480
FXUS66 KLOX 150453
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
953 PM PDT Tue May 14 2024

.SYNOPSIS...14/834 PM.

Consistent weather expected for the next few days. Coastal areas
will continue to see low clouds and below normal temperatures. In
contrast, temperatures will be above normal for interior areas,
with gusty winds at times, especially across the Antelope Valley.
A slight chance of showers will persist for the mountains each
afternoon through Wednesday.

&&

.SHORT TERM (TDY-FRI)...14/914 PM.

***UPDATE***

The weak upper low is slowly moving east and is expected to exit
the region late tomorrow. With little change to the overall
pattern, except for slight increases in the onshore gradient,
marine layer clouds are expected to again extend far inland
overnight. Clouds will be slow to retreat on Wednesday, with some
coasts seeing little to no clearing. Additionally, temperatures
will be similar to what was observed today. Highs will generally
be in the 60s for coasts, mid- to- upper 70s for valleys, and
around 90 for the deserts. If coastal areas such as Santa Barbara
City were to see more significant clearing than expected,
temperatures have the potential to be up to 5 degrees warmer than
forecast.

Vorticity from the weak upper level low will again yield a 10-20%
chance of showers/thunderstorms for the mountains and Antelope
Valley tomorrow afternoon. Additionally the low may cause lifting
of the marine layer, and produce overnight drizzle in some areas.
Drizzle is most likely for coastal areas of Ventura and Santa
Barbara counties.

No significant changes to the forecast, expect for slight
temperature adjustments to trend tomorrow`s highs towards
persistence, and extending the chance of afternoon showers into
the Antelope Valley (based on the latest HREF guidance).

***From Previous Discussion***

Very little change on tap through at least Friday. A weak upper
level low will slowly depart the area through late Wednesday,
with weak ridging by Friday. This will bring some steady warming
to the interior mountains and valleys, with temperatures 5 to 10
degrees above normal by Friday. On the coastal side of the
mountains however, this upper level change should have little
affect. While increasing high pressure aloft tends to lower and
shrink the marine layer, onshore pressure gradients will be
strengthening some at the same time which has the opposite affect.
While the marine layer depth and coverage will unlikely be exactly
the same each day, these two factors and the latest stagnant low
level humidity projections all suggest that any changes will be
small. As a result, temperatures will remain 5 to 10 degrees below
normal on the coastal side of the ranges, with any day-to-day
changes owing to the random fluctuations of earlier or later low
cloud clearing times.

Onshore wind gusts will increase and expand over the interior
areas as they have been each day, with gusts of 20 to 35 mph
common (strongest in the Antelope Valley with local gusts to 40
mph possible). Winds could be 5 mph or so stronger Thursday and
Friday with the stronger onshore pressure gradients, which may
push us into the low-end Wind Advisory category for the Antelope
Valley. Elsewhere, winds will be fairly seasonal.

The upper level low will also weakly destabilize the atmosphere
through Wednesday. While the moisture aloft is the main limiting
factor, there is a little (850mb dewpoints around 8 degrees
Celsius). In addition, the convective clouds and moisture
currently over southern Nevada and northwest Arizona will move
over our area later tonight into Wednesday morning. These clouds
could inhibit the convective potential some tomorrow, but if they
thin out in the afternoon like the computer models suggest, then
this could instead provide an extra moisture boost to the
convection potential. As a result, while still unlikely, there is
a 20 percent of showers for the typical shower magnets in the San
Gabriel Mountains and north Ventura Mountains. While not
explicitly in the forecast, there is also a 10 percent chance that
any shower grows into a thunderstorm. Lastly, while a very small
but non-zero chance, cannot completely discount a few drops or an
isolated shower over valley areas Wednesday morning and afternoon.
This is due to the clouds previously mentioned, as well easterly
steering flow capable of pushing any showers off the mountains.

.LONG TERM (SAT-TUE)...14/117 PM.

A series of small but potent low pressure systems will push
through the Pacific Northwest over the weekend. This will break
down the ridging aloft from Friday over the southwest. Another
weak upper level low will form 800 miles west of Los Angeles by
Thursday and remain parked through Friday. The systems to the
north will also draw this low closer to the coast, with a fairly
large spread in the ensemble solutions in terms of how fast and
how far west it progresses. By Monday or Tuesday, most solutions
have the low swinging through the area, with ridging aloft
reforming towards the middle of next week. These trends should
deepen the marine layer over the weekend, peaking Sunday and
Monday when areas of drizzle looks favorable. Cooler conditions
are expected as a result. Coastal areas, being cool already, will
not notice the change too much. Interior areas however will go
from 5-10 degrees above normal on Friday, to below normal by
Monday.

&&

.AVIATION...14/1637Z.

At 1630Z at KLAX, the marine layer was 2700 feet deep. The
top of the inversion was around 3600 feet with a temperature
of 17 degrees Celsius.

Overall for the 18Z TAF package, high confidence in desert TAFs
and moderate confidence in coastal/valley TAFs. Lower confidence
for coastal/valley sites due to uncertainties with timing of
dissipation and formation of stratus.

KLAX...Moderate confidence in 18Z TAF. There is a 20-30% chance
that MVFR CIGs will not dissipate this afternoon. Timing of flight
category changes could be +/- 2 hours of current forecast. No
significant easterly wind component is expected.

KBUR...Moderate confidence in 18Z TAF. Dissipation of MVFR CIGs
could be as late as 21Z. Return of MVFR CIGs could be +/- 2 hours
of current 06Z forecast. Also, there is a 30% chance of IFR CIGs
08Z-14Z.

&&

.MARINE...14/807 PM.

For the Outer Waters, moderate to high confidence in current
forecast. Through Thursday, high confidence in winds and seas
remaining below Small Craft Advisory (SCA) levels. For Thursday
night, there is a 30-40% chance of SCA level winds around Point
Conception. For Friday through Sunday, high confidence in winds
and seas remaining below SCA levels.

For the Inner Waters north of Point Sal, high confidence in
current forecast. Tonight through Sunday, winds and seas will
remain below SCA levels.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. For most of the southern Inner
Waters, winds and waves will remain below SCA levels through
Sunday. The only exception is the western half of the Santa
Barbara Channel where there is a 30-40% chance of SCA level winds
late Thursday afternoon and evening.

&&

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

&&

$$

PUBLIC...Kittell/Schoenfeld/Smith
AVIATION...RAT
MARINE...RAT/smith
SYNOPSIS...Schoenfeld

weather.gov/losangeles

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