Acton Weather

000
FXUS66 KLOX 021622
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
922 AM PDT Tue Jun 2 2020

.SYNOPSIS...02/922 AM.

A slow moving low pressure system to the south will keep skies
partly to mostly cloudy through early Wednesday. Temperatures will
warm in most areas both today and Wednesday, but will abruptly end
Thursday and Friday as onshore flow and the marine layer returns.
Gusty northwest winds are expected for the weekend and warming
temperatures into early next week.

&&

.SHORT TERM (TDY-THU)...02/920 AM.

No updates needed this morning. High clouds continue to pour in
from the south ahead of an upper low to our southwest. Coverage
will vary from overcast to mostly sunny at any given time and
location. The air mass is definitely warmer today and gradients
are less onshore than yesterday so absent the clouds it would
definitely be a warmer day today. And by the end of the day most
areas should still be slightly warmer but the variable cloud
coverage will certainly play a role in the temps today. One area
that may end up slightly cooler is srn SB County as northerly flow
there is 1-2mb weaker than yesterday so there won`t be as much
downsloping flow there to boost temps.

Still not seeing any history of convection with this system.
Model soundings indicate some instability but like with the
moisture it`s very high based, mostly above 12000` so will not be
introducing any thunderstorms to the forecast unless we start
seeing some strikes developing.

***From Previous Discussion***

A 571 DM upper low 400 miles SW of LA will spin in place through
Thursday. Hgts will rise today and Wednesday as a ridge currently
over the NM/AZ state line will push to the west.

The upper low has entrained a large amount of mid and high level
clouds and skies will be partly to mostly cloudy today and
through Wednesday morning. There will be some clouds but they
will, for the most part, be confined to the Central Coast and
perhaps portions of southern LA county.

Onshore gradients both to the north and east are trending offshore
and will be near neutral on Wednesday morning. The rising hgts and
weaker onshore flow will bring 3 to 6 degrees of warming to the
area today with isolated 5 to 10 degrees of warming across the
Central Coast and the Santa Ynez (the SMX-BFL grad has the
greatest offshore trends today). Wednesday will be the warmest day
of the next 7 as the hgts peak and weakest onshore flow combine
with the increased sunshine to bring another 4 to 8 degrees of
warming to the area. Max temps temps on Wednesday will mostly be
10 to 15 degrees above normal except in the vlys where they will
be 15 to 20 degrees warmer than average. There will likely be some
100-101 degree readings in the vlys Wednesday afternoon.

The extra sunshine over the mtns on Wednesday will destabilize the
air over the mtns and if there is enough mid level moisture left
over a TSTM could develop but it is more likely that there will
just be some ACCAS.

The warm up will reverse on Thursday. The onshore grads will
strengthen Wednesday night and a weak eddy will spin up. Low
clouds will likely develop over the LA county coast. Hgts will
fall as well. Max temps will fall 3 to 6 degree but will remain
above normal.

.LONG TERM (FRI-MON)...02/318 AM.

The upper low finally makes its move starting Thursday night. The
increasing cyclonic flow will spin up a decent eddy and low clouds
and fog will spread across the coasts and work their way into the
lower vlys as well. The GFS forecasts an afternoon onshore push of
10 MB to KDAG which would result in limited clearing the EC only
has about half of that which would result in much better clearing.
For now went with the sunnier EC soln but this forecast could
change. The upper low will then pass to the south of the area
during the day. It seems like both mdls have been forecasting some
small chc of rain on one run and then none on the next. The south
of LA county trajectory has been consistently forecast and this
is more than likely a dry one so the forecast is dry. The onshore
flow falling hgts and deep marine layer will all combine to drop
max temps 6 to 12 degrees and almost all areas will end up with
below normal max temps esp the interior.

Broad troffing will cover the entire west coast over the weekend.
It will generate pretty strong NW flow. This along with increasing
offshore flow from the north to the south will likely bring
advisory level winds to srn SBA County, the I-5 corridor and the
Antelope Valley. The north push will likely limit the marine layer
stratus to the LA coast and western SBA county. Rising hgts and
the north offshore push will bring a few degrees of warming each
day.

Late Sunday sfc high pressure is forecast to build into NV and set
up offshore flow both from the north and the south. If this day
seven forecast comes true skies will be clear and max temps will
continue to warm esp in the vlys. There will be some NE canyon
winds in the morning.

The rest of next week continues to look warmer than normal.

&&

.AVIATION...02/1615Z.

At 1540Z, the marine inversion at KLAX was based at 600 feet.
The top of the inversion was 2000 feet with a temperature of
21 degrees Celsius.

Overall, moderate to high confidence in 18Z TAF package. High
confidence in VFR conditions through TAF period for most sites.
Only exceptions will be KSBP and KSMX where there is moderate
confidence, at best, in development of LIFR/VLIFR conditions
overnight.

KLAX...High confidence in 18Z TAF as VFR conditions are
anticipated through TAF period. No significant easterly wind
component is expected.

KBUR...High confidence in 18Z TAF as VFR conditions are
anticipated through TAF period.

&&

.MARINE...02/915 AM.

For the Outer Waters, moderate to high confidence in current
forecast. High confidence in Small Craft Advisory (SCA) level
winds across PZZ673/676 through tonight with conditions below SCA
levels across PZZ670. For Wednesday through Saturday, there is
a 60-70% chance of SCA level winds across all the Outer Waters,
especially during the afternoon and evening hours.

for the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. High confidence in winds and seas
remaining below SCA levels through Thursday. On Friday and
Saturday, there is a 30-40% chance of SCA level winds during the
afternoon and evening hours.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. High confidence in winds and seas
remaining below SCA levels through Friday. On Saturday, there is
a 30-40% chance of SCA level winds across western sections,
especially during the afternoon and evening hours.

&&

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

&&

.HAZARD POTENTIAL OUTLOOK (THU-MON).

Gusty northwest winds are possible in southern SB County and the
I5 corridor and Antelope Valley Saturday through Monday.

&&

$$

PUBLIC...MW/Rorke
AVIATION...RAT
MARINE...RAT
SYNOPSIS...MW

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