333
FXUS66 KLOX 160554 AAA
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1054 PM PDT Thu Aug 15 2024

updated aviation discussion

.SYNOPSIS...15/834 PM.

A high pressure system in place over the region will weaken and
move east over the coming days as an upper-level trough moves into
the Pacific Northwest. A cooling trend with increased onshore flow
will establish through the weekend, then some warming will develop
over the early half of next week.

&&

.SHORT TERM (THU-SUN)...15/911 PM.

An upper-level ridge of high pressure remains over the southern
California region this evening. A warm air mass in place with
minimal marine layer induced low cloud coverage the last several
days will start to transition as onshore flow strengthens Friday
and over the weekend. An increasing onshore flow pattern will be
brought to us by strengthening southwest flow aloft between high
pressure system retreating to the east into Texas Panhandle and
an upper-level trough digging into the Pacific Northwest. Night
through morning low clouds and fog will become more pronounced
along the beaches through the weekend, especially along the
Central Coast where ocean water temperatures are cooler. With the
shallow marine layer depth in place, any low clouds could form
dense fog.

A northerly surface gradient remains in place across the area this
evening. Gusty Sundowner winds are surfacing right now and a wind
advisory remains in effect across southwestern Santa Barbara
County this evening. There is a chance that the advisory could be
cancelled early as the KSBA-KSMX surface gradient is showing some
signs of weakening this evening. With winds riding near advisory
levels, the wind advisory was left intact for now and observations
will be monitored closely.

A few tweaks were made to temperatures to reflect the overall
trend, otherwise the forecast is in reasonable shape.

*** From Previous Discussion ***

Broad high pressure aloft currently centered over the region will
be bumped to the east towards Texas tomorrow, as a trough stalls
west of Oregon. This will commence a stagnant upper level
pattern, with SoCal located between a trough and the high pressure
center. Temperatures will be within a few degrees of normal for
most areas, however contrary some more typical patterns, coastal
locations are more likely to be warmer than normal through the
weekend. Tomorrow temperatures will warm slightly, followed by a
cooling trend for the weekend, when 500 mb heights are lower and
onshore gradients strengthen.

Marine layer cloud coverage this morning was confined to west-
facing Santa Barbara County, and this is expected to continue for
tomorrow. Marine layer clouds are expected to increase somewhat
this weekend as lower heights cause some lifting and onshore flow
intensifies.

A Wind Advisory is in effect from 4 PM this afternoon through 3
AM tomorrow morning for the Santa Barbara Southwest Coast and
adjacent Santa Ynez mountains. While the general trend across
high resolution models shows a slight decrease in Sundowner winds
tonight, there remains a 50-70% chance of northwest winds tonight
gusting at 35 to 50 mph. Sundowner wind are likely to occur again
Saturday night. The dry and warm offshore winds will lead to
daytime highs several degrees above normal across the whole Santa
Barbara South Coast (including Santa Barbara City), today and
Saturday.

Monsoonal thunderstorm activity is not favored through the
weekend, although the outer edge of a moisture surge may bring
some high clouds to the region tomorrow afternoon. This moisture
is expected to be too elevated to increase thunderstorm chances,
which continues to be well under 10 percent.

.LONG TERM (MON-THU)...15/244 PM.

The latest ensemble members have come to good agreement on the
general upper level heights for the region. Heights are expected
to climb each day through Wednesday and will peak around 593 to
595 dam. Temperates will trend upwards along with the increase in
heights with moderate HeatRisk impacts for a large portion of the
region Tuesday and Wednesday. There is about a 15 percent chance
that Heat Advisories will be needed for some deserts and valleys.

Marine layer clouds will be shallow with minimal inland extend
due to high 500 mb heights, however the overall onshore flow
pattern in the long term will support overnight-to-morning clouds
at times for the coasts.

Monsoonal moisture transport into the region becomes a bit more
likely on Tuesday and Wednesday, with about 20 percent of ensemble
members hinting towards a favorable upper level flow pattern.
Even so, at this point the chance of actual convection remains
less than 10 percent.

&&

.AVIATION...16/0553Z.

At 05Z at KLAX, the marine inversion was 600 ft deep. The top of
the inversion was 1500 ft with a temperature of 28 deg C.

High confidence in generally CAVU 06Z TAFs for KPRB, KSBA, KOXR,
KCMA, KBUR, KVNY, KPMD, KWJF. Exception is brief MVFR vsbys late
tonight into Fri morning at KSBA, KOXR and KCMA.

Moderate confidence in the 06Z TAFs for the LA coastal airfields.
There is a 40%-50% chance of IFR cigs between 11Z to 17Z at KLAX
and KLGB, and a 20% chance of these conds at KSMO.

Moderate confidence in the 06Z TAFs for KSMX and KSBP. There is a
40-50% chance of VLIFR conds at KSMX between 11Z-16Z due to
cigs/vsbys, and the arrival of cigs could be off by +/- 2 hours
from TAF time. There is a 10%-20% chance of IFR-LIFR cigs/vsbys at
KSBP between 12-15Z.

KLAX...Moderate confidence in the 06Z TAF. There is a 40%-50%
chance of IFR cigs between 11Z to 17Z, or that they occur only
briefly during this time. There is also a 40%-50% chance of IFR
cigs moving in aft about 09Z Fri night. No significant east wind
component is expected.

KBUR...High confidence in the CAVU 06Z TAF.

&&

.MARINE...15/806 PM.

For the outer waters from the Central Coast to San Nicolas Island
(the outer waters), high confidence in Gale force wind gusts
through late tonight. High confidence in Gales subsiding late
tonight, with SCA level winds thru at least the weekend, with the
exception of a 20% chance of Gale force wind gusts in the furthest
northern outer zone Friday evening.

For the nearshore waters off the Central Coast, moderate to high
confidence in SCA level winds and/or steep seas through late
tonight. There is a 40-60 percent chance of SCA conditions again
Friday and Saturday during the afternoon to evening hours, then
lower chances through early next week. On Tuesday, there is a 30
percent chance of SCA winds in the late afternoon and evening.

For the Santa Barbara Channel, moderate confidence in winds below
SCA levels tonight, except for possible local SCA gusts over the
far western portion. Moderate confidence in conditions remaining
below SCA level tomorrow, but higher chances Saturday through
Tuesday, with a 30 percent chance of SCA winds over the western
channel each late afternoon to evening period. In the Eastern
portion, high confidence in conditions remaining below SCA level
through the period.

For the waters off L.A. and Orange Counties, high confidence in
conditions staying under SCA levels through early next week.

With a shallow marine layer, high confidence in dense fog with
visibilities under 1 mile effecting the Central Coast waters
through at least tomorrow morning.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory remains in effect until 3 AM PDT Friday for
      zones 349-351. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Friday for zone
      645. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Friday for zones
      670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Hall/Schoenfeld
AVIATION...Sirard
MARINE...Smith
SYNOPSIS...Hall

weather.gov/losangeles

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