500
FXUS66 KLOX 042110
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
210 PM PDT Thu Jul 4 2024

.SYNOPSIS...04/101 PM.

A significant heatwave will affect the region this week and will
continue through much of next week, with dangerously hot
temperatures across much of the area. High temperatures will reach
95 to 105 degrees in many areas away from the coast, and upwards
of 105 to 115 across interior valleys and foothills, including
the Antelope Valley. Patchy night to morning dense fog will
develop near the coast through at least Friday morning.

&&

.SHORT TERM (TDY-SUN)...04/154 PM.

Interesting day today as the marine layer depth increased to
around 1500 feet south of Pt Conception and this combined with a
slight onshore trend to the east caused temperatures today to take
a significant dive, as much as 12 degrees cooler across some of
the coastal valleys. At elevations above 1500-2000 feet
temperatures were very hot. Antelope Valley highs will be around
110 as well as portions of interior SLO and SB Counties.

High res models continue to indicate significant warming in all
areas Friday, including the beaches as onshore flow weakens
considerably and a light northerly flow develops that will provide
an additional temperature boosting factor. Highs expected to jump
as much as 15-20 degrees above today`s levels for coastal areas,
with special emphasis along the Central Coast down to southern
Santa Barbara County where highs could reach near 100 away from
the immediate coast. Farther inland expecting temperatures
approaching 115. Forecast high for Woodland Hills is 111 Friday
but the latest ensemble projections show around a 10% chance of
reaching 115. Friday has perhaps the best chance to have
widespread broken records as the current records are reasonably
within reach in many areas.

Saturday will be another interesting day as models are showing
several degrees of cooling at lower elevations, especially south
of Pt Conception. Onshore flow is slightly weaker in the morning
but 3mb stronger to the north and east in the afternoon so a lot
will depend on how quickly the onshore trends kick in. Forecast
calls for 3-6 degrees of cooling most coast/valley areas Saturday.
This still falls squarely in the Excessive heat warning range for
valleys but just low end heat advisories for inland coastal
areas. Interior areas will not feel these effects so little if any
change or possibly even warmer there. Chances for broken records
Saturday are lower in many areas due to the cooling expected for
coast and some valleys and much higher record values due to a heat
wave in 2018.

Additional onshore trends expected Sunday leading to more cooling
for coastal areas and spreading farther inland. May have to re-
evaluate some inland coastal heat products on Sunday as
temperatures in the mid 70s to mid 80s would be below heat
advisory levels. Onshore flow will reach interior areas but with
temperatures still at or above 110 Excessive heat warnings there
will still be needed. The increase in onshore winds there in the
afternoon, particularly across the interior mountains and Antelope
Valley, will increase the fire risk in those areas.

.LONG TERM (MON-THU)...04/209 PM.

The overall pattern next week remains quite hot across the
interior and certainly well above normal closer to the coast.
After Sunday`s onshore flow increase, models have been pretty
consistent indicating lighter, though still present, onshore flow
the rest of next week. Meanwhile, the upper high really doesn`t
move or weaken very much. As a result, interior areas will
continue to scorch with highs near or above 110 and warmer
coastal valley highs will reach around 105 each day. Lower
confidence with coastal temperatures due to the uncertainty with
the marine layer and possible eddy development over the southern
coastal waters, but highs there should be at least 4-8 degrees
above normal all week.

&&

.AVIATION...04/1800Z.

At 17Z at KLAX, the marine layer was 1200 feet deep. The top of
the inversion was at 4100 feet with a temperature of 30 deg
Celsius.

High confidence in CAVU TAFs for KPRB, KSBP, KBUR, KVNY, KPMD,
and KWJF.

Low clouds and IFR conds should clear from the coastal airfields S
of Point Conception by 19Z. Expect somewhat less low cloud
coverage tonight, mainly affecting coastal sections of L.A. and
VTU Counties, and possibly the Central Coast. Conds will be mostly
LIFR to IFR, except for a 50% chance of VLIFR at KLAX and KLGB
late tonight and early Fri. From 04Z-09Z this evening, there may
be areas of MVFR vsbys due to smoke and haze from holiday
fireworks celebrations.

KLAX...Moderate confidence in the 18Z TAF. There is a 30% chance
that cigs will linger until 19Z. There is a 30% chance of MVFR
vsbys due to smoke and haze from 04Z-09Z. There is a 60% chance
that IFR cigs will move into the airfield this evening around
03Z-04Z. There is a 50% chance of VLIFR conds 11Z-15Z Fri.

