752
FXUS66 KLOX 270454
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
954 PM PDT Thu Sep 26 2024

.SYNOPSIS...26/119 PM.

A quiet weather pattern will continue through the weekend with
near to slightly below temperatures for coast and valleys and
above normal temperatures farther inland. Night and morning low
clouds and fog will continue near the coast and spread locally
into the valleys. Warmer weather is expected early next week.

&&

.SHORT TERM (THU-SUN)...26/951 PM.

***UPDATE***

Heat continues to grow over the interior, especially for northern
interior San Luis Obispo County which saw about 10 degrees of
warming today. In general, temperatures trended 2-5 degrees warmer
as marine layer clouds burned off earlier than yesterday. Despite
this warming, highs for the coasts and coastal valleys were still
about 5-10 degrees below normal, whereas the interior and deserts
were about 4-9 degrees above normal.

Friday, high pressure will build further over the region and
northeast winds over the interior should lead to temperatures
reaching the mid 90s to near 100 degrees. Marine layer clouds will
become more limited Friday with earlier clearing times. Highs
Friday look on track with 3-7 degrees of warming for the region
but things should shift to cooling as the closed low approaches
from the west.

The current forecast looks on track with only some minor changes
to the marine layer cloud forecast.

***From Previous Discussion***

A 1-2mb weakening of the onshore flow combined with earlier
clearing of the marine layer let to a few degrees of warming
today, mainly for coast and coastal valleys. A similar pattern is
expected for Friday as well as the upper low that has been
spinning just off the coast has drifted slightly farther west.

On Saturday most of the ensemble solutions swing the upper low
back to the area which should mean increasing marine layer
stratus, later clearing, and slightly cooler temperatures. Most of
those solutions linger the upper low into Sunday, but 10-20% of
the solutions show it moving east of the area by Sunday afternoon
and the latest forecast gradients also show some weakening of
onshore flow Sunday as well so possibly some earlier clearing and
a couple degrees of warming.

Otherwise, very low impact weather across southwest California
through the weekend with mostly light wind and temperatures
slightly below normal, except above normal across the Antelope
Valley, mountains, and interior SLO County.

.LONG TERM (MON-THU)...26/207 PM.

A warming trend is still expected early next week, but there
remains quite a bit of uncertainty with the magnitude and
duration. More recent ensemble solutions have been trending not
quite as hot. And even the latest GFS has backed off the heat
somewhat while onshore flow is around 2mb stronger than what it
was showing yesterday. Most of the projections still show Tuesday
being the warmest day but there`s also some uncertainty with that
as the GFS shows a 1-2mb onshore trend. Based on this guidance
the Tuesday temperatures have been lowered a few degrees, but
still getting into triple digits for the warmer valleys and close
to 90 across interior parts of the coastal plain, including
Downtown LA, and parts of the Central Coast.

The spread of model solutions past next Tuesday remains quite
large as models continue to struggle with this pesky upper low off
the coast. Most favor a modest cooling trend (3-6 degrees) for the
latter part of next week, while a smaller percentage show either
little change or even more significant cooling. There are a
handful of EPS solutions indicating a light to moderate Santa Ana
very late next week or next weekend.

&&

.AVIATION...27/0117Z.

At 0004Z at KLAX, the marine layer was 1100 ft deep. The top of
the inversion was 2400 ft with a temperature of 25 Celsius.

High confidence in desert TAFs.

Moderate to high confidence in KPRB, KBUR, and KVNY. There is a
20% chance of VLIFR- LIFR conds at KPRB 07-17Z. There is a 10-20%
chance of IFR conds at KBUR and KVNY 11Z-15Z.

Moderate confidence in remainder of TAFs through 03Z, then low
confidence. Timing of flight cat changes could be off by up to
+/- 3 hours and off by 1 flight cat. Better chance for earlier
arrivals north of Point Conception. For KSBP and KSMX, there is a
30% chance of VLIFR conds 05-16Z. For KSBA, there is a 10% chance
of VLIFR conds overnight.

For KOXR and coastal TAF sites south there is a 30% chance of
cigs as early as 03Z. LIFR conditions are possible for KLAX and
KLGB from 10Z-15Z.

KLAX...Moderate confidence through 03Z, then low confidence. Cigs
could arrive as early as 03Z or as late as 08Z. There is a 20-30%
chance of LIFR conds between 10Z-14Z. Good confidence any
significant east wind component will remain under 6 kt.

KBUR...Moderate to high confidence in TAF. There is a 10-20%
chance of brief LIFR to IFR cigs 12Z-15Z.

&&

.MARINE...26/904 PM.

Across the outer waters, there is low to moderate confidence in
the forecast. Localized Small Craft Advisory (SCA) winds are
occuring around Point Conception this evening, but at this time
are not expected to become widespread enough to warrant an
advisory. Friday afternoon there is a 40% chance of local SCA
gusts around Point Conception again, followed by a 20% chance
Friday through Monday. Elsewhere, there is a 30% chance of SCA
level seas late Sat thru Mon, with the highest chance across the
northern areas. Otherwise for the rest of the outer waters, SCA
conditions are not expected.

Across the inner waters north of Pt Sal, the Santa Barbara
Channel, and inner waters from Pt Mugu southward, moderate to high
confidence that winds and seas will remain below SCA levels thru
Mon night. There is a 20-30% chance of SCA level winds this
afternoon/eve, mainly in western and southern portions of the
Santa Barbara Channel, and from near Anacapa Island to Point Dume.

Patchy dense fog with visibilities of 1 NM or less may affect the
coastal waters tonight through Friday morning, with the highest
chances off the Central Coast.

&&

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

&&

$$

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

weather.gov/losangeles

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