869
FXUS66 KLOX 082244
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
344 PM PDT Mon Jul 8 2024

.SYNOPSIS...08/132 PM.

A long-lasting and extreme heatwave will continue across the
mountains and interior areas through much of the week as a strong
high pressure system remains anchored over the region. A high
risk for dangerous heat illness exists across the interior
portions of the area. A cooling trend is expected by Friday and
the weekend but temperatures will remain well above normal inland.

&&

.SHORT TERM (TDY-THU)...08/202 PM.

Going into the second week now of this unprecedented heat wave for
interior areas. Today is now the fifth consecutive day with
temperatures at or above 110 degrees in the Antelope Valley and
odds are high that there will be at least 4 more after today. The
previous record had been three days at or above 110. Paso Robles
had three straight days of 110+ before the big onshore push
yesterday ended that streak. However, temperatures are headed back
up today with highs close to 110 Tue-Thu.

The high pressure ridge over California will remain in place
through Thursday but start weakening going into the weekend as a
trough develops over the Pac NW. In the meantime, weakening
onshore flow will bring hotter temperatures back to the valleys
and parts of the coastal areas. Not expecting to see a return of
the 118 in the Santa Clarita Valley, but highs around 110 are
possible in the warmer valleys Tue-Thu. Excessive heat warnings
are in place across the valleys and interior areas through at
least Thursday, and for the Antelope Valley and interior SLO
County through Saturday. Coastal areas will be cooler but still
4-8 degrees above normal with areas of dense fog possible at the
beaches.

Increasing northerly flow aloft across the western parts of the
SLO/SB Counties Tue and Wed evenings will bring some gusty winds
to those areas but especially across southwest SB County and the
interior SB Mountains. Based on the latest ensemble guidance and
gradients it will be a close call whether they reach advisory
levels, but certainly some gusts between 30-40 mph.

.LONG TERM (FRI-MON)...08/214 PM.

A slow cooling trend is expected to begin Friday as the high
weakens and weak troughing develops along the West Coast. However,
highs across the Antelope Valley will still remain at or above
105 through the weekend which is 4-8 degrees above normal.
Similar cooling trend elsewhere as well with highs remaining at
least a few degrees above normal through Sunday with additional
cooling next Monday.

Ensemble models showing some increasing moisture aloft moving in
from the southeast this coming weekend. Thunderstorm chances are
too low (5-10%) to include in the forecast at this time and would
mostly likely just impact the far eastern San Gabriels at most.
Probably just some increasing cumulus over the peaks but something
to monitor over the coming days.

&&

.AVIATION...08/2057Z.

At 20Z at KLAX, the marine layer was 1100 feet deep. The top of
the inversion was at 4200 feet with a temperature of 31 deg C.

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

Moderate to high confidence in KBUR TAF.

Moderate confidence in remaining TAFs at coastal sites and
coastal valley sites. For these locations, vsby/cig restrictions
will continue to clear this afternoon, and then IFR to LIFR
vsbys/cigs will return tonight through Tuesday morning. Smoke will
further contribute to vsby restrictions, especially at KSBA.
Timing of flight category changes may vary +/- 2-3 hours from
forecasts. There is a 30% chance for minimum vsbys/cigs to be off
by a category.

KLAX...Moderate confidence in TAF. There is a 30% chance for
vsbys/cigs to become VLIFR tonight and Tuesday morning. No
significant east wind component is expected.

KBUR...Moderate to high confidence in TAF. There is a 40% chance
for MVFR vsbys/cigs to occur tonight into Tuesday morning.

&&

.MARINE...08/157 PM.

In the Outer Waters, Small Craft Advisory (SCA) winds are
expected this afternoon through Wednesday night. Thereafter, SCA
winds are not expected late this week into the upcoming weekend.

In the Inner Waters N of Pt. Sal, there is a 30% chance of SCA
winds during the afternoon and evening of today and Tue.
Otherwise, SCA conditions are not expected this week into the
upcoming weekend.