KBUR...High confidence in the 18Z TAF with VFR conds thru the
period, except there is a 30% chance of MVFR vsbys due to smoke
and haze from 05Z-09Z.

&&

.MARINE...04/126 PM.

In the Outer Waters, Small Craft Advisory (SCA) level winds will
develop in the southern zones (PZZ673/PZZ676) this afternoon, with
SCA winds continuing into Saturday morning. In the northern zone
(PZZ670), there is a 30% chance of SCA winds this afternoon/eve,
with SCA level winds expected Fri afternoon thru late Fri night.
There is a 50% chance of SCA level NW winds Sat afternoon/eve.
SCA conds are not expected later Sat night thru Tue night.

For the Inner Waters north of Pt. Sal, SCA conditions are not
expected thru Tue night, except there is a 40%-50% chance of SCA
winds Fri afternoon/eve.

For the Inner Waters south of Pt. Conception, SCA winds are likely
during the late afternoon thru late night hours today and Fri in
western portions of the Santa Barbara Channel. The area with the
greatest threat of SCA level winds is from Santa Cruz Island to
the SBA County south coast from Pt. Conception to Gaviota to
Refugio State Beach. Otherwise, conds will be below SCA levels
for the southern inner waters through Tue night.

Areas of dense fog is expected to affect the coastal waters this
morning, and again tonight and Fri morning. Please reference the
Marine Weather Statement for additional information.

&&

.BEACHES...04/128 PM.

A southerly swell will affect the Southern California coastal
waters into Friday, followed by 15-17-second southerly swell
persisting into the weekend. While surf is not expected to be
particularly high, surf heights upwards of around 5 feet are
anticipated at beaches exposed to southerly swell -- especially
the LA and Ventura County beaches. Moreover, significant wave
energy with the long-period swell will combine with the elevated
surf to create dangerous conditions at area beaches, with powerful
and dangerous rip currents expected. This is especially the case
for the beaches of LA and Ventura Counties. A Beach Hazards
Statement is in effect from through the weekend to address these
concerns.

&&

.FIRE WEATHER...04/136 PM.

A dangerous fire weather scenario exists through Saturday. The
current heat wave is resulting in an unprecedented stretch of
extremely hot conditions with rapidly drying fuels. Humidities
over the interior areas will fall into the 5 to 10 percent range
by Friday with poor overnight recoveries. Coastal valley areas
will also see humidities drop into the teens by Friday. Meanwhile,
northwest to northeast winds will gust between 20 to 40 mph
through Friday Night over southern Santa Barbara County, many
mountains, and the interior valleys like the Antelope Valley.
While classic Red Flag thresholds will likely not be met,
considering the extreme nature of this event and the holiday fire
ignition sources available, conditions are favorable for critical
fire weather activity and behavior. That is why Red Flag Warnings
have been issued.

There is a high risk for grass fires and plume dominated
wildfires. The public needs to be urged to refrain with anything
that can start a fire, especially in open spaces with dry fuels.
Fireworks, campfires, firearms, and dragging tow chains have all
started destructive wildfires in the past. Consider the risk for
firefighters and neighbors if a fire starts. Residents near large
open spaces and the wild land interface should have a plan on
what they will do if a wildfire breaks out. Visit
readyforwildfire.org and wildfirerisk.org for good resources.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning remains in effect until 6 PM PDT
      Wednesday for zones 38-343>345-353-376>379-381>383. (See LAXNPWLOX).
     Excessive Heat Warning remains in effect until 6 PM PDT
      Monday for zones 88-342-348-351-352-356>358-369>375-380. (See LAXNPWLOX).
     Heat Advisory remains in effect until 6 PM PDT Sunday for
      zones 341-347-355-368-548. (See LAXNPWLOX).
     Excessive Heat Warning remains in effect until 6 PM PDT
      Saturday for zones 349-350. (See LAXNPWLOX).
     Beach Hazards Statement in effect through Sunday evening for
      zones 354-362-366. (See LAXCFWLOX).
     Red Flag Warning in effect from 10 AM Friday to 6 AM PDT
      Saturday for zones 342>345. (See LAXRFWLOX).
     Red Flag Warning in effect from 6 PM this evening to 6 AM PDT
      Saturday for zones 349-351>353-376>378-381. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect until 2 AM PDT Friday for zone
      650. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM Friday to 3 AM PDT
      Saturday for zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 AM PDT Saturday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW
AVIATION...Sirard
MARINE...Sirard
BEACHES...Cohen/Sirard
FIRE...Kittell
SYNOPSIS...MW/KL

weather.gov/losangeles

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