Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 231654
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
954 AM PDT Tue May 23 2017

.SYNOPSIS...
A low system will approach by midweek to spread the night to morning
marine layer farther inland. The temperatures will drop on Wednesday
and go below the seasonal normals from Thursday to Saturday. A high
will build in over the weekend with temperatures to reach above the
seasonal normals by early next week.

&&

.SHORT TERM...(TDY-THU)

Another shallow marine lyr this morning with a strong low lvl
inversion based at around 1000 ft. Overall scenario not too
dissimilar from yesterday, though both the NKX and VBG soundings
show slight warming above the marine lyr which models did pick up
on yesterday. So while coastal area temps will likely be about
the same, inland areas (mainly above 1000-1500 ft elevation) will
warm a degree or two. Remainder of the forecast looks on track as
well. Still not enough moisture to go with any thunderstorms
Wednesday but still worth keeping a close eye on. Then a deep
marine lyr and significant cooling for the end of the week.

***From previous discussion***

A little deeper marine layer tonight with a little better onshore
flow will bring stratus into the lower vlys tonight.

A trof will move into the area during the day Wednesday. Onshore
flow will really pick up as well. The increased onshore flow will
again prevent much in the way of beach clearing. There is a good
amount of instability and CAPE over the mtns in the afternoon.
There is however little to no moisture in the lower levels so
expect some CU build ups in the afternoon but no showers. Above
normal onshore flow to the east will make for a breezy afternoon
in the Antelope vly.

Lots and lots of stratus Wednesday night as the moderate onshore
flow combines with the lowering hgts and cyclonic flow of the
upper trof. Look for the marine layer to deepen to 4000+ feet and
for the stratus to push through the coasts over the vlys and deep
into the mtns passes and coastal slopes. The interior of SLO
county will even be covered in clouds. There will be a pretty good
chc of drizzle near the foothills due to the orographic lift.

10+ mb of onshore flow to the east and 7 mb to the north on
Thursday. This along with a 4000 foot marine layer will keeps
skies mostly cloudy for most of the day across almost all of the
coasts and vlys. Max temps will be in free fall and will be 10 to
15 degrees blo normal. Its hard to imagine a scenario where a 10+
mb onshore push does not generate advisory level winds across the
Antelope Vly.

.LONG TERM...(FRI-MON)

Not much change in the meteorological parameters on Friday and
expect a do over day.

A ridge moves into the area for the holiday weekend. It will bring
increasing hgts which will smoosh the marine layer down and out of
the vlys as well as decreasing onshore flow which will enable
earlier clearing. Look for a three day trend of lessening clouds
and increasing temps. Max temps will climb back to normal on
Sunday and then exceed normals on Monday.

&&

.AVIATION...23/1110Z...

At 0900Z, the marine inversion at KLAX was based at 1200 feet. The
top of the inversion was 2100 feet with a temperature of 25
degrees Celsius.

Overall, moderate confidence in 12Z TAF package. For coastal
sites, current IFR/LIFR conditions should dissipate by afternoon.
For tonight, high confidence in return of IFR conditions to
coastal sites, but only moderate confidence timing. For valley
and desert sites, VFR conditions should prevail through the
period.

KLAX...moderate confidence in 12Z TAF. There is a 50% chance that
conditions remain VFR this morning. For tonight, high confidence
in return of IFR conditions, but only moderate confidence in
timing (+/- 2 hours of current 01Z forecast).

KBUR...high confidence in 12Z TAF. There is a 20% chance of
IFR/MVFR conditions developing after 10Z.

&&

.MARINE...23/900 AM...

For the Outer Waters, moderate confidence in current forecast.
Winds will diminish below Small Craft Advisory (SCA) levels this
morning. Winds and seas are expected to remain below SCA levels
through Friday (although there is a 30% chance of SCA level winds
this afternoon and again Wednesday afternoon). By Saturday, there
is a good chance of winds increasing to SCA levels.

For the Inner Waters, high confidence in current forecast. Winds
and seas are expected to remain below SCA levels through Friday.
On Saturday, there is a good chance of winds increasing to SCA
levels in the afternoon/evening hours.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK...(THU-MON)
Advisory level southwest winds are possible Thursday through
Friday across the mountains and deserts.

&&

$$

PUBLIC...MW/Rorke
AVIATION...Thompson
MARINE...Sweet
SYNOPSIS...STu

weather.gov/losangeles



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