Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 221215
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
515 AM PDT Sat Jul 22 2017

...Aviation discussion updated...

.SYNOPSIS...

For the next few days a typical summer weather pattern will bring
night through morning low clouds and fog to the coasts and some of
the valleys. Temperatures will be near normal. There is a slight
chance of thunderstorms in the afternoons and evenings for the
deserts and mountains on Monday and Tuesday.

&&

.SHORT TERM...(TDY-MON)

The marine layer is 1400 feet deep and there is a 3 MB push to the
east and a 1 MB push to the north. Marine layer stratus is
currently at KLAX and is slowly advancing up the coast to the NW.
Stratus covers most of western SBA county and is slowly moving
into SLO county. By dawn the low clouds will be into the VTA
coastal plain and the SGV. There is about a 50/50 chance that the
low clouds will make it into the SBA south coast this morning. The
low clouds will burn off by mid morning or shortly there after
and the entire area will see sunny skies in the afternoon. MAx
temps will be right around normal.

A very weak trof will move towards the coast later tonight and the
onshore gradients will strengthen by a MB or two. This will deepen
the marine layer and will bring the low clouds in earlier. The
deeper marine layer and stronger push will also allow a little
better stratus coverage in the vlys. Burn off (dissipation to be
rigorously accurate with the wording) will occur an hour or two
later than today but the afternoon will still be sunny. The deeper
marine layer...stronger onshore flow...and lower hgts will allow
for a couple of degrees of cooling across the area.

Monday`s forecast really depends on what mdl is right. The GFS has
quite the bullish monsoon forecast. It pushes PWAT values as high
as 1.4 inches VTA and SBA Counties. LI`s lower to -1 or -2. The
only question with the GFS forecast is how much mid and high level
clouds will arrive with the moisture...there is a chance that the
day could be mostly cloudy which would inhibit the convection.
Still if the GFS is perfect...there will be a great deal of
convection in the afternoon and evening across the mtns and the AV
as will as the Santa Clarita and San Gabriel Vlys.

But...The EC keeps all the moisture to the S and E of the area.
The GFS has been over forecasting the monsoon front fairly
relentlessly over the past three weeks and tend to favor the drier
EC at this time. Still cannot ignore the GFS (hey its gotta be
right sometime) and have slight chc pops in the fcst for now. Will
have to monitor this and see which mdl trends to the other.

More low clouds and fog can be expected for the coast and some
adjacent vlys Sun night into Mon morning, otherwise partly cloudy
skies can be expected across the region for the most part during
the period.

Hgts continue to lower and there will be more clouds so Monday`s
temps will continue to cool and will be 2 to 5 degrees blo
normal.

.LONG TERM...(TUE-FRI)

Southwest flow returns on Tuesday. The GFS has just enough
residual moisture to warrant a slight chc of TSTMs in the
afternoon but mostly likely it will be dry. Hgts will be the
lowest of the week and Tuesday should be the coolest day of the
week. There will probably be enough mid level clouds as well as
possible low level mixing to eliminate the low clouds for the
morning.

The upper high to the east of the area then grows and reasserts
itself into the area. The inversion will strengthen and the night
through morning low cloud patter will resume but only for the
coasts. Max temps will trend higher each day and it looks like
next weekend could be a warm one.

&&

.AVIATION...22/12z

At 0930z at KLAX... the inversion was around 1400 feet. The top
of the inversion was around 3500 feet with a temperature of about
29 degrees Celsius.

Overall... Moderate confidence in the current coastal TAFs and
high confidence elsewhere. LIFR/IFR conditions will continue to
develop over coastal locations through daybreak but there is a
forty percent chance that CIGs or low VSBY will not develop at
KSBA... KOXR... or KCMA or will be fleeting. Conditions will clear
to VFR between 15z-17z with a twenty percent chance of the
reduced conditions lingering until 19z at KLAX and/or KLGB.
Similar conditions and timing will return to coastal locations
after 08z. Otherwise and elsewhere VFR conditions will prevail.

KLAX... Moderate confidence in the current TAF. LIFR/IFR conditions
will impact the terminal through 17z with a twenty percent chance
of conditions lingering through 19z. Similar conditions will
return after 09z. Otherwise VFR conditions will prevail. East
winds greater than 7 knots are not expected.

KBUR... Moderate to high confidence in the current TAF. VFR
conditions will prevail through the forecast period.

&&

.MARINE...22/230 AM...

Small Craft Advisory (SCA) level winds across the Outer Waters will
continue through this evening. Otherwise and elsewhere winds and
seas will remain below SCA levels through Wednesday.

&&

.BEACHES...22/230 AM.

Significant surf may impact Southern California beaches beginning
late next week. This is due to a developing tropical cyclone off
the Mexican coast that could produce 25 to 35 foot swells off Baja
California. A moderately long period swell may impact the Southern
California coastline as early as next Friday and build into next weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through Sunday evening for
      zones 40-41-87. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
      for zones 670-676. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Sunday for zone
      673. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(MON-FRI)
A monsoonal flow pattern Monday will bring a slight chance of
thunderstorm to the mountains and deserts on Monday and Tuesday.
There is a possibility that shower activity could spill over into
the valley areas.

&&
$$

PUBLIC...Rorke
AVIATION...Kj
MARINE...Kj
BEACHES...Kj
SYNOPSIS...STu

weather.gov/losangeles



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