Duarte Weather

000
FXUS66 KLOX 281816
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1116 AM PDT Tue Sep 28 2021

.SYNOPSIS...28/403 AM.

Today will be cool as a dry cold front moves through the region.
Gusty north to northwest winds will be likely across southern
Santa Barbara County and the Interstate 5 corridor through
tonight. A significant warming trend with weak offshore flow is
expected from Wednesday into this weekend.

&&

.SHORT TERM (TDY-THU)...28/859 AM.

A deep marine layer (around 2600 ft at LAX) helped to push
extensive marine layer clouds and patchy drizzle from the coast
and vlys up to the lower coastal slopes over VTU/L.A Counties
early this morning. The marine inversion was a bit shallower N of
Point Conception but low clouds were fairly extensive over the
SBA County Central Coast, Santa Ynez Vly and SLO County interior
vlys. Northerly flow also helped to develop low clouds over the N
slopes of the mtns and into the Cuyama Vly early this morning. A
dry cold front will push through the forecast area today. This
will help to bring in a cooler airmass to the region and break up
the marine inversion, with the low clouds expected to dissipate
through about midday, except some low clouds should remain banked
up on the N slopes. Once the low clouds clear away, there will be
mostly sunny skies thru the rest of the day. Temps will be much
cooler today for the far interior vlys, mtns and deserts, and
actually a bit warmer for the L.A./VTU County interior coastal
areas and vlys thanks to more sunshine this afternoon. Still,
high temps today will be 5-10 deg below normal across the entire
forecast area. The warmest inland coastal areas, vlys and lower
mtns should top out in the 70s today.

There were strong and gusty NW to N winds this morning mainly in
the mtns along the I-5 corridor into the Antelope Vly, with Wind
Advisories in effect for the L.A./VTU County Mtns until late this
morning, and across the deserts until this evening. Gusts up to
45 mph are expected. Gusty sub-Advisory NW to N winds were also
noted across southern SBA County mainly W of Goleta this morning.
These winds should diminish some into this afternoon. Otherwise,
breezy NW to N winds should prevail over much of SLO/SBA Counties
into the L.A./VTU County mtns thru the afternoon.

An upper level trof along the central and nrn CA coast this
morning will push S into the forecast area this afternoon before
moving E of the region tonight. An upper level ridge will move
into the E Pac on Wed then start to build into CA Wed night and
Thu, with a broad NW-N flow aloft and H5 heights increasing to
584-585 dam by late Thu.

Offshore pressure gradients and trends to the N and E will
increase tonight and Wed. Across SBA County, the SBA-SMX and SBA-
BFL gradients will decrease significantly tonight which will help
strong and gusty winds develop below and thru the passes and
canyons, and Wind Advisories are expected for these areas. Gusty
NW winds will also prevail across the L.A./VTU County mtns
tonight, especially along the I-5 Corridor, and additional Wind
Advisories may be needed. Breezy offshore flow can be expected
Wed morning for many areas, then stronger offshore flow can be
expected later Wed night and Thu morning, with winds shifting from
N Wed night to NE Thu morning. It looks like the strongest winds
by Thu morning will be over the favored areas of VTU/L.A.
Counties, with local gusts to Advisory levels possible especially
in the foothills. There should also be breezy to gusty NE to E
winds over portions of SLO/SBA Counties by Thu morning,
particularly along the SLO County Coastal Range.

It looks like marine layer clouds should linger along the L.A.
County coast into the adjacent vlys tonight into Wed morning.
Otherwise, the increasing offshore flow will push any leftover
marine layer clouds well off the coast Wed thru Thu with mostly
clear skies prevailing across the region. The offshore flow and
warming boundary layer/950 mb/850 mb temps will combine to warm
surface temps up considerably over the next couple of days. It
will still be a few degrees below normal for most areas on Wed
with the warmest vlys and lower mtns expected to reach the upper
70s to lower 80s. Temps on Thu should warm further to 5-10 deg
above normal for most areas away from the coast. The warmest areas
from the inland coast to the vlys should top out in the upper 80s
to lower 90s. The deserts should be near normal on Thu with highs
in the lower to mid 80s.

.LONG TERM (FRI-MON)...28/400 AM.

Offshore flow is expected to continue on Friday, although weaker
than Thursday. This should lead to another hot, summer-like day
across the area with temperatures in the 80s and 90s away from the
beaches. The marine layer will once again be absent and there will
be full sunshine.

A cutoff low breaks from the main flow off the coast of Central
California and hangs out over the ocean over the weekend. It
won`t really affect our weather, but the increasing cyclonic flow
will likely allow the marine layer to make a comeback and bring
stratus back to the Central Coast and possibly the LA and Ventura
County coastal areas. Temperatures will remain hot through the
weekend then cool through next week.

&&

.AVIATION...28/1814Z.

At 1724Z, the marine layer was around 3000 feet deep at KLAX.
The top of the inversion was around 6200 feet with a temp of 15C.

Widespread low clouds in most coastal and valley areas south of
Point Conception early this morning. Conds were mostly MVFR,
except IFR to VLIFR in the foothills and mtns, and portions of the
Central Coast, Expect rather slow clearing today, and skies may
remain mostly cloudy all day in some areas. However, expect cigs
to rise into the VFR category, with the exception of in the
foothills and mtns, where IFR cigs may persist. Expect low clouds
to affect coastal and possibly some valley areas of L.A. County
tonight, with generally MVFR conds, except IFR conds in the
foothills.

KLAX...Low confidence in the 18Z TAF. There is a 20-30% chance
that cigs will remain MVFR well into the afternoon. There is a
30% chance that skies will remain clear tonight.

KBUR...Low confidence in the 18Z TAF. MVFR conditions will linger
through much of the period. There is a 30% chance that MVFR cigs
could linger well into the afternoon. There is a 30% chance that
marine clouds will reform tonight.

&&

.MARINE...28/840 AM.

No changes to the marine forecast in the morning update.

For the waters outer waters, moderate to high confidence that
winds will increase to Gale Force later this morning, then
continue thru late tonight. Small Craft Advisory level winds and
seas are expected from late tonight thru late Wed night. There is
a 30% chance that SCA conds will continue on Thu. SCA conds are
not expected Thu night thru Sat.

Across the inner waters north of Pt. Sal, fairly good confidence
in SCA level NW winds this afternoon/evening, and again Wed
afternoon/evening. There is a 30-40% chance that seas will remain
above SCA levels thru at least late tonight or possibly even thru
Wed morning, so the SCA may have to be extended. SCA conds are
not expected Thu thru Sat.

For the SBA Channel, moderate to high confidence in SCA level W-NW
winds this afternoon and evening, mainly across western sections.
There is a chance that SCA conds could linger thru late tonight.
SCA conds are not expected Wed thru Sat.

Across the southern inner waters, there is a 30-40% chance of SCA
level winds this afternoon/evening across northern/western portions,
mainly near Anacapa Island. There will be rough and choppy seas
thru tonight. Otherwise, SCA conds are not expected thru Sat.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 9 PM PDT this evening for zone
      59. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
      for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 9
      PM PDT this evening for zone 650. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Wednesday for zones
      670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (THU-MON).

Gusty northeast winds are possible Thursday across Los Angeles and
Ventura Counties. Temperatures will warm to near heat advisory
levels Thursday through Sunday. There will also be elevated to
brief critical fire weather concerns Thursday through Sunday.

&&

$$

PUBLIC...Sirard/Stewart
AVIATION...Sweet/DB
MARINE...Sweet/DB
SYNOPSIS...Stewart

weather.gov/losangeles

NWS LOX Office Area Forecast Discussion