Acton Weather

000
FXUS66 KLOX 062001
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
101 PM PDT Thu Aug 6 2020

.SYNOPSIS...06/1209 PM.

Night through morning low clouds and fog will continue across the
coasts and valleys through the week, then will begin to recede
toward the coast over the weekend. Cool temperatures will continue
then a gradual warming trend is expected to begin over the weekend.

&&

.SHORT TERM (TDY-SUN)...06/1251 PM.

Stagnant weather pattern the next several days with minimal
changes overall for another ten days or so. Upper level
troughiness remains along the west coast with weak to moderate
onshore pressure gradients. From Friday through about Monday
500mb heights increase only about 30m from 586 to 589dm. A deep
marine layer up to 3300 feet this afternoon will change very
little into Friday morning. Low clouds have been slow to move away
from all coastal areas today and expect a return of clouds and
patchy fog well inland through foothills and mountain canyons by
sunrise. This will help keep temperatures below normal for most
areas with coolest conditions near the coast and nearby valleys.

Only impactful weather over the next 24-hours, which is minimal,
are locally gusty southwest winds through gaps in terrain entering
the Antelope Valley from the mountains and locally gusty northwest
winds to 40 mph in the western canyons along the south SBA County
coast this evening near Gaviota.

Expect a slight warming trend later in the weekend and early next
week. We should gradually see less depth in the marine layer and
not as much inland low clouds during this time frame. High
temperatures will remain just below normal through the weekend,
maybe reaching normal by Monday.

.LONG TERM (MON-THU)...06/1254 PM.

Some model differences on either reinforcing the cool trough
pattern next week over CA or retrograding it westward. If the
later happens this would help heights build toward 591dm which
would mean less night/morning low clouds and more heating during
the day. For now it seems best to remain in a persistence
forecast with a continued trough pattern, but the ECM ensembles
are leaning toward the higher heights so we may need to increase
temperatures some next week. There will be a tropical cyclone
moving from the coast of Central America to well south of Baja
around Tuesday or Wednesday. See very little potential impacts
here except for a possible increase in surf conditions at times by
midweek.

&&

.AVIATION...06/1802Z.

At 1715Z at KLAX, the marine layer was 3300 ft deep. The top of
the inversion was around 4300 ft with a temp of 16 C.

Very low confidence in coastal and valley TAFs and high
confidence in desert TAFs. A rather deep marine layer (3000 ft on
the central coast, and 3300 ft down at KLAX) along with strong
northwest winds in the coastal waters have caused a change in the
marine layer evolution. Multiple cloud layers, multiple eddies
and a possible reverse clearing pattern with coastal sections
clearing before valleys have resulted in a more pessimistic
clearing forecast this afternoon. Some coastal and valley TAF
sites may not clear. Fortunately, most ceilings are in the MVFR to
VFR category.

The Antelope Valley TAF sites will have the usual gusty afternoon
winds.

KLAX...Very low confidence in the 18z TAF. There is a 50 percent
chance that ceilings will not clear. There is a 20% chance an 8
kt east wind component after 13z Fri.

KBUR...Very low confidence in the 18z TAF. There is a 50 percent
chance that ceilings will not clear.

&&

.MARINE...06/848 AM.

Morning update: Once again, the 12z NAM12 vastly increased the
winds for this afternoon and tonight in the outer waters, but
suspect that the winds may be overdone, so will keep the SCA for
now and just increase the wind speeds somewhat. Also, the inner
waters adjacent to the central coast will need a SCA for late this
afternoon through tonight.

From previous discussion...

Overall, moderate to high confidence in forecast. High confidence
that Small Craft Advisory (SCA) level winds will continue across
the outer waters along the Central Coast to San Nicolas Island
through Friday night, strongest during the afternoon and evening
hours. There is a 40% chance of SCA level winds reaching the
nearshore waters along the Central Coast this afternoon and
evening. On Saturday and through the weekend, good confidence that
winds and seas will be below SCA level across all the waters.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Friday for
      zones 645-670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (SUN-THU).

No significant hazards expected.

&&

$$

PUBLIC...EB
AVIATION...Sweet/Stewart
MARINE...Sweet/Stewart
SYNOPSIS...EB

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