy wind-driven seas will continue through the period across
all the waters. With the shallow marine layer, there will likely 
be patchy dense fog with visibility of one nautical mile or less 
across the coastal waters through Thursday morning.


PZ...Small Craft Advisory in effect until 3 AM PDT Thursday for
      zones 650-673-676. (See LAXMWWLOX).



No significant hazards expected.




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