Duarte Weather

000
FXUS66 KLOX 190626
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1126 PM PDT Fri Sep 18 2020

.SYNOPSIS...18/627 PM.

Temperatures will cool through Monday then warm again into next
weekend. There will be gusty northerly winds across southern
Santa Barbara County through Saturday morning. Overnight and
morning low clouds and fog will expand into most coastal and
lower valley areas by Monday.

&&

.SHORT TERM (FRI-MON)...18/823 PM.

***UPDATE***

The marine inversion early this evening ranged from near 500 ft
deep at LAX to near 800 ft deep at VBG. Low clouds were expanding
along the Central Coast this evening and should push into the
Santa Ynez Vly later tonight. Low clouds should also develop over
the SoCal Bight later tonight and move into the immediate coast
of L.A.County by daybreak or so. With the shallow marine
inversion, there should also be patchy dense fog with any low
clouds overnight. Otherwise, mostly clear skies can be expected
across the region thru the night.

Good northerly pressure gradients this evening across SBA County
(NAM fcst SBA-SMX -3.6 mb at 06Z) will continue strong and gusty
NW to N canyon winds across the SBA County S coast and Santa Ynez
Mtns mainly from San Marcos Pass westward. Gusts up to 50 mph
have been observed at the SCE San Augustin automated wx station
west of Gaviota, with gusts up to 48 mph at the Refugio RAWS.
These wind gusts will likely persist overnight into early Sat. A
Wind Advisory is in effect for this area overnight thru mid-
morning Sat. Please see the latest Non-Precipitation Weather
Message (LAXNPWLOX) for further details.

***From Previous Discussion***

A cooling trend will continue through the weekend and into Monday
along with a deepening marine layer. The latest AMDAR soundings
from KLAX indicate a marine layer depth closer to 600 feet deep.
The marine layer depth should deepen to near 1000 feet deep by
Saturday morning, possibly thinning slightly for Sunday morning,
then deepening again on Monday. Middle and high level cloudiness
from what used to be tropical storm Karina will continue to thin
out across the region tonight which should allow for better
stratus formation.

With the trough moving over the region, the smoke that has been
in place the last couple of weeks will clear out over a majority
of the area. Increasing southwest flow in the boundary layer will
increase transport winds and the trough should enhance mixing.
The smoky skies should continue to improve across the area,
except for portions of Los Angeles County where the Bobcat Fire is
still actively burning at this time.

A dying boundary north of the region will move south and tighten
the northerly pressure gradient through Sunday. Marginally gusty
Sundowner winds are already occurring this afternoon and will
increase across southern Santa Barbara County later and linger
into Saturday morning. A wind advisory remains in effect from 4 pm
PDT this afternoon through 9 am PDT Saturday morning. Gusts up to
45 mph are possible, especially west of Goleta out toward the
Gaviota area. If traveling across this area, gusty cross winds are
possible on Highways 101 and 154 this afternoon and tonight. If
planning any outdoor recreational activities this afternoon and
evening, such as kayaking out near Gaviota and Refugio, it might
be best to delay these activities when these winds may not present
hazardous weather and/or sea conditions.

A tricky cloud forecast is on tap for tonight. Cold air advection
could make for little marine layer induced stratus south of Point
Conception. The previous forecast was scaled back for a later
arrival. Little, if any stratus should make into the Ventura
County Coast or the Santa Barbara South Coast. Better confidence
exists for the Central Coast and the Santa Ynez Valley. Night
through morning low clouds and fog should start to expand into
Saturday night and Sunday as the eddy circulation should allow for
better coverage.

Zonal flow should setup for Sunday between troughs as the trough
along the southern Oregon coast lifts out and another trough dips
in behind it. The marine influence should continue to win out for
the coast and lower valley, keeping a cooling trend going. Less
confidence for the mountains and desert as these areas could end
warming.

.LONG TERM (TUE-FRI)...18/138 PM.

The influence of the trough should linger into Tuesday and keep
cooler temperatures in place. The deepest marine layer of the week
should be in place between Monday and Tuesday, then ridging aloft
should start to build into the region and thin the marine layer.
A warming trend will develop for the latter half of the week. By
Thursday or Friday, stratus coverage could be minimal as weak
offshore flow develops. For the current time, no gusty offshore
winds are expected, but this will need to be monitored closely for
development.

&&

.AVIATION...19/0624Z.

At 0515Z at KLAX, there was no marine layer. There was a sfc based
inversion with a top at 2300 feet and a temperature of 30 C.
Moderate confidence in coastal TAFs and good confidence in inland
TAFs xcp for KPRB where there is a 40 percent chc of no cigs..

Cstl TAFs KSBA and south have a 20 percent chc of MVFR VIS 10Z-16Z
and a 10 percent chc of LIFR Cig/Vis 11Z-15Z.

KSMX and KSBA flight cat change timing could be off by +/- 90
minutes. KSMX and KSBA have a 30 percent chc of 1/4SM VV001 11Z-
15Z.

KLAX...High confidence in TAF through 11Z, then moderate
confidence. There is a 30% chance of 2SM OVC004 11Z- 6Z. High
confidence that there will be no east wind component greater than
4 kt.

KBUR...High confidence in TAF.

&&

.MARINE...18/826 PM.

Across the outer waters... Small Craft Advisory (SCA) level wind
will continue through Saturday night and there is a forty percent
chance of it continuing through Sunday night. SCA level winds will
develop again Tuesday and Wednesday. The strongest winds will be
in the afternoon and evening hours. Otherwise, conditions will
remain below SCA level through the forecast period.

Across the nearshore waters of the Central Coast... There is a
forty percent chance of SCA level wind during the afternoon and
evening hours through Saturday night. Otherwise, conditions will
remain below SCA level through the forecast period.

Across the inner waters south of Point Conception... SCA level
wind will continue across the western portion of the Santa
Barbara Channel through Saturday night. Otherwise and elsewhere,
conditions will remain below SCA level through the forecast
period.

Patchy fog will continue into next week across the coastal waters.
The poorest visibility and most widely spread conditions will
occur in the overnight and morning hours.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 9 AM PDT Saturday for zones
      39-52. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Sunday for
      zones 650-670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (MON-FRI).

No significant hazards expected.

&&

$$

PUBLIC...Hall/Sirard
AVIATION...Rorke
MARINE...Kj
SYNOPSIS...Kj

weather.gov/losangeles

NWS LOX Office Area Forecast Discussion