007
FXUS66 KLOX 070411
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
911 PM PDT Sat Jul 6 2024

.SYNOPSIS...06/214 PM.

A long-lasting and extreme heatwave will continue across the
region, and especially the interior, through much of next week.
There is a high risk for dangerous heat illness and fast-growing
fires. High temperatures will reach 105 to 115 across interior
valleys, mountains and deserts. Dense fog may develop across some
beaches during the night and morning hours.

&&

.SHORT TERM (SAT-TUE)...06/909 PM.

***UPDATE***

The marine layer has snapped back down to below 1000 feet thanks
to compressional effects of the strong ridge aloft. Any eddy
development tonight into Sunday morning should be much weaker than
we saw today as indicated in part by the Santa Barbara to San
Diego pressure gradient being much weaker this evening. At least
Have adjusted the low cloud forecast accordingly with low clouds
now anticipated to make it into coastal areas and perhaps sneaking
into a few lower coastal valleys. Patchy dense fog is possible
just about anywhere low clouds roll into tonight into Sunday
morning. Smoke from the Lake fire may increase the odds of dense
fog focused across the Central Coast with the potential for
reduced visibility from smoke in and near Santa Barbara County.

Tough temperature forecast tomorrow as model guidance shows
similar temperatures into tomorrow, but todays unusual boost in
marine layer influence due to a strong eddy is probably not being
fully captured. There will probably be a few degrees of cooling
for some interior areas in Sunday, but with record heat for those
areas today, it will still be plenty hot to maintain most of the
current excessive heat warnings. Lower confidence in the Santa
Clarita Valley and Santa Ynez range where cooling today was
greater than expected, but we may see a rebound for at least some
of these areas on Sunday. Have maintained current slate of heat
warnings (see NPWLOX for details) for now.

***From Previous Discussion***

Low clouds lingered early this afternoon for many coastal areas,
and there were areas of smoke coming off the Lake Fire in the SBA
County mtns. Otherwise, sunny skies covered the forecast area
with little change expected the rest of today.

The marine inversion has been low and strong today, but under the
inversion there has been a broad southerly flow over the SoCal
bight into VTU/L.A Counties. This along with a quickly increasing
onshore flow has brought cooler temps to the inland coast and
adjacent vlys early this afternoon. There has been enough cooling
that many of the Heat Advisories and Excessive Heat Warnings for
these areas have been cancelled. The same goes for the inland
Central coast to the Santa Ynez Vly. However, high heat has been
affecting the interior vlys to the mtns and deserts early this
afternoon with temperatures soaring into the 105 to 115 degree
range and Excessive Heat warnings continue there.

A 598 dam H5 upper level high over nrn CA early this afternoon
will slowly build S and into srn CA thru Mon. This upper level
high will keep very hot conditions continuing for the next several
days over the interior vlys to the mtns and deserts, where
Excessive Heat Warnings will continue. Please see the latest Non-
Precipitation Weather Message (LAXNPWLOX) for further details on
the current warnings.

For the coast and adjacent vlys, good onshore flow will keep
temps from getting excessively hot, but will still be several
degrees above normal. Pressure gradients will be quite strong
onshore Sun then turn slightly weaker for Mon. By Tue, pressure
gradients should be somewhat weaker and allow temps to warm up
again for the vlys, where Heat Advisories may be needed.

As far as cloud cover, varying amounts of night and morning low
clouds and fog will affect mainly the coast some inland
penetration to a few adjacent vlys. Patchy dense fog will also be
possible the next couple of nights along the Central Coast.
Otherwise and elsewhere, mostly clear skies can be expected,
except for areas of smoke from the Lake Fire in the short term
over portions of SLO/SBA Counties.

.LONG TERM (WED-SAT)...06/213 PM.

The GFS and EC are in generally good agreement in the extended
period. The large and strong upper level high will slowly push
into srn NV for Wed then linger in this general area into Thu. The
upper level hi will then move more into the Four Corners region
for Fri and Sat. Srn CA will be under the western and southwestern
periphery of the upper level hi thru Fri, then a weak upper level
trof will develop along the CA coast for Sat.

The Central Coast is expected to have night and morning low
clouds and fog thru the period, with varying amounts of low clouds
and fog S of Point Conception, primarily on the L.A./VTU County
coast at times as a northerly flow over the Santa Ynez range
should keep the SBA County S coast free of the low clouds. Low
clouds may persist at some of the Central Coast beaches each
afternoon as well. Otherwise, mostly clear skies are expected for
Wed thru Sat.

