Duarte Weather

000
FXUS66 KLOX 200256
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
756 PM PDT Thu May 19 2022

.SYNOPSIS...19/159 PM.

Cooler temperatures will be prevalent along with night through
morning low clouds and fog through the weekend as onshore flow
strengthens. Low clouds will be stubborn to clear across the
Southland Friday and Saturday. A warming trend is expected early
next week as high pressure develops.

&&

.SHORT TERM (THU-SUN)...19/755 PM.

***UPDATE***

Minor updates this evening mainly for cloud cover as the marine
layer held fairly steady near 2500 feet through the afternoon, but
has surged across many of the Ventura County valleys and is bumping
up against the San Gabriel Mountain foothills in the San Fernando
and San Gabriel valleys. Onshore pressure gradients LAX-DAG
reached an impressive +10 mb this afternoon and had not weakened
much for several hours. Gusty west winds of 35-40 mph were common
through northern mountain slope/canyons and spilling out across
the Antelope Valley, where Palmdale gusted to 41 mph around 02Z.
Surface gradients weaken overnight, however, an approaching upper
trough to the north is generating some stronger winds aloft. This
keeps gusty W-NW winds going through the night across the I-5
corridor and across the eastern Ventura County and Los Angeles
County mountains. Wind advisories look on-track tonight and will
likely be able to let the Antelope Valley advisory expire in the
next few hours.

Low clouds cleared to about the Santa Barbara Airport earlier in
the afternoon, but an eddy over the channel has pushed clouds
westward toward Gaviota and they will likely continue to wrap
around Pt. Conception and northward along the west Santa Barbara
County coast overnight. Model HREF and NBM cloud guidance both
have clouds to Santa Maria late tonight and possibly making it
near San Luis Obispo by morning. Expect the marine layer to
continue to deepen another thousand feet or so by Friday morning
with another cooler than normal day for most areas west of the
mountains. Winds will not be as strong with the LAX-DAG gradient
about 3 mb weaker for Friday afternoon. It will be another tough
day to see much clearing from Santa Barbara southward with patchy
drizzle likely to occur in the morning hours.

***From Previous Discussion***

Areas south of Pt Conception now firmly in May Gray conditions.
Marine layer still around 2500` but expected to deepen tonight to
around 3500`. Strong onshore trends and gradients as well as an
approaching trough are helping to counter the typical afternoon
clearing processes and clouds so far pretty socked in along the
coast from Pt Conception all the way to the MX border and beyond.
Probably even cloudier tomorrow south of Pt Conception. Gradients
expected to be 3-4 mb weaker but with the deepening trend tonight
from the trough and likely some drizzle or very light rain in the
morning clouds may not even clear out of some of the coastal
valleys. So look for temps tomorrow to be well below normal for
all areas except the far interior. Marine layer expected to push
well into the valleys, lower coastal slopes, and could even get to
the edge of the Antelope Valley through the Highway 14 corridor.
Typical breezy west winds in the AV again Friday but should be
quite a bit weaker than today and tonight.

The Central Coast so far staying clear as northwest flow offshore
continues. However, those will be weakening some Friday into
Saturday and there should be increasing low clouds and fog there
in the next day or two, possibly as early as Friday morning as far
north as Santa Maria. Temps there should be near to slightly below
norms.

Big offshore trends Saturday following the passage of the trough
to the north and east. Gradients to the east aren`t expected to
actually go offshore but significant weakening of the onshore flow
should help provide earlier clearing to most areas except possibly
the immediate coast. Marine layer depth still expected to be
around 3500` but warming aloft during the afternoon should help
squash that somewhat and help the clearing trend. A little warming
expected with earlier sunshine but still well below normal for the
valleys especially. AV should again see a period of northeast
winds before shifting back to west in the afternoon.

The back and forth gradient trends continue Sunday as strong
onshore gradients return. However, rising heights should lower the
marine layer depth and at least help inland areas warm up 3-6
degrees from Saturday. And with decent subsidence in the boundary
layer most coastal areas should clear out by early afternoon.

