059
FXUS66 KLOX 051801 AAA
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1101 AM PDT Fri Jul 5 2024

updated aviation discussion

.SYNOPSIS...05/957 AM.

A long-lasting and extreme heatwave will affect the region through
much of this week, with a high risk for dangerous heat illness and
fast-growing fires. Today will be the hottest in the coastal and
valley areas, with Saturday the hottest over the interior areas.
Peak high temperatures will reach 95 to 105 degrees in many areas
away from the coast, and upwards of 105 to 115 across valleys and
mountains. All-time records will be threatened. Dense fog will
affect the immediate coastal areas.

&&

.SHORT TERM (TDY-SUN)...05/1016 AM.

***UPDATE***

The long lasting and extreme heat wave continues. Today and
Saturday have all the ingredients to be the hottest and most
dangerous in terms of heat-illness and fire risk. PLEASE avoid
hiking in the mountains and the hills through this weekend and
stay away from anything that could spark a fire.

High pressure aloft is peaking around 595 dekameters. Onshore
pressure gradients will be near neutral for much of today. North-
to-south gradients continue to trend offshore, and it is this
gradient in particular that has behaved like this for nearly all
of our all-time record hot days. All systems are go for
widespread triple-digit heat inland of the coastal plains and
significantly hotter than yesterday. Several calendar day records
are sure to fall today, with a few all-time records threatened
today or Saturday (Lancaster, Palmdale, Paso Robles). The coastal
areas will be the hardest to predict, as the shallow marine layer
remains and is not showing any signs of going away. As a result,
the most likely outcome is for the beach areas to stay in the 70s
with a very sharp gradient going inland reaching 100 degree
temperatures within 5 to 10 miles of the ocean.

A few changes were made this morning. Added Palos Verdes to the
Heat Advisory as they will mostly in the hot layer above the
shallow marine layer. Lowered the temperatures along the immediate
coasts of southeast and northwest Santa Barbara County. It will
be very hot just a few miles inland, and rather warm at the
beaches, but steady onshore flow at the coast should keep the
moderating marine layer around. Also added a Wind Advisory for
southwest Santa Barbara County for tonight as the winds look
similar to the 40 to 50 mph gusts from last night. Will look into
the current end times for the Excessive Heat Warnings and Heat
Advisories. They all look good through Saturday, but the coastal
and valley areas may need to end a little earlier than their
currently scheduled end times.

***From Previous Discussion***

Well, today is the day - the hottest day of the prolonged period
of dangerously hot weather. Make sure to limit time outdoors in
the sun and stay hydrated to avoid any heat illness.

Some low clouds and fog were hanging out along the coasts early
this morning, though very patchy in nature. Onshore pressure
gradients between KLAX and KDAG were weakening, while N-S
gradients were becoming increasingly offshore. Therefore, the
marine layer clouds are expected to burn off rather quickly this
morning. Temps at 950 mb are expected to rise quite a bit today
due to all of this. This will allow for plenty of heating -up to
20 degrees compared to yesterday`s high temperatures, and 15 to 20
degrees above normal for this time of year. As a result, today
has the best chance for several locations to break daily high
temperature records.

Saturday`s maximum temperatures will be similar to today`s,
though a few degrees cooler at the coasts and coastal valleys due
to increasing onshore trends through the weekend. Exact
temperatures at the coastal locations on Saturday will depend on
when the increasing onshore trends start up, leading to less
confidence in the heat advisories for coastal areas on Saturday.
Even less confidence in the advisories on Sunday as temperatures
in the mid 70s to mid 80s would be below advisory criteria. While
the onshore flow will reach interior areas on Sunday,
temperatures will still be at or above 110 in the deserts and far
interior valleys of SLO County, and above 100 degrees in the
warmer locations in the L.A./VTU valleys. Therefore the Excessive
heat warnings will likely still be needed across those locations.
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)...05/440 AM.

