518
FXUS66 KLOX 011632
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
932 AM PDT Mon Jul 1 2024

.SYNOPSIS...01/922 AM.

A significant heatwave will impact a large part of the area this
week and continue into next weekend. Temperatures will become
dangerously hot across much of the area. High temperatures by mid
to late week are expected to reach 95 to 105 degrees in many areas
away from the coast, with highs upwards of 105 to 115 over
interior valleys and foothills including the Antelope Valley.
Also, by late week, very warm to hot conditions could extend
closer to the coast. Patchy night and morning dense fog will be
possible near the coast early this week.

&&

.SHORT TERM (TDY-WED)...01/244 AM.

The marine layer is 900 ft deep but is slowly rising as an eddy
spins and lifts the marine layer. By dawn low clouds should cover
almost all of the coasts and will extend into a few vlys notably
the San Gabriel and eastern San fernando. A weak trof will pass
over the area today will will further lift the clouds. Low clouds
will slowly dissipate this morning but with an 8 mb onshore push
to the east in the afternoon it is likely that a few west facing
beaches will not clear. The lower hgts from the trof and the
deeper marine layer will team up to knock 2 to 4 degrees off the
max temps. The coastal areas will end up a few degrees blo normal
while the rest of the area will see near normal temps.

After today the forecast will be all about the heat. The heat wave
will start Tuesday as a large and warm E Pac high begins to nose
into the state from the west. There will be marine layer clouds
across the coasts in the morning but there will be weaker onshore
flow so clearing should be a little faster and more beaches will
see sunshine. Max temps will rise 1 to 2 degrees across the coasts
and vlys except for the Central Coast where even weaker onshore
flow will allow for a 3 to 5 degree warm up.

The warm up will begin in earnest on Wednesday as the upper high
pushes further into the state and hgts rise to 595 dam over LA
county and 596 dam over the Central Coast. At the same time the
onshore flow will lessen which will lead to a later arriving and
weaker sea breeze. The marine layer will be squashed to under 1000
feet and likely lower to near 600 ft. This will lead to low clouds
only covering the near shore area in the morning. The capping
inversion will be very strong and this may prevent some beaches
from clearing. Max temps will rocket up 5 to 10 degrees
everywhere. There will many 80 degree reading across the interior
coast, lots of 90s and some 100 to 101 degree readings in the
vlys. The interior and lower mtn elevations will see max temps
ranging from 102 to 106 degrees. The Antelope Vly will have
dangerous heat with highs of 108 to 112 degrees.

The Excessive Heat Warning for interior areas starts on Tuesday
which may be a day early and the day shift will have to consider
pushing the start date back a day. There is no doubt about the
need for Warnings across the interior on Wednesday. In addition to
the warnings, an Excessive Heat Watch has is also in effect from
the San Fernando Valley through the Santa Monicas, Calabasas, and
Agoura Hills, to the central Ventura County valleys and through
the Santa Ynez Range and Santa Lucia Range.

Overnight lows will have to monitored as the areas in the warmest
portion of the inversion (likely 800 to 1500 ft elevations) may
not see much cooling relief at all in the overnight hours.

n addition, gusty west to northwest winds are expected each
afternoon over most of the interior areas. The strongest gusts
(35-45 mph) will occur over the I-5 corridor and the western
Antelope Valley/foothills. These gusts will come in just under
wind advisories criteria.

.LONG TERM (THU-SUN)...01/302 AM.

The heat wave will persist through the xtnd period and into early
next week. The upper high will move directly atop of the state and
Srn CA will have hgts near 596 dam overhead through the entire
period. The sfc gradients weaken considerably on Fri and Saturday
and these will be the warmest two days with only a minimal amount
of marine layer clouds or marine layer influence.

Look for 2 to 4 degrees of warming each day Thu and Fri and just a
little cooling over the weekend. The Excessive Heat Warnings and
Watches will continue all the way through the weekend and into
early Monday morning, July 8 with max temps of 95-105 degrees in
many areas away from the coast, with highs upwards of 105-115 over
interior valleys and foothills including the Antelope Valley.

With max temps 10 to 20 degrees above normal, Major to Extreme
heat risk is likely through the weekend, especially Friday.

Overnight low temperatures will be well above normal in the
inversion zone with lows remaining above 80 degrees at some
locations over interior valleys and nearby foothills. These warm
lows will worsen the effects of extreme heat.

Even though they are not included in the watch the interior
coastal sections may well need Heat Advisories during the period
as the marine layer shrinks until it is too shallow to provide
much relief to the portion of the coast not in the near shore
area.

One last area of concern is the SBA south coast where Sundowners
are possible Thursday and Friday nights. Warming downsloping
sundowner winds could easily bring near 100 degree temperatures to
the SBA south coast including the city of SBA during the early
evening hours.

The combination of these very hot temperatures, areas of low
humidities and possible sundowner winds will lead to fire weather
risks. Please see the fire weather discussion below for all the
details.

&&

.AVIATION...01/1631Z.

At 1615Z at KLAX, the marine layer was 1600 feet deep. The top of
the inversion was at 2800 feet with a temperature of 24 Celsius.

For 18Z TAF package, high confidence in KPRB, KBUR, KVNY, KPMD and
KWJF TAFs as CAVU conditions are expected thru the period.

For 18Z Coastal TAFs, low to moderate confidence in current
forecast. Timing of return of CIG/VSBY restrictions could be +/- 4
hours of current forecasts.

KLAX...Moderate confidence in 18Z TAF. Timing of return of
CIG/VSBY restrictions could be +/- 3 hours of current 08Z
forecast. Also, there is a 40% chance of LIFR conditions 08Z-16Z.
No significant easterly wind component is expected.

KBUR...High confidence in 18Z TAF as CAVU conditions are
anticipated thru the period.

&&

.MARINE...01/702 AM.

For the Outer Waters, high confidence in current forecast. Today
through tonight, Small Craft Advisory (SCA) level winds will
continue. For Tuesday through Friday, winds and seas are expected
to remain below SCA levels. h 9 am this morning. For Tuesday
through Friday, high confidence in winds and seas remaining below
SCA levels.

For the Inner Waters north of Point Sal, moderate to high confidence
in current forecast. There is a 40-60% chance of SCA level winds
through this afternoon and evening. For Tuesday through Friday,
high confidence in winds and seas remaining below SCA levels.

For the Inner Waters south of Point Conception, high confidence in
current forecast. Today through Friday, winds and seas will remain
below SCA levels.

Patchy dense fog (with visibilities one nautical mile or less)
will continue to impact the coastal waters through the week. The
areal coverage of the dense fog will likely decrease each day.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning remains in effect from 11 AM Tuesday
      to 5 AM PDT Monday for zones 38-343>345-353-376>379-381>383. (See LAXNPWLOX).
     Excessive Heat Watch remains in effect from Wednesday morning
      through late Sunday night for zones
      88-342-348-351-352-356>358-369>375-380. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
      for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Cohen

weather.gov/losangeles

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