293
FXUS66 KLOX 191155
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
455 AM PDT Fri Jul 19 2024

.SYNOPSIS...19/256 AM.

A significant heatwave will impact Southern California Friday
into next week. A large portion of the mountains, foothills, and
valleys away from the coast will experience dangerously hot
conditions, and very warm temperatures may extend toward the
coast. Gusty Sundowner winds will affect portions of southern
Santa Barbara County through Saturday night. Monsoonal moisture
will potentially bring thunderstorms to the interior mountains and
valleys each afternoon through at least Wednesday.

&&

.SHORT TERM (TDY-SUN)...19/410 AM.

A ridge of high pressure will continue to elongate over the
western states into next week, resulting in very warm to
dangerously high temperatures away from the coast through much of
next week. Slight changes are expected each day, but the message
remains the same - it will be very hot away from the coast and
heat illness is a threat to anyone, especially as you move further
inland (and especially further inland past the mountains).
Excessive Heat Warnings and Heat Advisories remain in place for
the majority of the mountains, valleys, and far interior areas
which will last through at least the weekend. The immediate
coastal areas (especially south of Point Conception) may see
limited change each day as a shallow marine layer each day will
remain present.

Today, temperatures will increase a few degrees across the
majority of the region due to the increasing 500 mb heights along
with a slight decrease in onshore trends. Saturday is a little
more difficult as the onshore trends start to increase slightly,
and a weak low pressure system moves over the Central Coast and
breaks down in the evening. This low pressure system may result in
a few degrees of cooling along the Central Coast areas closest to
the Coast. By Sunday, temperatures should climb to 105 to 112
degrees across the lower mountains and far interior areas
(including the Antelope Valley), 95 to 105 across the warmest
coastal valleys, while areas closest to the coast will range in
the upper 60s to high 70s degrees. These temperatures will
increase to 5 to 15 degrees above normal as you move away from the
coast.

The ridge of high pressure will continue to bring in moisture
from the south, increasing PWATs to 1.0 inches across Los Angeles
County by Saturday. As a result, there is a less than 20 percent
chance of thunderstorms (including dry lightning) and monsoonal
rain showers to the Los Angeles County interior mountains and
deserts (thanks to orographic lifting) each day in the short term,
especially during the afternoon and early evening hours. Saturday
looks to have the highest chances for thunderstorms this weekend,
as the PWATs peak that day for the weekend. However, these
chances remain too low to include in the official forecast.

As for winds, the Western Santa Ynez Range and Southwestern Santa
Barbara Coast will see gusty NW Sundowner winds each evening
through Sunday night. Tonight and Sunday evening look fairly
similar with the SBA to SMX pressure gradient sitting around -2
mb, which will bring gusts of 40 mph to locally 45 mph both
evenings. On Saturday evening, the pressure gradient is forecast
to strengthen to around -3.3 mb, which could cause a slight
increase in the gusts and result in a wind advisory being needed
for that evening and night. On Saturday, southerly flow from the
low pressure system and the ridge will lead to an increase in
southwesterly winds across interior mountains and valleys each
afternoon and evening Saturday and Sunday, however will likely
remain below advisory levels.

.LONG TERM (MON-THU)...19/417 AM.

The long-duration dangerously hot conditions will continue
through at least Wednesday, at least for the interior mountains
and far interior areas. Temperatures will remain fairly similar
day-to-day Monday through Wednesday as not much will change
synoptically. Nights will remain very warm across the far
interior, with forecast lows to be in the 70s to 80s, resulting in
little overnight relief and potentially worsen heat impacts. On
Thursday, a trough should drop down the west coast and
temperatures should drop for the later portion of the week.

The potential for daily monsoonal thunderstorms and locally heavy
showers continues into mid-week. PWATs will rise to around 1 to
1.5 inches across the region, thanks to the southerly flow
funneling the moisture northward. While the moisture continues to
increase and expand across the area, confidence remains low this
far out so thunderstorms remain out of the official forecast.
However, a slight chance of showers nudged into the eastern
Antelope Valley and eastern foothills, as well as the eastern San
Gabriel Mountains for Tuesday and Wednesday morning. If thunderstorms
were to form, they will likely form over the higher terrain and
interior valleys of Los Angeles and Ventura Counties and possibly
extend into Santa Barbara County by early next week.

&&

.AVIATION...19/1154Z.

At 08Z at KLAX, the marine layer was 1200 feet deep. The top of
the inversion was at 3400 feet with a temperature of 28 Celsius.

High confidence in TAFs for desert and valley TAFs.

Low confidence in all coastal TAFs. Cigs may vary frequently
through this morning for KSMO, KLAX, and KLGB, as mid-level
moisture disturbs marine layer clouds. Timing of the return of
cigs tonight may be off by +/- 3 hours.

KLAX...Low confidence in TAF. Cigs are expected to clear by 18Z,
and the timing of the return of cigs tonight may be off by +/- 3
hours. No significant east wind component expected.

KBUR...High confidence in TAF.

&&

.MARINE...19/334 AM.

For the outer waters, Small Craft Advisory (SCA) northwest winds
are ongoing and are expected to continue through this weekend.
There is a 70% chance of low end Gale Force winds to impact the
outer waters this weekend. A Gale watch is in effect from
Saturday afternoon through Sunday night. Winds will likely taper
off Monday, but there is a 50% chance of SCA winds Monday through
early next week. Steep seas will also impact the outer waters
through at least Monday.

For the inner waters north of Pt. Sal, northwest winds are
expected to reach SCA levels this afternoon and continuing into
Sunday night. The strongest winds are expected during the later
afternoon and evening hours each day. There is a 30% chance that
SCA winds don`t occur today, but they are much more likely
Saturday and Sunday (70%). Steep and hazardous seas are expected
this afternoon into the weekend.

For the inner waters south of Pt. Conception, winds will increase
this afternoon through this weekend in the Santa Barbara Channel.
SCA level winds expected this afternoon through Sunday evening for
the SBA Channel, strongest for the western portion. There is a
30% chance that winds will remain below SCA level in the Santa
Barbara Channel this afternoon/evening. SCA winds are far more
likely Saturday and Sunday (60%).

In the furthest southern inner waters, there is a 30% chance for
SCA northwest winds to occur over the waters off of the Los
Angeles and Orange County coasts Saturday and Sunday. The highest
chances are during the afternoon and evening hours across the San
Pedro Channel, and west of Catalina Island.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning remains in effect from 10 AM this
      morning to 10 PM PDT Wednesday for zones
      38-88-344-345-351>353-371-372-376>383. (See LAXNPWLOX).
     Heat Advisory remains in effect from 10 AM this morning to 10
      AM PDT Sunday for zones 342-343-369-370-374-375. (See LAXNPWLOX).
     Excessive Heat Watch remains in effect from Sunday morning
      through Wednesday evening for zones 342-343-369-370-374-375. (See LAXNPWLOX).
     Heat Advisory remains in effect from 10 AM this morning to 9
      PM PDT Saturday for zones 373-548. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 2 PM this afternoon to 11
      PM PDT Sunday for zones 645-650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 2 PM PDT Saturday for
      zones 670-673-676. (See LAXMWWLOX).
     Gale Watch in effect from Saturday afternoon through Sunday
      evening for zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Lund
AVIATION...Schoenfeld
MARINE...Lewis/Schoenfeld
SYNOPSIS...Smith

weather.gov/losangeles

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