In the Inner Waters S of Pt. Conception, SCA winds are forecast from
Tuesday afternoon through Tuesday night across the westernmost
portion of the Santa Barbara Channel -- mainly from Santa Cruz
Island to the Santa Barbara County South Coast from Pt. Conception
to Refugio State Beach. Otherwise, SCA conditions are not
expected this week into the weekend.

Dense fog is expected across the coastal waters through at least
Tuesday morning. Please reference the Marine Weather Statement for
additional information.

&&

.FIRE WEATHER...08/343 PM.

Long lasting and extremely hot conditions will continue through much
of this week across the interior. For today through Thursday, very
hot temperatures and low humidities will continue across the interior
valleys, mountains, and deserts with highs between 100 and 115 degrees
and minimum humidities between 5 and 15 percent (hottest and driest
in the Antelope Valley). Onshore flow will remain fairly strong today,
but weaken over the next few days, allowing the hotter temperatures
and lower humidities to spread into the coastal valleys and Santa
Monica/Santa Ynez mountains, bringing elevated fire weather concerns
to those areas as well. Onshore wind gusts between 25 and 35 mph
will be common this afternoon and evening across the interior,
then 20 to 30 mph the next few days. However, there will be increasing
northwest winds across portions of Santa Barbara county and the I-5
corridor Tuesday afternoon through Tuesday night. Specifically,
there is expected to be northwest wind gusts of 25 to 35 mph across
the Santa Barbara county interior mountains Tuesday afternoon/evening
(including the higher elevations of the Lake Fire), and 35 to 45
mph across the western Santa Ynez mountains and adjacent foothills
from late Tuesday afternoon through Tuesday night. These gusty
winds combined with hot temperatures and low humidities between 5
and 15 percent will likely bring critical Red Flag conditions,
resulting in the Fire Weather Watch being upgraded to a Red Flag
Warning. In addition, there will be increasing northwest winds
with gusts of 25 to 35 mph across the I-5 corridor Tuesday afternoon
into Tuesday night, resulting in heightened fire weather concerns
for this region. In addition, the hot and unstable conditions
will make conditions favorable for large vertical plume growth
with any new or existing fires (Lake Fire), as projected mixing
heights between 10,000 and 20,000 feet will be common. Areas under
a large plume dominated fire can expect to have gusty and erratic
surface winds and the potential for extreme fire behavior.
Conditions remain favorable for large fire growth and extreme fire
behavior across the valleys, mountains, and Antelope Valley,
especially in the Red Flag Warning area.

Very hot conditions will change little over the interior through much
of the week, with only a few degrees of cooling possible by the
weekend. This will result in a continuation of elevated to brief
critical fire weather conditions across the interior through the
week. The upper level flow pattern becomes more favorable to bring
some mid level monsoonal moisture into the mountains and deserts
by the weekend, with a 5 to 10 percent chance of thunderstorms for
these areas. This is one of the longest and most extreme heat
waves on record for interior areas. For the foreseeable future,
there will be a higher risk for large fires and plume dominated
fires across the interior. There is a high risk for heat related
illness as well.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning now in effect until 9 PM PDT Saturday
      for zones 38-343>345-353-376>379-381>383. (See LAXNPWLOX).
     Heat Advisory remains in effect until 10 AM PDT Tuesday for
      zones 88-357-358-371-372-375. (See LAXNPWLOX).
     Excessive Heat Warning in effect from 10 AM Tuesday to 9 PM
      PDT Thursday for zones 88-356>358-369>375-548. (See LAXNPWLOX).
     Excessive Heat Warning remains in effect until 9 PM PDT
      Thursday for zones 351-352-380. (See LAXNPWLOX).
     Red Flag Warning in effect from 3 PM Tuesday to 3 AM PDT
      Wednesday for zone 351. (See LAXRFWLOX).
     Red Flag Warning in effect from noon to 9 PM PDT Tuesday for
      zone 353. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect from 3 PM Tuesday to 3 AM PDT
      Wednesday for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Thursday for
      zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW
AVIATION...Cohen
MARINE...Cohen
FIRE...Gomberg
SYNOPSIS...MW

weather.gov/losangeles

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