Area Forecast Discussion
Issued by NWS Los Angeles, CA

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093
FXUS66 KLOX 231022
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
322 AM PDT Wed Aug 23 2017

.SYNOPSIS...

A weak trough of low pressure west of Point Conception will
slowly move east through Thursday, while weakening. Strong high
pressure over the Borderland region of New Mexico this morning
will build northwest into Great Basin between Friday and Saturday
and bring a significant warming trend to the region through much
of next week.

&&

.SHORT TERM...(TDY-FRI)

A more entrenched marine layer stratus deck is developing this
morning as a weak trough of low pressure centered about 280 miles
west of Los Angeles, or near 34.5 and 123W edges closer to the
area. A marine layer depth around 1600 feet from the latest AMDAR
soundings from KLAX should deepen to near 2100 feet later this
morning, possibly deepening a bit more tonight and into Thursday
morning. The trough center will move into the Southern California
Bight on Thursday, while weakening. Temperatures will range near
seasonal normals the next couple of days, then start to warm on
Friday as the trough gets absorbed by a strong ridge of high
pressure over the Borderland region of New Mexico.

A few cloud build-ups cannot be ruled out over the next couple
afternoons and evenings. Marginal instability and moisture will
exist through Thursday, then drier air aloft should push in.

.LONG TERM...(SAT-TUE)

Ridging aloft over Southern New Mexico and Northern Chihuahua
this morning will build across the Desert Southwest between
Friday and Saturday and settle into the Great Basin. A
significant warming trend is becoming more likely for Sunday
through Wednesday. The main focus of the forecast was paid to the
developing heatwave next week. Model solutions are impressive
warming 950 mb temperatures up to 35-40 degrees Celsius across the
area for an extended period beneath a 594 dm heights. Forecast
temperatures are on the cool side of local temperatures studies
for the region, but if model parameters verify as progged
currently, valleys, foothill, and desert afternoon high
temperatures warming into the 100-110 degree range could come
into play. An excessive heat watch may be needed over the coming
days, if this pattern continues to remain consistent.

While the forecast maintains a dry stance for early next week, the
ridge position would be consistent with the possibility of a
window opening for monsoonal flow to enter at some point. GFS
model solutions, though inconsistent run-to-run, are entertaining
some possibility of monsoonal moisture slipping into the region
with a moist easterly flow for the beginning half of the work week
next week. PoPs have nudged higher for now, but future shifts
will likely need to iron out this wrinkle in the forecast.

&&

.AVIATION...23/1010Z.

At 0930Z, the marine inversion at KLAX was based at 1400 feet. The
top of the inversion was 3500 feet with a temperature of 23
degrees Celsius.

Overall, moderate confidence in 12Z TAF package. Current CIGs
should dissipate between 16Z and 20Z with VFR conditions for all
sites this afternoon. For tonight, high confidence in return of
stratus/fog to coastal and valley sites, but only moderate
confidence in timing (+/- 2 hours of current arrival forecasts).

KLAX...moderate confidence in 12Z TAF. MVFR CIGs could linger as
late as 20Z. For tonight, high confidence in return of MVFR CIGs,
but only moderate confidence in timing (+/- 2 hours of current 04Z
forecast).

KBUR...moderate confidence in 12Z TAF. There is a 30% chance that
VFR will prevail this morning. For tonight, moderate confidence
in return of IFR CIGs as well as timing (+/- 2 hours of current
08Z forecast).

&&

.MARINE...23/200 AM.

For the Outer Waters, good confidence in current forecast. Winds
and seas will remain below Small Craft Advisory (SCA) levels
through tonight. On Thursday, northwest winds will increase to
SCA levels and remain at SCA levels through Saturday. On Sunday,
winds should diminish below SCA levels.

For the Inner Waters, good confidence in current forecast. For the
waters north of Point Sal, winds and seas will remain below SCA
levels through tonight. On Thursday and Friday, northwest winds
will increase with SCA level winds likely each afternoon and
evening. For Saturday and Sunday, winds are expected to drop
below SCA levels. For the waters south of Point Conception, winds
and seas will remain below SCA levels through Sunday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK...(FRI-TUE)

A heatwave will likely develop this weekend and into the early
half of next week.

&&

$$

PUBLIC...Hall
AVIATION...Thompson
MARINE...Thompson
SYNOPSIS...Hall

weather.gov/losangeles



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