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000
FXUS66 KLOX 250030
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
530 PM PDT Tue May 24 2022

.SYNOPSIS...24/521 PM.

High pressure will bring warmer weather to areas away from the
coast through Wednesday. Closer to the coast, a persistent marine
layer will continue to affect the coastal areas expanding into the
coastal valleys late in the week. A cooling trend is expected for
late week as onshore flow strengthens. Gusty onshore winds are
expected each afternoon and evening for the mountains and interior
valleys. A warming trend is possible early next week.

&&

.SHORT TERM (TDY-FRI)...24/221 PM.

Today begins with the typical marine layer clouds and fog,
extending from the Santa Ynez Valley through the Santa Barbara
South Coast to the LA Basin, as depicted by satellite imagery.
Expecting the valleys to clear out nicely this morning, but clouds
will likely cling to the coasts into the early afternoon hours,
especially for the Santa Barbara south coast and Ventura County
Coast. There will be a significant disparity in temperatures
between the coasts enshrouded in clouds and sunny interior areas.
The Antelope Valley and interior San Luis Obispo will warm to the
upper 90s to near 100 degrees today, with highs stuck in the 60s
at the coast. Expecting a similar marine layer pattern tonight,
but overall flow is more southerly so we may see more clouds
banked up against south-facing slopes.

Onshore flow increases Wednesday, with the LAX-DAG onshore
gradient peaking around 6 to 7 mb in the afternoon hours. There
will also be a southerly component to winds, with the onshore LAX-
BFL gradient reaching 6 mb. Gusty west to southwest winds will
develop over the Antelope Valley in the afternoon, but should
remain below advisory levels. Still seeing hot temperatures in the
90s for the Antelope Valley and interior San Luis Obispo County,
but this additional onshore push should limit heating up north.
Otherwise, temperatures will be quite similar to today`s values,
as marine layer clouds and onshore flow will severely limit
warming at the coasts.

Thursday, onshore flow will peak with the LAX-DAG onshore
gradient peaking around 8 to 9 mb and the onshore LAX-BFL
gradient peaking at 7 mb. This will support potentially advisory
level gusty winds for the Antelope Valley and Santa Ynez Valley.
Clouds and fog should push deeper into the valleys thanks to the
increased onshore flow.

Overall the forecast looked on track, but reduced clouds over the
waters this afternoon and expanded the area of clouds and fog to
include Burbank and Van Nuys tonight.



***From Previous Discussion***

At the coast, May Gray will likely be the story for the remainder
of the week. Hourly forecast guidance hints at KOXR and KSBA
struggling to clear this afternoon in temperature/dewpoint
spreads, which agrees well with the EPS ensemble member for these
sites. EPS member solutions keep a significant amount of cloud
coverage in for the next several days along the Ventura County
coast and Santa Barbara South Coast as onshore flow strengthens.

A significant onshore push is progged to develop between Wednesday
and Thursday. Surface pressure gradients show between 2 and 3 mb
onshore trends during the period with KSBA-KBFL surface pressure
gradients tightening to greater than 7 mb onshore and KLAX-KDAG
approaching 10 mb onshore on Thursday. Deterministic NAM-WRF
solutions give decent onshore winds across the interior valleys
to at least bring a breezy afternoons for most interior locals.
There is a chance that these winds could push close to advisory
levels on Wednesday and Thursday. EPS ensemble member means bring
winds gusts into the 30-35 mph range for Thursday for KPMD and
KWJF, but local knowledge suggests that winds will likely
approach advisory level gusts in the foothills of the Antelope
Valley. Winds gusts up to 45 mph are advertised for now in the
forecast as there are plenty more solution periods to resolve the
winds and get a better idea for a wind advisory timing and
strength for Thursday.

With strong onshore flow developing for Thursday, cloud coverage
was trended more pessimistic for Thursday as local studies
suggest clouds likely lingering across the South Coast Basin.
Partly to mostly cloudy skies are in place for now, but if 10 mb
onshore pressure gradients do develop, the Los Angeles Basin will
very likely be mostly cloudy for the day and much cooler.

.LONG TERM (SAT-TUE)...24/1130 AM.

Ensemble guidance shows good agreement from Friday through Monday
as upper level flow shifts to the west/northwest, and gradually
strengthens over the timeframe. Both the GFS and EC agree on a
trough passage by late Monday, but there is more uncertainty in
temperatures for the extended period. Currently going with a
middle of the road solution for now, with the potential for
warming early next week.

Friday, strong onshore flow continues, primarily from the west
with an LAX-DAG gradient around 7 to 8 mb. Heights trend lower,
which will support a deep morning marine layer to push far into
the valleys and the coastal slopes. Heights fall more
significantly on Saturday, so again expecting a very deep marine
layer that may try to spill over into the Antelope Valley. There
is the potential for gusty winds Friday and Saturday due to the
stronger onshore push. Onshore flow is forecast to weaken Monday,
and will gain more of a northerly component.

&&

.AVIATION...25/0016Z.

At 2255Z at KLAX, the marine layer was 1200 feet deep. The
inversion top as at 3300 feet and 26 degrees Celsius.

Overall moderate confidence in the 00Z TAFs, except low confidence
in the LA Valley sites. For the coastal sites, the onset of low
clouds and flight restrictions could differ by +/- 2 hours from
TAF times. For the Central Coast, IFR conditions are expected with
a chance of LIFR at KSMX. Further south, IFR to MVFR conditions
are expected, although the timing of flight category changes is
lower confidence. There is a 40 percent chance that KVNY and KBUR
will remain VFR through the period.

KLAX...Moderate confidence in the 00Z TAF. MVFR cigs expected to
arrive by 02Z, but the timing could differ by 1-2 hours. There is
a 30% chance of IFR cigs initially, then lifting to MVFR. High
confidence in and east winds staying under 8 knots.

KBUR...Low confidence in the 00Z TAF. There is a 40 percent
chance of VFR conditions through the period.

&&

.MARINE...24/126 PM.

Light and broad southerly flow will continue across the coastal
waters into early Friday. By Friday night, gusty northwest winds
along with short period wind waves and rough seas will make their
return, especially in the outer waters.

Southerly winds will gradually expand through Thursday,
eventually pushing up to Monterey County and shove the seasonal
coastal jet well offshore. Local south to southeast winds of 10-15
knots are likely near all coasts in the morning hours, especially
Wednesday. More significantly, seas will fall to nearly lake-like
conditions by Thursday, with only 2-4 feet (locally 1 foot) total
waves everywhere including the Central Coast. The coastal jet
should reform quickly Thursday Night into Friday, with Gale Force
(focused outer waters to Central Coast) and widespread choppy seas
returning for the weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...Phillips/Hall
AVIATION...Smith
MARINE...Sweet/Kittell
SYNOPSIS...Hall/Smith

weather.gov/losangeles

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