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Area Forecast Discussion (AFD)

Issued by Los Angeles, CA (LOX)

                            
000
FXUS66 KLOX 230702
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA 
1202 AM PDT Tue Oct 23 2018

.SYNOPSIS...22/1027 PM.

Temperatures will trend cooler through midweek then warm 
significantly late in the week. Overnight and morning low clouds 
and fog will return to coastal and adjacent valley locations 
throughout the week.

&&

.SHORT TERM (TUE-FRI)...22/818 PM.

A weak upper level trough combined with onshore flow bringing
a mix of higher level clouds and low clouds to the region
this evening. The higher clouds are focused south of Point
Conception, and the low clouds are currently moving into coastal
areas of LA/Ventura counties as well as the Central Coast. ACARS
data showed marine layer depth around 1500 feet across the LA
Basin, with low clouds likely reaching into some of the lower
valleys overnight. Localized gusty northwest winds occurring
across the western portions of the Santa Barbara south coast and
Santa Ynez mountains, with Gaviota and Refufio RAWS stations
reporting gusts in the 35 to 40 mph range. Current Santa Barbara-
Santa Maria gradient at -2.9 mb.

With weak upper level trough moving east of the area on Tuesday,
dry northwest flow aloft develops. This will result in 3 to 5
degrees of warming across many areas on Tuesday. On Tuesday night,
look for sundowner winds to a bit stronger and more widespread
as Santa Barbara-Santa Maria gradient peaks around -3 mb in the
evening and Santa Barbara-Bakersfield gradient peaks around -4.5
during the overnight hours. As a result, looking for potential
wind advisory conditions, with gusts in the 30 to 40 mph range,
and isolated gusts up to 45 mph in favored locations such as the
hills above Gaviota and Refugio. As marine layer shrinks, looking 
for low clouds and fog to be less widespread on Tuesday night.

*** From previous discussion ***

Synoptically, the upper level trough axis will transition
eastward across Southern California through Tuesday night before 
exiting east. Replacing it as the feature driving our weather will
be an broad upper level ridge approaching from west to east 
across the Eastern Pac. Wednesday will largely be a transitional 
day and then the ridge will move far enough eastward by Thursday 
to make itself felt. The ridge will then expand and strengthen 
further inland Friday allowing more significant warming and 
increased offshore flow.

Some additional warming is expected on Wednesday as onshore flow 
weakens while the upper ridge starts to strengthen and nudge in 
over the region. High temps should increase 2 to 5 degrees for the
most part. Best warming across the valleys and inland areas. 
Wednesday night to Thursday morning will be the last of the marine
layer low clouds and fog.

Thursday will see the ridge a bit more firmly established and
temperatures will rise a couple more degrees accordingly. Skies
should be mostly clear.

.LONG TERM (SAT-TUE)...22/213 PM.

Numerical guidance remains in good agreement with the large scale
features, keeping upper-level higher pressure over our area 
through the weekend. 
At lower levels, northerly winds will shift to the northeast by 
Friday bringing another round of Santa Ana winds to the wind 
prone areas of Los Angeles and Ventura Counties. This looks to be
a fairly weak event at this time, but the afternoon high
temperatures will rise significantly Friday - in some inland 
coast or coastal valleys locations they will reach the lower 90s.
So probably not record World Series weather like last year, but
definitely well above-average conditions.  
Winds and temperatures will fall off on Saturday but it will
remain warm.
The ridge should weakens on Sunday and Monday and the winds will
trend onshore leading to 3 to 6 degrees of cooling across the 
coasts and valleys.

&&

.AVIATION...23/0701Z.

At 0600Z, the marine inversion at KLAX was based around 1200 
feet. The top of the inversion was 2300 feet with a temperature 
of 19 degrees Celsius. 

Overall, moderate confidence in TAFs. Arrival timing may be off
by as much as two hours. flight cats may bounce between IFR and
Low MVFR. VFR transition should occur within 1 hour of fcst.

KLAX...Moderate confidence in TAF. Sky conds will bounce between
SCT and BKN through 10Z. Flight Cat will bounce between 008 and
012. Good confidence that VFR transition will occur between 17Z
and 19Z. Good confidence that any east wind component will be
under 5 kt.

KBUR...Moderate confidence in 00Z TAF. There is a 30 percent chc
of no cigs. If cigs do arrive there is a 30 percent chc of cigs no
lower than BKN006. Good confidence that VFR transition will occur
between 16Z and 17Z.

&&

.MARINE...22/819 PM.

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) level northwest winds will continue through
tonight. For Tuesday and Wednesday, there is a 70% chance of SCA
level winds, especially in the afternoon and evening hours, with 
a 50% chance of SCA level winds on Thursday. Hazardous short
period seas will continue. 

For the Inner Waters north of Point Sal, moderate confidence in 
current forecast. SCA level winds have subsided this evening, and
for Tuesday through Thursday there is a 50% chance of SCA level 
winds each afternoon and evening.

For the Inner Waters south of Point Conception, high confidence in
current forecast. There is a 30% chance of SCA level winds across
the western half of the Santa Barbara Channel during the late 
afternoon and evening hours on Tuesday.

&&

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

&&

.HAZARD POTENTIAL OUTLOOK (FRI-TUE).

No significant hazards expected.

&&

$$

PUBLIC...Gomberg/jld
AVIATION...Rorke
MARINE...RAT/Smith
SYNOPSIS...Kj

weather.gov/losangeles