Area Forecast Discussion
Issued by NWS Los Angeles, CA

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419
FXUS66 KLOX 221841
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1141 AM PDT Thu Jun 22 2017

.SYNOPSIS...
The high will bring temperatures that are well above normal for the
inland areas and around normal at the coast into Monday. The skies
should be fair except where the onshore flow brings in a coastal
overnight marine layer through next week. A low will approach by
Tuesday for a cooling trend and increasing cloudiness into midweek.

&&

.SHORT TERM...(TDY-SAT)

Balloon soundings indicate a lowering of the marine lyr north Pt
Conception but an slight increase in the south with also a good
increase in the south to north gradients. This is making for
opposing temperature trends this morning with northern areas
warmer (in interior SLO there is double digit warming over
yesterday at this time), while in the south we`re seeing as much
as 15 degrees of cooling from yesterday, particularly in the lower
coastal valleys. Given these strong south to north gradient
trends it`s going to be much harder for the marine lyr to clear
from Malibu to SBA and highs south of Pt Conception will likely be
several degrees cooler than yesterday. Still quite hot though in
the mountains and Antelope Valley above the marine lyr where heat
warnings and advisories remain in effect. Up north the opposite is
expected, especially inland. Will make some adjustments to the
forecast this morning to account for these changes.

Not much change in this scenario Friday as gradients remain more
or less the same and the strength and location of the ridge aloft
are also unchanged. By late Friday night and Saturday there is a
shift in the gradients to northerly and this should lead to
earlier clearing and a warming trend, mainly south of Pt
Conception.

.LONG TERM...(SUN-WED)

Looks like one more day of real heat on Sunday. The ridge actually
slides a little to east but hgts remain at 593 DM. The GFS keeps
max temps the same while the EC has a little bit more of an
offshore push and actually warms things up a bit making it the
warmest day of the next 7. Gave a small nod to the EC and bumped
temps up a degree or two from Saturday. The heat products look
good through Sunday.

Both the EC and GFS agree that the ridge will break down Mon and
Tue. There should be some cooling each day away from the beaches
(which will see little or no change from the previous days. The
biggest drops will be felt in the vlys where the sea breezy will
finally be able to reach.

Disagreement for next Wednesday. The EC brings in a little ridge
while the GFS continues the trofing. Coordination and
collaboration between the surrounding offices resulted in a
preference for the cooler GFS pattern.

&&

.AVIATION...22/1800z.

At 1748z at KLAX...The marine layer depth was 1900 feet. The top
of the inversion was around 3500 feet with a temperature of about
27 degrees Celsius.

The marine layer will clear from most coastal sections, but some
TAF sites will not clear until late afternoon or not at all. Most
TAF sites will have VFR conditions except for MVFR conditions
where the marine clouds fail to clear out. The marine clouds will
return to the coastal and valley sections with IFR conditions again
tonight into Friday morning. There is good confidence in the 18z
TAF forecast.

KLAX...Good confidence in the 18z TAF. There is a 30 percent
chance of the marine clouds moving in plus or minus two or more
hours than the forecasted time.

KBUR...Good confidence in the 18z TAF. There is a 30 percent
chance of the marine clouds moving in plus or minus two or more
hours than the forecasted time.

&&

.MARINE...22/900 AM.

Winds will remain below Small Craft Advisory (SCA) level through
Friday then increase to above SCA levels in the outer waters Saturday
through Monday.

A 2-3 foot south swell will last through much of the week and
pose a risk for breaking waves nearshore. People boating or
kayaking near shore should use extra caution this week. A small
(2-3 feet) short period swell will impact the Santa Barbara
Channel and Santa Monica Basin over the weekend.

Although the coverage of dense fog is easing a bit, there is still
the possibility of patchy dense fog during the night and
mornings.

&&

.FIRE WEATHER...22/1030 AM.

Hot and dry conditions will continue through Monday of next week.
The hot conditions will also bring the potential for plume
dominated fires which can create their own intense winds. Onshore
winds will peak today and Friday, which will focus the concerns to
interior Los Angeles County including the Angeles National
Forest, Highway 14 corridor, and the foothills of the Antelope
Valley. Weaker but locally breezy northwest winds should follow
Saturday through Monday...shifting the area of concern to Santa
Barbara County and the Tejon Pass.

Tropical moisture aloft will move through the area Friday night and
Saturday. While this should have little impact on humidities at the
surface, this has a 10 percent chance of producing high-based
thunderstorms. Confidence is incredibly low with this, but the
potential for dry lightning exists.

A Red Flag Warning is in effect through 9PM this evening for
the interior Los Angeles County Mountains and Foothills where the
driest and windiest conditions of the period are expected.
Otherwise, with rapidly drying fuels/vegetation, elevated fire
weather concerns through Monday, primarily over all interior
sections away from the influence of the marine layer. If fire
ignition occurs, dangerous fire behavior should be expected. As
such, the public should be extreme careful when handling potential
ignition sources such as cigarettes, campfires, hand torches and
metallic weed trimmers.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory in effect until 9 PM PDT Sunday for zones
      38-52-53. (See LAXNPWLOX).
     Beach Hazards Statement in effect through Friday evening for
      zones 40-41-87. (See LAXCFWLOX).
     Excessive Heat Warning in effect until 9 PM PDT Sunday for
      zones 54-59. (See LAXNPWLOX).
     Red Flag Warning in effect until 9 PM PDT this evening for
      zone 254. (See LAXRFWLOX).
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK...(SAT-WED)
Hot temperatures with potential heat impacts will continue for
the Antelope Valley and San Gabriel Mountains through Sunday and
possibly other areas as well.

&&

$$

PUBLIC...MW/Rorke
AVIATION...Sweet
MARINE...Sweet
FIRE...Kittell
SYNOPSIS...STu

weather.gov/losangeles



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