Unsurprisingly, hot weather continues through the extended period
due to the high pressure aloft hanging out to the north and east
of the region. The onshore flow starts weakening again on
Monday resulting in a few degrees of warming both Monday and
Tuesday across the region, except the deserts and mountains which
will change little if at all due to the stationary high. Then,
conditions are expected to be very similar Tuesday through
Thursday. The deserts and far interior areas of SLO County 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 up to 4-8 degrees above normal
all week.

&&

.AVIATION...05/1800Z.

At 17Z at KLAX, the marine layer was 700 feet deep. The top of
the inversion was at 3300 feet with a temperature of 34 deg
C.

Moderate to hi confidence in the 18Z TAFs. Most airfields will be
VFR thru the fcst period. Low clouds should move back into
coastal airfields from KOXR southward at some time tonight and
persist into Sat morning, with IFR/MVFR conds. There is also a 30%
chance of LIFR conds at KSMX late tonight and early Sat. Timing
of the onset and any dissipation of the low clouds may be off +/-
an hour or two. There will also be some MVFR to even local IFR
vsbys early in the TAF period for the coast and vly airfields of
L.A. County due to haze. Some more haze is possible (50% chance)
late tonight into Sat morning for KBUR and KVNY with MVFR vsbys.

KLAX...Moderate confidence in the 18Z TAF. MVFR vsbys due to haze
should end around 20Z. Tonight, there is a 40% chance that IFR
cigs will arrive as early as 04Z. Cigs are expected to improve to
MVFR around 14Z. Timing of onset and dissipation of the low clouds
may be off +/- an hour or two. There is a 20% chance of an east
wind component of 7-8 kt from 10Z-17Z Sat.

KBUR...Moderate to high confidence in the 18Z TAF. VFR conds
should prevail for most of the fcst period. However, MVFR vsbys
in haze is expected until about 20Z and again tonight from about
09Z-15Z.

&&

.MARINE...05/821 AM.

In the Outer Waters, Small Craft Advisory (SCA) level winds will
continue in the southern zones (PZZ673/PZZ676) thru Sat morning.
In the northern zone (PZZ670), SCA conds are likely (70% chance)
this afternoon thru tonight. For the most part, expect winds to
remain below SCA levels Sat afternoon thru Tue night. However,
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,
especially during the late afternoon thru late evening hours.

For the Inner Waters N of Pt. Sal, SCA conds are likely (70% chance)
this afternoon/eve. There is a 30% chance of SCA level winds Sat
afternoon/eve. SCA conds are not expected Sat night thru Tue night.

For the Inner Waters south of Pt. Conception, there is a 30%
chance of SCA conds late this afternoon and evening 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. Otherwise, conds will be below SCA
levels for the southern inner waters thru Tue night.

Areas of dense fog will affect the coastal waters this morning.
Please reference the Marine Weather Statement for additional
information.

&&

.BEACHES...05/820 AM.

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 upwards of around 6 feet at times are anticipated at
beaches exposed to southerly swell -- especially the LA and
Ventura County beaches. The 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 the weekend to address these
concerns.

&&

.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 in effect until 6 PM PDT Sunday for zones
      341-347-355-367-368. (See LAXNPWLOX).
     Excessive Heat Warning remains in effect until 6 PM PDT
      Saturday for zones 349-350. (See LAXNPWLOX).
     Wind Advisory in effect from 6 PM this evening to 3 AM PDT
      Saturday for zones 349-351. (See LAXNPWLOX).
     Beach Hazards Statement in effect through Sunday evening for
      zones 354-362-366. (See LAXCFWLOX).
     Heat Advisory remains in effect until 6 PM PDT Sunday for
      zone 548. (See LAXNPWLOX).
     Red Flag Warning in effect until 6 AM PDT Saturday for zones
      342>345-349-351>353-376>378-381. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 9
      PM PDT this evening for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon 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...Lund/DB/Kittell
AVIATION...Sirard
MARINE...DB/Sirard
BEACHES...Sirard
SYNOPSIS...RK

weather.gov/losangeles

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