Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 290137
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
637 PM PDT Sun May 28 2017

.SYNOPSIS...
A weak ridge building aloft will support a warming trend through
early next week. The ridge will be replaced by a weak trough aloft
by the middle of next week providing a cooling trend with more
widespread night to morning low clouds. There is also a slight
chance of thunderstorms across the mountains Wednesday.

&&

.SHORT TERM...(SUN-WED)

The latest water vapor imagery indicates a ridge of high pressure
over the state this afternoon. Weakening onshore flow across the
area has brought some warming this afternoon. A weak marine
inversion the last couple of days should strengthen and allow for
better marine layer stratus formation tonight and into Memorial
Day. Despite weaker onshore flow, the marine layer depth near 700
feet deep currently should deepen to around 1500 feet deep by
Monday morning.

A trough of low pressure near 34N and 130W will approach the area
through Monday as the ridge of high pressure nudges east. This
trough in phase with a broader trough over the Eastern Pacific
Ocean will become a staple of the weather pattern through the
middle of next week. After near similar day for Memorial Day in
comparison to today, a cooling trend should develop into midweek
along with a deepening marine layer.

Model solutions are introducing the possibility of some
instability developing over the mountains for tomorrow and there
is some concern about convective storms developing over the
mountains for the Memorial Day holiday. Models solutions look to
introduce some cumulus formation in moisture fields. There is some
omega and CAPE values over the mountains, especially the Ventura
County portion. While this is a rather new wrinkle in the
forecast, some clouds have been added to the package. PoPs have
also been nudged higher, but remain below mentionable thresholds.
The next shift will be briefed about the possibility of
convection.

.LONG TERM...(THU-SUN)

A trough of low pressure will likely linger along the West Coast
into Thursday. Increased onshore flow and a deeper marine layer
will likely continue cooling into Thursday. Patchy night through
morning drizzle or light showers cannot be ruled out between late
Tuesday night through Thursday morning, especially in the
foothills and mountains. A mention of a slight chance of showers
and thunderstorms has been left in place for the mountains on
Wednesday afternoon and evening, but the possibility of night
through morning drizzle will likely need to be addressed.

A brief warm-up should develop for Friday, but model solutions are
handling a developing trough of low pressure to the southwest of
the area poorly for next weekend. The forecast takes a cooler
stance for now as higher confidence exists in a continued strong
onshore flow pattern.

&&

.AVIATION...29/0030Z...

At 2330Z, the marine inversion at KLAX was based at 900 feet. The
top of the inversion was 2750 feet with a temperature of 22
degrees Celsius.

Overall, Low to moderate confidence in 00Z TAF package. N. of
Point Conception, pretty confident with 00z TAFs in respect to
timing and IFR category. Lower confidence with areal coverage and
timing. VFR conditions are anticipated through this evening.
Except the Central Coast will be affected by IFR cigs by late this
evening. For tonight, high confidence in return of stratus/fog to
Los Angeles coast and moderate confidence it will reach Ventura
County coastal sites as well after midnight. 40% chance it will
affect KSBA as well as KBUR and KVNY. Eddy not too strong to drive
the stratus to north into SBA south coast. Models indicate that
low MVFR cigs will linger along coastal areas most of the
afternoon. 40% chance that cigs along coastal tafs will linger +2
hours past 00z TAF times.

KLAX...moderate confidence in 00Z TAF. IFR to MVFR stratus should
develop between 07z-09z. Lower confidence with scour out times.
40% chance that cigs could linger into mid afternoon or around
22z.

KBUR...Low to moderate confidence in 00Z TAF in respect if stratus
will make it to the terminal. 40% chance that IFR cigs will occur
after 12z. 50% chance for MVFR vsbys after 09z. If stratus does
develop, it should scour out within an hour of 00Z taf.

&&

.MARINE...28/100 PM...

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) level winds will continue through Friday.
There is a 20% chance of Gale force conditions developing in the
afternoon/evening hours Tuesday and Wednesday.

For the Inner Waters, moderate confidence in current forecast. For
the waters north of Point Sal, SCA level winds are likely each
afternoon/evening today through Friday. For the waters south of
Point Conception, winds and seas are expected to remain below SCA
levels through Friday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 9 AM PDT Tuesday for
      zones 645-670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(WED-SUN)
No significant hazards expected.

&&

$$

PUBLIC...Hall
AVIATION...Kaplan
MARINE...Thompson
SYNOPSIS...Munroe

weather.gov/losangeles



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