Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 172348

448 PM PDT Thu Aug 17 2017

...Updated Aviation Discussion...

A low will bring overnight low clouds, with fog at times, to the
coast and some valleys, otherwise mostly clear into Saturday. The
low should deepen early next week and spread the overnight marine
layer farther inland with temperatures near normal. The low will
weaken by midweek for a temperature warmup into Friday.



After a day of minimal marine lyr today coverage should be better
tonight with a stronger inversion in place. Weak offshore trends
will continue into Friday so either little change or slight
warming expected tomorrow with highs near normal for the beaches
but slightly below normal elsewhere. Saturday should be almost a
carbon copy of Friday.

A trough along the west coast will deepen Sunday, leading to a
deeper marine lyr and a cooling trend. Could even see some patchy
drizzle during the morning hours. The presence of the upper low
aloft and a little bit of mid level moisture should generate some
afternoon clouds over the mountains but at this time there doesn`t
appear to be enough moisture to go with any thunderstorms.


The trough will deepen further Monday then weaken Tue-Thu with
some height/thickness rises. Forecast temps Monday still seem a
bit warm given the upper pattern and likely a fairly deep marine
lyr. Then slight warming through mid week but temps still a couple
degrees below normal.



At 2300Z, the marine layer depth was around 2200 ft deep at KLAX.
The top of the marine inversion was around 3400 ft with a
temperature near 20 degrees Celsius.

Moderate confidence in coastal forecast...low confidence in the
San Fernando Valley. At coastal terminals, there is a good chance
of low clouds arriving between 06z-09z tonight, with IFR to MVFR
conditions. There is a 40% chance that timing will differ by +/- 2
hrs from Taf times. The earliest arrival is likely for Central
Coast terminals, with later arrivals at coastal terminals south of
Point Conception. There is a 30 percent chance that KBUR and KVNY
will remain clear through the period.

KLAX...Moderate confidence in the 00z TAF. There is a 30 percent
chance that timing will differ by at least 2 hrs from taf times.
There is a 20 percent chance that low clouds remain in MVFR
category, or that cigs remain scattered overnight.

KBUR...Moderate confidence in the 00z TAF. There is a 30 percent
chance that VFR conditions persist through Friday afternoon.


.MARINE...17/200 PM.

Moderate to high confidence in the forecast. Winds should remain
below Small Craft Advisory levels through early next week. There
is a 40 percent chance of Small Craft Advisory conditions
developing on Friday afternoon and evening across the Southern
Outer Waters. There is 20 percent chance of Small Craft Advisory
conditions across the Santa Barbara and San Pedro Channels each
afternoon and evening through the weekend.




No significant hazards expected.



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