.LONG TERM (MON-THU)...19/154 PM.

Ensembles continue to lean strongly towards a warming trend
through the middle of next week. While there are a few members
showing temps close to 100 by Wednesday in the valleys, a vast
majority of the solutions are in the mid 80s to mid 90s. Moderate
to strong onshore flow will keep temps closer to normal near the
coast with likely a shallow marine layer in place. Typical breezy
winds in the Antelope Valley with low humidities each day but so
far no signs of any Sundowner winds in the Santa Barbara area next
week. In fact, the SBA-BFL gradient rises to over 9mb next week
according to the GFS with slight to moderate southerly flow aloft,
so the marine layer may have a tough time clearing along south
facing beaches again next week.

&&

.AVIATION...19/1753Z.

At 17Z, the marine layer at KLAX was 2600 feet deep. The top of
the inversion was at 3600 feet with a temperature of 22 deg C.

Moderate confidence overall in the 18Z TAFs. Low clouds with
IFR/MVFR cigs were affecting coast and vly TAFs south of Point
Conception at TAF start time, but should clear from KBUR and KVNY
by 19Z. Clearing is also expected at KSBA, KCMA and KSMO by 23Z.
The rest of the coastal airfields will continue to have MVFR cigs
thru the day. Low clouds should return to all coastal and valley
areas south of Pt Conception this evening. Conditions should be
mostly MVFR, except IFR at some airfields for a while tonight.
There should be clearing to VFR by 17Z Fri for KVNY and KBUR
while coastal airfields will remain under MVFR cigs. The timing of
either clearing or onset of low clouds may be off +/- an hour or
two.

For airfields N of Point Conception, VFR conditions are expected
thru the TAF period except for KSMX which has a 20%-30% of IFR
conds late tonight into Fri morning.

For KWJF and KPMD, VFR conditions will prevail thru the TAF
period, altho with strong and gusty W winds there may be brief
periods of reduced vsbys at times this afternoon due to blowing
dust and sand.

KLAX...Moderate confidence in 18Z TAF. MVFR cigs are expected thru
the TAF period, altho there is a 20% chance of the low clouds
scattering out this afternoon. There is a 70% chance of east to
southeast winds exceeding 8-10 knots from 11Z-16Z Fri.

KBUR...Moderate confidence in 18Z TAF. VFR conditions are expected
this afternoon with a return of low clouds and MVFR conds 03Z-17Z.
The timing of the onset and dissipation of the low clouds may be
off +/- an hour or so.

&&

.MARINE...19/636 PM.

For the Outer Waters, moderate to high confidence in current
forecast. Tonight through Friday night, high confidence in Gale
force winds across PZZ670/673 (especially western sections) with
conditions generally remaining below Small Craft Advisory (SCA)
levels across PZZ676. For Saturday through Tuesday, high
confidence in SCA level winds across PZZ670/673 and the northwest
portion of PZZ676. Additionally, there is a 30-40% chance of Gale
force winds across PZZ670/673 Saturday afternoon through Sunday.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Tonight through Friday night, high
confidence in SCA level winds, especially during the afternoon and
evening hours. On Saturday, high confidence in winds and seas
remaining below SCA levels. For Sunday and Monday, there is a 60%
chance of SCA level winds, especially during the afternoon and
evening hours. For Tuesday, high confidence winds and seas
remaining below SCA levels.

For the Inner Waters south of Point Conception, high confidence in
current forecast. Tonight through Tuesday, winds and seas will
remain below SCA levels.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 6 AM PDT Friday for zones
      53-54. (See LAXNPWLOX).
     Wind Advisory in effect until 10 PM PDT this evening for zone
      59. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Saturday for
      zone 645. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Saturday for zones
      670-673. (See LAXMWWLOX).

&&

$$

PUBLIC...EB/MW
AVIATION...Sirard
MARINE...RAT
SYNOPSIS...MW/Hall

weather.gov/losangeles

Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox

NWS LOX Office Area Forecast Discussion