Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 221756

1056 AM PDT Tue Aug 22 2017

A low will bring an overnight coastal marine layer, otherwise mostly
clear skies into next week. The temperatures will be around normal
into midweek. Then a high will move in for a warming trend from
Friday into next week, with Monday and Tuesday the peak heat days.



Weakening onshore flow across the area has left the stratus
pattern in disarray this morning as a weak trough of low pressure
has pulled off the coast. Low confidence should be exercised in
the stratus forecast the next 24-36 hours as models have not
handled the moisture well. The trough of low pressure currently
located 33.5N and 124W, or about 325 miles west of Los Angeles
will slowly start to advance over the region through Thursday.
With onshore weakening substantially, today is shaping up to be
closer to normal than previously forecast. Temperatures have been
tweaked upward for today, especially along the coast. As the
trough draws closer to the area, it will weaken. 500 mb heights
will drop some but not as much as previously thought. A slight
cool down should occur for Wednesday, but not as drastic as
forecast the last several days. The marine layer depth, near 900
feet deep early this morning on KLAX AMDAR soundings, will deepen
somewhat through Wednesday morning. If NAM-WRF solutions play
out, a marine layer depth near 1300 feet seems more practical on
Wednesday morning.

The trough will slowly move ashore while weakening through
Thursday. Some minor warming back to normal will take place on
Thursday as the trough moves over the area, then the ridge will
absorb the trough on Thursday night.


Ridging aloft over the West Texas this morning will start to
build west into the Desert Southwest through Friday. The ridge
will engulf the remnant trough over Southeast California and wash
it out. 500 mb heights will start to climb and 1000-500 mb
thickness values will increase from Friday through the weekend.
Temperatures take a warm stance over forecast guidance, weighted
heavily in favor of local temperature studies. Temperatures look
to be warmest on Monday or Tuesday when the thermal trough pushes
west. The marine layer could get obliterated on these days when a
light offshore push displaces the marine layer and allows the
thermal trough to settle in. Temperatures could be somewhat
underdone for the beaches early next week as temperatures in the
lower to mid 80s could be common, except 70s along the Central
Coast beaches.



AT 1800Z, the marine inversion at KLAX was based at 950 feet. The
top of the inversion was 4200 feet with a temperature of 23
degrees Celsius.

Overall, moderate confidence in this TAF package. Moderate to
high confidence in VFR conditions through early this evening (03Z)
then low confidence after that due to advancing stratus from north
to south. KSBP and KSMX could be impacted ahead of schedule. From
03-10Z there is potential for IFR CIGS with patchy LIFR fog for
central coastal sites, and MVFR/IFR CIGS from 10-18Z for the
south coasts and valley sites.

KLAX...moderate confidence through 06Z then low confidence.
06-18Z there is a potential for IFR CIGS but timing could be +/-
2 hours of the 18Z forecast.

KBUR...high confidence through 08Z then low/moderate confidence.
There is potential for MVFR/IFR CIGS from 10-15Z but timing could
be +/- 2 hours of the 18Z forecast.


.MARINE...22/830 AM...

For the outer waters, good confidence in current forecast. Rather
smooth conditions through Wednesday, then northwest winds increase
late Wednesday night into Thursday. Small Craft Advisory (SCA)
levels possible then with building seas. SCA conditions may
continue into Saturday.

For the inner waters, good confidence in the current forecast. For
the waters north of Point Sal, winds and seas will remain below
SCA levels through Wednesday. On Thursday and Friday, SCA level
winds are likely each afternoon and evening with winds diminishing
below SCA levels on Saturday. For the waters south of Point
Conception, winds and seas are expected to remain below SCA levels
through Saturday.




A significant heatwave could develop this upcoming weekend and
continue into early next week.



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