378 
FXUS66 KLOX 072113
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA 
213 PM PDT Fri Sep 7 2018

.SYNOPSIS...07/1253 PM.

A high will bring above normal temperatures into Monday, with the 
peak on Saturday. The weak onshore flow will limit the overnight 
marine layer to the coast into Monday, otherwise fair skies. A low
should arrive by Tuesday for at or below normal temperatures and 
overnight clouds, fog and patchy drizzle into Friday.

&&

.SHORT TERM (TDY-MON)...07/206 PM.

The late week warm up has begun as onshore flow has weakened and
the ridge aloft has strengthened. The LAX profiler is showing a
lowering marine layer depth this afternoon, down to around 1000'
and gradients are expected to weaken further Saturday. So
everything is pointing towards a big increase in temps tomorrow 
which should be the warmest day of the next week. Looking back at 
some historical temperature data highs Saturday should easily top 
100 across the warmer valleys and possibly as high as 106. Across 
the inland coastal plain highs should get into the lower 90s. This
likely won't break any records as the records are generally above
108 in the valleys, lower 100s at Downtown LA, and lower 90s at 
the beaches. Paso Robles probably has the best shot with a record 
of 105. One could make a case for a heat advisory tomorrow for 
some of the valleys, especially the San Fernando, and the 
mountains but unless highs go far beyond the current forecast it's
too marginal of a case. Marine layer stratus, which is still 
stubbornly hugging the coast, is expected to be confined to 
coastal LA County and the Central Coast by Saturday morning.

A cooling trend will begin Sunday as a trough in the Pac NW starts
to flatten the ridge and gradients trend onshore. Temps will still
be well above normal but a couple degrees cooler than Saturday.
More cooling on tap for Monday with highs dropping back down to
near normal levels. Low clouds will become more widespread each
day.

An increase in northerly flow tonight and again Saturday will
result in some breezy winds across srn SB County but should be
below advisory levels.

.LONG TERM (TUE-FRI)...07/213 PM.

Model agreement continues to improve next week as the ECMWF has
trended weaker with the trough next week and now actually shows
the high building back stronger from the southeast than the GFS by
late next week. In the meantime, increasing onshore flow with
lowering heights aloft will continue the cooling trend through at
least the middle of next week with low clouds pushing into the
valleys. After that the trends are still uncertain but it looks
like models are favoring a slight rebound in temps Thu/Fri.

&&

.AVIATION...07/1709Z.

At 1515Z, the marine inversion at KLAX was based at 1600 feet. 
The top of the inversion was 3900 feet with a temperature of
27 degrees Celsius.

Overall, moderate confidence in 18Z coastal TAFs and high
confidence in valley/desert TAFs. Current IFR/MVFR conditions
along coastal sites should dissipate by early this afternoon. For
tonight, inversion will be shallow enough to confine stratus to 
coastal sites, but low confidence in timing of return.

KLAX...moderate confidence in 18Z TAF. High confidence in VFR
conditions through this evening. For tonight, high confidence in
return of IFR conditions, but low confidence in timing (could be
+/- 4 hours of current 07Z forecast).

KBUR...high confidence in 18Z TAF. There is a 20% chance of MVFR
VSBYs 10Z-16Z.

&&

.MARINE...07/1240 PM.

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) level winds will develop today and will
continue through Wednesday. There is a 30% chance of GALE force 
gusts at times across the outer waters Monday and Tuesday.

For the inner waters north of Pt. Sal, there is a 70% chance of 
SCA level winds each afternoon and evening from Saturday through
Wednesday. 

For the inner waters south of Pt. Conception, conditions are 
generally expected to remain below SCA levels thru Wednesday. 
There is a 30% chance of SCA level winds each evening Saturday
through Tuesday across the western half of the Santa Barbara
Channel.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Monday for
      zones 670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (MON-FRI).

No significant hazards expected.

&&

$$

PUBLIC...MW
AVIATION...RAT
MARINE...RAT
SYNOPSIS...STu

weather.gov/losangeles