513
FXUS66 KLOX 281158
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
458 AM PDT Fri Jun 28 2024

Updated Aviation section

.SYNOPSIS...27/1153 PM.

Slight cooling is expected into Friday as high pressure aloft
weakens. Gusty northwest winds will affect southwestern Santa
Barbara County and the Interstate 5 Corridor tonight. Warmer
weather is expected over the weekend as high pressure returns, and
above normal temperatures will continue through next week.

&&

.SHORT TERM (TDY-SUN)...28/401 AM.

An onshore flow pattern remains in place across the area early
this morning. Slight cooling will continue into today as the tail
end of upper-level trough of low pressure moving through the
northern Intermountain Region will brush the area and slightly
increase onshore flow. Night through morning low clouds and fog,
which have struggled to form over the last several nights and
mornings, are becoming more entrenched along the Central Coast of
California this morning, while an eddy circulation near Santa
Catalina Island still struggles to form stratus clouds around it.
The increase in northwest flow over the offshore coastal waters
and parallel to the southern California coastline should permit
the eddy circulation to become a little more vigorous. With the
shallow marine layer depth along the Central Coast, there is a
high-to-likely (40-60 percent) chance of dense fog developing
along the Central Coast this morning. A dense fog advisory might
be needed for the Central Coast later this morning.

500 mb heights start to climb across the region over the weekend
as an upper-level ridge of high pressure over north Texas this
morning strengthens and expands westward. A warming trend is
forecast for Saturday and Sunday across the region, most
pronounced away from the coast. Onshore flow will weaken some, but
still remain intact into early next week. A persistent marine
layer depth will keep at least patchy low cloud coverage for some
coastal areas, but the marine layer depth will be forced to thin
some. A warming trend is well reflected in the forecast, but with
950 mb temperatures to reaching around 35 degrees Celsius across
the warmest areas, dangerously hot conditions are not forecast at
this time. Temperatures will warm to about 5 to 10 degrees above
normal for this time of year, though. Closer to the coast,
temperatures will remain around normal for this time of year with
a continued marine influence continuing and keeping the sea breeze
cooling the land mass during the afternoon hours.

.LONG TERM (MON-THU)...28/406 AM.

The strong upper-level ridge will pull away farther to the east
for early next week and allow for a piece of an upper-level
trough of low pressure over the Gulf of Alaska to brush the area
and increase onshore flow. A little better onshore push should
occur into the valleys and foothill area and bring some cooling
for Monday. Low cloud coverage should increase some and possibly
extend a little farther inland as the marine layer depth deepens
some.

By late week, the story for the weather pattern will change as a
strong high pressure system over the Central Pacific Ocean this
morning will build into the West Coast. A hot air mass will
develop over the region as 500 mb heights potentially reach 600
decameters over the northern California where the ridge center
could end up being anchored. Looking at the latest ensemble
forecast members, there is a moderate-to-high chance of widespread
dangerously hot weather developing across the region for the
latter half of next week. EPS ensemble means suggest high
temperatures means climbing through next Saturday. NBM values
remain in the forecast for high temperatures for late next week,
but as the ridge builds east into Nevada, a southeast flow aloft
could develop and open the door for monsoonal moisture to sneak
in. This could create some more cloudiness and keeps overnight low
temperatures warmer than normal across the region. Minimum
temperatures break away from NBM values toward the latter part of
the forecast period away from the coast. In addition, the marine
layer induced low cloud pattern could become very patchy in
nature or even non-existent as the middle level clouds and warmer
temperatures will mess with low cloud formation.

The increase in subtropical moisture could also develop more
typical afternoon and evening showers and thunderstorms with a
monsoonal flow pattern. EPS ensemble members suggest precipitable
water means climbing close to 1.00 at KLAX. A very slight (10
percent) chance of showers and thunderstorms has been added to the
forecast for the mountains and desert on Thursday and Friday,
breaking away from WPC and NBM values for late week.

&&

.AVIATION...28/1157Z.

At 11Z at KLAX, the marine layer was 1000 feet deep. The top of
the inversion was at 6000 feet with a temperature of 22 C.

High confidence in CAVU TAFs for desert sites and KPRB/KVNY/KBUR,
with southwest wind gusts to 20-30 kt this afternoon and evening
at KPMD/KWJF. Moderate confidence in coastal/coastal-valley TAFs,
with MVFR-IFR cigs/vsbys this morning, clearing out by this
afternoon, and returning late tonight north of Point Conception
and in LA County. Onset and dissipation timing of cigs/vsbys may
vary by around +/- 2 hours from current forecasts. For KOXR/KCMA,
there is a 30% chance for cig/vsby restrictions to develop this
morning and again late tonight.

KLAX...Moderate confidence in TAF. Aside from onset/dissipation
timing uncertainty, 30% chance for cigs to become IFR and vsbys to
become MVFR this morning and again late tonight into Sat morning.
No significant east wind component is anticipated.

KBUR...High confidence in CAVU TAF.

&&

.MARINE...28/155 AM.

There is a moderate threat of dense fog late tonight into Friday
for the waters along the Central Coast.

Moderate confidence in the forecast for Gale conditions ending by
3 AM this morning across the outer waters from the Central Coast
to San Miguel Island. Moderate to high confidence in Small Craft
Advisory (SCA) winds through late this morning. Winds below SCA
levels are then expected through Saturday morning across the
waters. Winds will then increase to SCA strength from the
northwest across the outer waters Saturday night through Monday
night. There is a 40-50 percent chance of High-end SCA winds of
20 to 30 knots across the outer waters, and a 40 percent chance of
Gales for the waters from the Central Coast to San Miguel Island.
SCA winds are likely to spread into the nearshore waters off the
Central Coast, and into the Santa Barbara Channel Sunday afternoon
into Sunday night.

Steep, shorter period seas will affect the outer waters and
portions of the nearshore waters through Monday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 11 AM PDT this morning
      for zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Saturday for
      zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...Hall
AVIATION...Cohen
MARINE...Smith
SYNOPSIS...jld/Smith

weather.gov/losangeles

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