993
FXUS66 KLOX 261832
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1132 AM PDT Thu Sep 26 2024

.SYNOPSIS...26/910 AM.

A warming trend will develop inland through Friday as high
pressure to the east nudges into the region. Closer to the coast,
onshore flow will keep a persistent marine layer and stronger sea
breeze in place with little to no warming. Night through morning
low clouds and fog will struggle to clear through the weekend.
Significant warming trend is on tap for early next week as high
pressure to the east builds in again.

&&

.SHORT TERM (TDY-SAT)...26/915 AM.

***UPDATE***

Marine layer depth remains the same as the last few days, around
1700 feet in LA County sloping to around 1000 feet along the
Central Coast. Stratus did not reach the LA/Ventura valleys this
morning, likely due to the significant clearing that occurred
Wednesday. With earlier sunshine temps may warm slightly across
the valleys but should still top out in the mid 80s to low 90s,
which is within a degree or two of normal. Otherwise, a lot more
of the same weather most areas today and through the weekend with
plenty of morning marine layer that will clear to near the coast
by afternoon.

***From Previous Discussion***

A warmer day looks on tap for today and Friday away from the
coast and outside the marine influence. 500 mb heights climb over
the region today and Friday, despite onshore pressure gradients
slightly strengthening through Saturday. A more June- like pattern
is looking to set up with stronger onshore flow and rising
heights over the coming days. Clouds will likely struggle to clear
away from the coast the next several days as high pressure will
likely tighten the marine inversion, decrease mixing at the top of
the marine layer, and delay clearing.

The trough to the southwest will advance back to near Point
Conception by Saturday night. Onshore pressure gradients trend
more strongly onshore for Saturday and some cooling should
develop. The beaches and immediate coastal locales will likely
continue to be shrouded in clouds.

.LONG TERM (SUN-WED)...26/427 AM.

The cut-off trough will play around with the area for the
extended period, moving over southern and central California for
the weekend, but then pulling back offshore for next week. 500 mb
heights increase between Sunday and Tuesday and temperatures will
likely warm well above normal between Monday and Tuesday.
Temperatures break away from NBM values during this period to
emphasize a hot weather pattern developing. Heat headlines may be
needed across portions of the area between Monday and Tuesday as
the air mass warms and temperatures rise to between 15 and 20
degrees above normal for this time of year.

While not certain, pattern recognition in the deterministic
solutions would suggest a non-zero chance of afternoon and
evening showers and thunderstorms between Tuesday and Wednesday.
A longer duration of southeast flow aloft develops with the
trough retrograding offshore, and this could bring some sub-
tropical moisture northward into the region from the remnants of
Tropical Cyclone John. A few members of the GEFS and EPS pick up
on the possibility of convection developing, but even more members
picked up precipitable water values climbing for late in the
period. The forecast ensembles suggest there is a 20 percent
chance of precipitable waters value climbing above 1 inch at KLAX
on Tuesday afternoon, which is more than ample for afternoon and
evening convective showers.

There is still quite a bit of spread, but forecast ensembles are
starting to suggest cooling for Wednesday and next Thursday.

&&

.AVIATION...26/1830Z.

At 1738Z at KLAX, the marine layer was 1500 ft deep. The top of
the inversion was 3900 ft with a temperature of 23 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 15%
chance of IFR conds at KBUR and KVNY 09Z-16Z.

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.

For KSBP and KSMX, there is a 30% chance of VLIFR conds 03-16Z.

For KSBA, there is a 10% chance of VLIFR conds overnight, and a
30% chance of IFR cigs at worst.

For KOXR and KCMA, there is a 30% chance of cigs as early as 03Z,
and LIFR conds 08Z-15Z.

For KSMO, KLAX, and KLGB, Cigs could return as early as 03Z or as
late as 08Z. There is a 20% chance of LIFR conds 08Z-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%
chance of 2SM BR and BKN004 conds between 08Z-15Z. Good confidence
any significant east wind component will remain under 6 kt.

KBUR...Moderate to high confidence in TAF. There is a 15% chance
of 3SM BR and BKN005-BKN008 cigs 09Z-16Z.

&&

.MARINE...26/911 AM.

In the outer waters, low to moderate confidence in the forecast
thru Fri eve. While there may be local advisory level gusts during
the afternoon/eve hours today and Fri, winds are expected to
mostly remain below Small Craft Advisory (SCA) thru Fri night.
However, there is a 40% chance that SCA level gusts will become
widespread enough to require an advisory, especially around Pt.
Conception. From Sat thru Mon night, moderate confidence in winds
remaining below SCA levels. There is a 20% chance of SCA winds
Sat afternoon through Mon, mainly around Point Conception. There
is a 30% chance of SCA level seas late Sat thru Mon, with the
highest chance across the northern areas.

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 this morning, and again tonight/Fri morning, with
the highest chances off the Central Coast.

&&

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

&&

$$

PUBLIC...MW/Hall
AVIATION...Lund
MARINE...DB/Lund
SYNOPSIS...MW

weather.gov/losangeles

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