Area Forecast Discussion
Issued by NWS Los Angeles, CA

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754
FXUS66 KLOX 221108
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
408 AM PDT Fri Jun 22 2018

.SYNOPSIS...22/319 AM.

Upper level high pressure will result in hot weather across
inland areas today. A trough dropping through the Pacific
northwest and into the Great Basin will bring a cooling trend
over the weekend. Some warming is expected early next week, with
temperatures a few degrees above normal in most areas Monday
through Wednesday. Cooler weather is expected Thursday as a trough
moves into the West Coast.

&&

.SHORT TERM (TDY-SUN)...22/353 AM.

The marine layer was just under 2000 feet deep early this morning,
about the same as it was Thu morning at this time. Low clouds
were widespread in all coastal and valley areas with the
exception of the interior valleys of SLO County, the Cuyama Valley
and the Santa Clarita Valley. However, expect some clouds to push
into the Santa Clarita Valley for a couple of hours this morning,
and clouds could even push into the Salinas Valley as well. Expect
skies to clear by mid morning in the valleys and late morning
across most of the coastal plain. However, some clouds could
linger at some beaches into the afternoon.

Despite the rather deep marine layer, models continue to show
warming at 950 mb along with a decrease in onshore pressure
gradients this afternoon compared to Thu afternoon. Therefore,
expect a few degrees of warming in the valleys and across interior
sections of the coastal plain. There may be couple of degrees of
warming in the mtns, interior valleys of SLO and SBA Counties and
the Antelope Valley, with mostly minor changes in max temps near
the coast. Although it will be hot inland, expect temps to remain
below Excessive Heat Warning levels in the Antelope Valley. Temps
could get close to advisory levels in the interior valleys of SLO
County, but believe they will be just below those levels.

An upper low will drop southward through Idaho tonight and
Saturday, and heights across the region will drop a bit. Onshore
gradients should increase as well. An eddy circulation will
develop across the inner waters, which would deepen the marine
layer a bit. Overall though, expect a similar low cloud pattern
tonight/Sat morning, with widespread clouds in all coastal and
valley areas with the exception of the far interior valleys of SLO
County and the Cuyama Valley. Max temps should be down a few
degrees in most areas, except there will be minor changes near the
coast. Cooling should be most pronounce in the warmer valley
locations of L.A. and VTU Counties on Sat. Gusty winds in the
Antelope Valley could approach advisory levels Sat afternoon.

The upper low will move into the Rockies Sat night and Sun, with a
very weak broad trough extending into the forecast area. Models
are showing a rather strong southerly surge will be located just
east of the region Sat night and Sunday, which should help deepen
the marine layer and bring cool marine all the way to the coastal
slopes. Models show significant cooling at 950 mb on Sun. Expect
plenty of night through morning low clouds, possibly to the
coastal slopes, with slower clearing on Sunday. Clouds may well
linger through the afternoon in coastal areas south of Pt
Conception on Sunday. There should be significant cooling in all
areas west of the mtns on Sunday, with the exception of portions
of the Santa Ynez Valley and the Central Coast, where downslope
southerly winds will provide warming in places like Lompoc and
Vandenberg. There will be less cooling in the higher mtns and
Antelope Valley.

.LONG TERM (MON-THU)...22/407 AM.

Heights will rise a bit across the region on Monday, and onshore
gradients will relax a bit, especially in the N-S direction.
Expect faster clearing on Mon, and with some warming at 950 mb,
there should be a few degrees of warming in the valleys and across
interior sections of the coastal plain, generally to a bit above
normal levels. It will remain hot in the mtns and deserts, with
temps several degrees above normal. Do not expect too much change
in the weather Tue and Wed, with night through morning low clouds
in coastal and most valley areas, and mostly minor changes in max
temps. A trough moving into the West Coast should bring cooling to
most areas on Thu.

&&

.AVIATION...22/1018Z.

At 1000Z, the marine inversion at KLAX was based at 1900 feet. The
top of the inversion was 4600 feet with a temperature of 28
degrees Celsius.

Overall for 12Z TAF package, low confidence in coastal TAFs,
moderate confidence in valley TAFs and high confidence in desert
TAFs. IFR conditions will dissipate across the valleys by late
this morning. For coastal sites (especially south of Point
Conception), confidence in CIG/VSBY forecast is low as clouds may
or may not dissipate this afternoon.

KLAX...low confidence in 12Z TAF. There is a 50% chance that MVFR
CIGs will not dissipate this afternoon. For tonight, low
confidence in timing of flight category changes.

KBUR...moderate confidence in 12Z TAF. There is a 30% chance that
IFR/MVFR conditions could persist to 18Z. For tonight, high
confidence in return of flight restrictions, but low confidence in
flight category (equal chance of IFR or MVFR conditions) and
timing (could be +/- 3 hours of current 07Z forecast).

&&

.MARINE...22/318 AM.

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) level winds will continue through Saturday
morning with a 60% chance of SCA level winds continuing into
Saturday evening. Winds will remain below SCA levels Sunday and
Monday. On Tuesday, there is a 70% chance of SCA level winds.

For the Inner Waters, high confidence in current forecast. For the
waters north of Point Sal, winds and seas will remain below SCA
levels through Tuesday.

For the waters south of Point Conception, winds and seas will
remain below SCA levels through Tuesday. However, both
tonight/Saturday morning and again Saturday night/Sunday morning,
southeast winds are anticipated with a 50% chance of Southeast
wind gusts between 10 and 15 kt.

&&

.FIRE WEATHER...21/824 PM.

Elevated to brief critical fire weather conditions are expected
to continue across interior areas through Saturday due to the
combination of hot temperatures, low humidities, and breezy
conditions. Already saw some triple digit readings with single
digit humidities across the region earlier this afternoon. Hotter
temperatures are expected on Friday as a weak offshore wind
influence develops across interior sections in the morning,
resulting in more widespread triple digit readings across the
lower mountains, deserts, and interior valleys of SLO County. In
fact, many portions of the Antelope Valley could see highs ranging
between 105 and 108 degrees on Friday, possibly reaching up to
110 degrees far eastern portions. In addition, there will be
widespread humidities falling into single digits across these same
locations. Due to the expected hot and unstable conditions along
with drying fuels, any fires that develop across interior sections
will have the potential for large plume growth. By late afternoon
and evening, expecting some gusty onshore winds to develop across
interior sections. By Saturday, temperatures and humidities will
moderate slightly, but there will be increasing onshore winds
during the afternoon and evening that will continue the elevated
to brief critical fire weather conditions.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 9 AM PDT Saturday for
      zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Saturday for
      zone 676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (SUN-THU).

No significant hazards expected.

&&

$$

PUBLIC...DB
AVIATION...RAT
MARINE...RAT
FIRE...Gomberg
SYNOPSIS...DB

weather.gov/losangeles



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