Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 221709

1009 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 0900Z, the marine inversion at KLAX was based at 900 feet. The
top of the inversion was 3300 feet with a temperature of 22
degrees Celsius.

Overall, moderate to high confidence in 12Z TAF package. Moderate
to high confidence in VFR conditions through this evening (with a
30% chance of IFR CIGs 12Z-17Z at coastal TAF sites). For tonight,
moderate confidence in return of IFR conditions to coastal sites,
but low confidence in timing.

KLAX...moderate confidence in 12Z TAF. There is a 30% chance of
IFR CIGs 12Z-17Z. For tonight, moderate confidence in return of
IFR CIGs, but low confidence in timing (could be +/- 4 hours of
current 08Z forecast).

KBUR...high confidence in 12Z TAF. There is a 20% chance of IFR
conditions developing after 08Z tonight.


.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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