Excessive heat is expected to continue Wed and Thu, especially
for the interior vlys to the mtns and deserts, and existing
Excessive heat Warnings which run thru Wed for these areas may
need to be extended into Thu. It also looks like Heat Advisories
or even Excessive Heat Warnings may be needed for the vlys and
Santa Ynez Mtns Wed and Thu as temps heat up due to to weaker
onshore flow.

Temps should cool down enough for Fri and Sat due to stronger
onshore flow to the N and E that the only areas that may need heat
products would be the L.A. County mtns and deserts. Even with
cooler temps for the coast and vlys, it will still be several
degrees above normal each day.

&&

.AVIATION...07/0027Z.

At 18Z at KLAX, the marine layer was 900 feet deep. The top of
the inversion was at 4200 feet with a temperature of 35 deg C.

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

Moderate to Low confidence in all other coastal and coastal
valley sites. Flight category changes may be off by +/- 2 hours.
LIFR conditions possible starting after 02Z-08Z at KSMO (30%),
KLAX (30%), KLGB (20%). VLIFR conditions possible 08Z-14Z at KSBP
(10%), KSMX (30%), KSBA (20%), KOXR (20%), KCMA (10%), KBUR
(10%), and KVNY (10%) due to shallowing of the marine layer
overnight. Cigs/vsbys are likely (80-90%) to improve to MVFR-VFR
conditions 18-22Z. There is a chance that KLAX/KSMO (10-20%) and
KOXR/KSBA (30-50%) have limited to no clearing.

Nearby fires may lead to periods of MVFR/VFR smoke at terminal,
especially KSBA and north.

KLAX...Moderate to Low confidence in the 00Z TAF. Cig/vsby
arrival could be off by +/- 2 hours. Conditions should remain IFR
for most of the period, but there is a chance (30%) of LIFR
conditions likely after 06Z thru 12Z. MVFR to VFR conditions
expected after 17Z and should remain until late. A significant
east wind component is not expected thru the period.

KBUR...Moderate to Low confidence in the 12Z TAF. There is a 30%
chance that LIFR cigs/vsbys will arrive after 12Z. There is 10%
chance of VLIFR conditions for a short time after 12Z. Conditions
should improve to at least MVFR by 16Z.

&&

.MARINE...06/231 PM.

In the Outer Waters, Small Craft Advisory (SCA) level winds have
dropped below SCA levels in all areas.

For the most part, expect winds to remain below SCA levels
tonight and Sun morning, then close to but just below SCA levels
Sun afternoon thru Thu. There is a 30% chance of SCA level NW
winds in the far outer waters and from near Pt. Conception to NW
of San Nicolas Island during the late afternoon thru late evening
hours each day Sun thru Thu.

In the inner waters N of Pt. Sal, there is a 30% chance of SCA
level winds during the afternoon/evening hours Mon and Tue,
otherwise SCA conds are not expected thru Wed night.

In the inner waters south of Pt Conception, SCA conditions are
not expected thru Thu. However, there is a 30% chance of SCA
winds during the afternoon/evening hours Tue thru Thu in western
portions of the Santa Barbara Channel, mainly from Santa Cruz
Island to the SBA County south coast from Pt. Conception to
Gaviota to Refugio State Beach.

Areas of dense fog will continue to affect the coastal waters
through Sun morning. Please reference the Marine Weather
Statement for additional information.

&&

.BEACHES...06/233 PM.

A moderate southerly swell will affect the Southern California
coastal waters through Sunday, with a 15-17-second period this
weekend. While surf is not expected to be particularly high, surf
heights of up to 4 to 6 feet are anticipated at beaches exposed to
southerly swell, especially the LA and Ventura County beaches.

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 south-facing beaches of LA and
Ventura Counties. A Beach Hazards Statement is in effect through
Sunday evening to address these concerns.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning remains in effect until 9 PM PDT
      Wednesday for zones 38-343>345-353-376>379-381>383. (See LAXNPWLOX).
     Excessive Heat Warning remains in effect until 9 PM PDT
      Sunday for zones 88-351-352-375-380. (See LAXNPWLOX).
     Beach Hazards Statement in effect through Sunday evening for
      zones 354-362-366. (See LAXCFWLOX).
     Red Flag Warning in effect until 6 AM PDT Monday for zones
      378-381. (See LAXRFWLOX).
PZ...NONE.

&&

$$

PUBLIC...Munroe/Sirard
AVIATION...Lewis/DB
MARINE...DB
BEACHES...DB
SYNOPSIS...Sirard

weather.gov/losangeles

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