988
FXUS66 KLOX 040651
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1151 PM PDT Thu Oct 3 2024

.SYNOPSIS...03/924 PM.

High pressure aloft will weaken some tonight, bringing slight
cooling to the area on Friday, then another warming trend will
develop over the weekend. Skies will be clear through the period
except for night through morning low clouds and fog along the
coast. Fog may be dense at times over the weekend.

&&

.SHORT TERM (THU-SUN)...03/938 PM.

***UPDATE***

Low clouds and fog are rapidly moving onshore and into most
coastal areas south of Pt Conception this evening following a 2mb
onshore trend and some cooling aloft as well. Tops are around
1100` this evening in the LA Basin sloping down to around 500`
along the Central Coast. Currently the forecast is for clear skies
in the valleys but given the rapid advancement this evening can`t
completely rule out some clouds sneaking into the valleys
overnight.

With the deeper marine layer and onshore flow Friday will
certainly be a cooler day everywhere, but especially the valleys
which were well into the 90s and lower 100s Thursday and likely
cooler by 3-6 degrees Friday. All heat advisories and warnings
have expired. There is still an Excessive heat watch in effect
this weekend into Monday, though based on the latest ensemble
based temperature guidance this next heat wave will not be as warm
and likely will be best handled with heat advisories.

***From Previous Discussion***

Moving into Friday, winds are forecast to shift from southeast to
southwest helping to cool most of the area 5-9 degrees. Warming
will start again Saturday as high pressure builds in again and
offshore flow returns again. The biggest uncertainty in the
forecast Saturday will be how extensive marine layer clouds will
be, so lower confidence in the temperatures at the coast. However,
considering how prominent stratus was for our last heat wave,
temperatures were trended towards the cooler solution at the
coasts. The current excessive heat warning is still in effect
starting Saturday, and will wait for the existing heat products to
end before making any further modifications.

.LONG TERM (MON-THU)...03/322 PM.

The area remains sandwiched between high pressure over New Mexico
and the strong, persistent low cycling just south of Alaska from
Sunday into next week, leading to some interesting features moving
through the region. A weak disturbance passes through from the
southwest Sunday and a weak upper level low moves into the region
Monday, transitioning to a cutoff low Tuesday. The impacts of
this low are somewhat uncertain, but it should help increase
marine layer clouds over the region and may lead to light drizzle
in the marine layer through Wednesday.

Temperatures are expected to peak Sunday with ongoing light
offshore winds. Highs should range from the upper 90s to low 100s
over the interior and warmer valleys. There will be some
northeast flow across the Santa Lucias which will likely bring a
return of 90-100 degree temperatures to the San Luis Obispo area.
There is some uncertainty in how much coastal clouds will
moderate temperatures Sunday and Monday,but leaning the forecast
towards cooler values at the coast. Heights start to fall Monday
(587-585 dam) starting the cooling trend that should last through
mid- week, in line with the weak low moving into the area. Max
temps will fall 6 to 12 degrees Tue and 2 to 4 degrees on
Wednesday. By Wednesday most of the coasts and some of the vlys
will be below normal, but the warmer vlys and interior will remain
3 to 6 locally 8 degrees above normal.

&&

.AVIATION...04/0648Z.

Due to a data outage, current marine layer and inversion height
data is not available for KLAX.

High confidence in TAFs for KPRB, KWJF, and KPMD.

Moderate confidence in KBUR and KVNY. There is a 20% chance of no
cigs developing tonight.

Low confidence in remainder of TAFs. VSBY could vary between
categories from VLIFR to low IFR through the night. For areas
north of Pt Conception, the arrival time of low CIGs could differ
by +/- 2 hours from TAF times.

Low confidence in tomorrow evening.

KLAX...Low confidence in TAF. VSBY is likely to vary between
1/2 to 4SM throughout the night. The clearing of low clouds could
differ by +/- 90 minutes. There is a 20% chance of an east wind
component reaching 8 kts between 08Z-16Z Fri.

KBUR...Moderate confidence in TAF, with a 20% chance of no cigs
developing tonight. The arrival of cigs may be off by +/- 90
minutes.

&&

.MARINE...03/824 PM.

For the Outer Waters (along the Central Coast south to San Nicolas
Island), moderate to high confidence in the current forecast for
winds, but low confidence in seas. Through Saturday, high
confidence in winds remaining below SCA (Small Craft Advisory)
levels. For Monday through Tuesday, there is a 30-40% chance of
SCA level winds, especially in the late afternoon through evening
hours. As for seas, swell heights of 8-12 feet are being recorded
at local buoys along the Central Coast north of Point Conception,
while the models are depicting seas of 6-8 feet. Adjusted the
forecast to account for this, and indicated subsiding seas on
Friday, following the model trends.

For the Inner Waters north of Point Sal, moderate confidence in
current forecast. Through Sunday, high confidence in winds and
seas remaining below SCA levels. For the afternoon and evening
hours on Monday and Tuesday, there is a 40-50% chance of SCA level
winds. Seas were also adjusted up for these waters, to match with
the observations.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Generally high confidence in winds
and seas remaining below SCA levels through Monday. Local NW gusts
to 20 kt are possible during the afternoon and evening hours on
Sunday around Point Mugu and in the San Pedro Channel. Then,
Monday night there is a 20-30% SCA winds for the Santa Barbara
Channel.

A shallow marine layer will continue to generate some dense fog
across portions of the coastal waters the next couple of nights
and mornings. Visibilities of one nautical mile or less can be
expected.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Watch remains in effect from Saturday morning
      through Monday evening for zones
      38-88-342>345-351>353-356>358-369>376-378>380-548. (See LAXNPWLOX).
PZ...NONE.

&&

$$

PUBLIC...MW/Phillips
AVIATION...Schoenfeld/Black
MARINE...Lund/Schoenfeld/Black/Smith
SYNOPSIS...MW/Smith

weather.gov/losangeles

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