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Area Forecast Discussion (AFD)

Issued by Los Angeles, CA (LOX)

                            
000
FXUS66 KLOX 202232
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA 
332 PM PDT Tue Aug 20 2019

.SYNOPSIS...20/1234 PM.

Conditions will warm into Wednesday, then cool back to near 
normal values by the end of the week. Morning low clouds and fog
will continue to affect coastal areas, becoming more widespread
by the end of the week.

&&

.SHORT TERM (TDY-FRI)...20/153 PM.

Marine layer clouds have pretty much dissipated across the area,
even including most of the coastal waters as heights build aloft, 
onshore flow decreases, and more importantly northerly flow 
increases. North/south gradients are 1-2mb stronger than they were
yesterday at this time and models are indicating a stronger and
more widespread wind event for southern SB County. Still primarily
a western portion event but likely pushing closer to the beaches
rather than being confined to just the elevated areas. Later on
any marine layer return should be confined to the Central Coast 
and LA County but pretty low confidence even with that.

After the 5 or so degrees of warming today most valleys tomorrow
should again see another 5 degrees of warming, pushing highs to at
or slightly above 100 for the warmest valley locations. Coastal
areas will be warmer as well, especially southern SB County where
the downsloping Sundowner winds will provide an additional 
heating factor. Wind speeds in that area are expected to be a
notch higher than today so another wind advisory will likely be
needed. 

Wednesday should be the warmest day as a trough moving through to
the north will introduce a cooler air mass and onshore trends on
Thursday and Friday. By Friday daytime highs should be very close
to normal and the marine layer will likely return to all coastal
areas as well and possibly some valleys.

.LONG TERM (SAT-TUE)...20/204 PM.

Fairly uneventful period of weather over the weekend into early
next week. The ridge rebuilds Saturday and Sunday which should
lead to a few degrees of warming in most areas, but moderate
onshore flow is expected to remain in place so we'll likely see a
shallow but widespread marine layer near the coast during the
night and morning hours at least. 

No monsoon moisture expected through the weekend. The GFS shows a
tropical cyclone spinning up off the southern Baja coast early
next week and it's possible we could see some mid and high clouds
from it but too dry at lower levels to pose much of a risk for
convection.

&&

.AVIATION...20/1832Z.

At 1709Z at KLAX, the marine layer depth was 1100 ft. The top of 
the inversion was around 2400 ft with a temp of 23C.

The marine layer depth ranges from 900 feet south of Point
Conception to 1500 feet on the central coast. North flow across
the area will limit the inland push of marine clouds tonight and
Wednesday morning. Therefore, TAF sites on the central coast and 
Los Angeles county coast have the best chance of marine cloud
intrusion with either MVFR or IFR ceilings.

KLAX...Low to moderate confidence in the 18z TAF. There is a 40% 
chance for VFR conditions through the period. Low clouds will be 
patchy in nature. Good confidence in no east wind component over 
3 KT.

KBUR...High confidence in CAVU 18z TAF.

&&

.MARINE...20/157 PM.

Outer Waters...moderate to high confidence in current forecast. 
Small Craft Advisory (SCA) level winds are expected to continue 
through at least early Wednesday afternoon. There is a 30% chance
that winds will briefly drop below SCA levels late tonight and 
Wed morning. Gale warnings have been issued across the outer 
waters including areas NW of San Nicolas Island from Wednesday 
afternoon through early Thursday morning. 

Inner waters north of Pt Sal...Fair confidence in forecast with a
60% chance of SCA level winds during the afternoon and evening 
today and Wednesday and a 40-50% chance on Thursday.

For the Inner Waters south of Point Conception...Good confidence
in forecast. There is a 60% chance for SCA level NW to N winds
across the western portions of the SBA Channel late this afternoon
through late tonight and once again during the same times
Wednesday. Not expecting Sundowner winds on Thursday.

&&

.FIRE WEATHER...20/329 PM.

Very warm and dry conditions will continue across interior sections
through Thursday. Peak temperatures are expected Wednesday when 
warmest mountain, desert, and valley areas will top 100 degrees. 
Minimum humidities between 10 and 20 percent will be common across 
interior areas through Thursday, with some single digit readings in 
the mountains and Antelope Valley, especially Wednesday. In addition 
to the typical gusty onshore winds in the afternoon and evening 
hours, there will be some northerly breezes during the overnight and 
early morning hours across the Interstate 5 and Highway 33 corridors 
in the mountains and Santa Clarita Valley. 

Gusty sundowner winds with warm and dry conditions will also bring
elevated fire danger to the Santa Barbara south coast and foothills
through Wednesday night, especially western portions where winds 
will be strongest. Wind gusts between 35 and 45 mph will be common 
in the canyons and foothills from Gaviota to Goleta during the late
afternoon through nighttime hours (with isolated gusts to 50 mph near
Gaviota), along with gusts in the 25 to 35 mph range during the 
overnight hours in the hills above Montecito and Carpinteria. Minimum
humidities through this evening are expected to remain in the 25 to 
40 percent range, then lower to between 15 and 30 percent on 
Wednesday afternoon and evening, when temperatures will likely climb
above 90 degrees in warmest foothill and canyon locations. Peak
Santa Barbara-Santa Maria gradients are expected to be around -4.0
mb this evening and Wednesday evening, with peak Santa Barbara-
Bakersfield gradient expected to be -3.0 to -3.5 mb late tonight.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 3 AM PDT Wednesday for zones
      39-52. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday for
      zones 645-650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT Wednesday for
      zones 670-673-676. (See LAXMWWLOX).
     Gale Warning in effect from 3 PM Wednesday to 3 AM PDT
      Thursday for zones 670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (FRI-TUE).

No significant hazards expected.

&&

$$

PUBLIC...MW
AVIATION...Sweet/Kaplan
MARINE...Sweet
FIRE...Gomberg
SYNOPSIS...Kittell

weather.gov/losangeles