Area Forecast Discussion
Issued by NWS Los Angeles, CA

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735
FXUS66 KLOX 301205
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
505 AM PDT THU JUN 30 2016

.SYNOPSIS...

A cooling trend is expected through the weekend as a weak trough
develops across the West Coast. Along with the cooling trend,
there will be rather widespread night and morning stratus and fog
across the coasts and coastal valleys. For the first half of next
week, high pressure will slowly build, resulting in a gradual
warming trend for the area.
&&

.SHORT TERM...(TDY-SAT)

Overall, 00Z models in good synoptic agreement through the period.
At upper levels, ridge will be replaced by a weak trough
developing over northern/central California. Near the surface,
onshore flow is forecast to gradually strengthen through the
period.

Forecast-wise, main concern in the short term will be the marine
layer stratus as well as temperatures. Current sounding data
indicates marine inversion running between 1000 and 1500 feet
while satellite shows stratus filling in across the coastal plain.
With the weak upper trough and increasing onshore flow, the marine
inversion should deepen over the next couple of days with stratus
and fog penetrating further inland to the coastal valleys. Each
afternoon, the stratus should dissipate nicely as the inversion
will likely not be too strong. Other than the marine layer
stratus, skies should remain mostly clear through the period.

As for temperatures, the increased marine influence as well as
lowering thicknesses will lead to a cooling trend through
Saturday. The most noticeable cooling will occur today and again
on Friday with only minor additional cooling on Saturday.
Temperatures on Friday/Saturday will generally be a couple degrees
below seasonal normals.

As for winds, the increasing onshore flow will likely generate
some gusty afternoon/evening southwesterly winds across the
mountains and deserts. However, at this time, there does not
appear to be any wind that would approach advisory thresholds.


.LONG TERM...(SUN-WED)

Overall, 00Z models remain on the same synoptic page through the
period. At upper levels, trough will disappear as a flat ridge
builds in from the east. Near the surface, moderate onshore flow
will continue (although slowly weakening from day-to-day).

Forecast-wise, nothing too exciting is anticipated into the middle
of next week. With the above synoptic pattern, the main issues
will continue to be the marine layer stratus and temperatures.
There will be some day-to-day variation in the areal coverage of
the stratus, but still should be plenty of night/morning stratus
in the coastal valleys each day. As for temperatures, there should
be a gradual warming trend, especially away from the beaches. At
this time, the mid-level flow looks to remain southwesterly which
should keep any monsoonal moisture to the east through Wednesday.


&&

.AVIATION...30/12Z...

At 0900Z, at KLAX, the marine layer depth was around 1400 feet.
The top of the inversion was at 3600 feet with a temperature of 30
degrees Celsius.

Widespread stratus is all coastal areas early this morning, with
generally IFR conds, except low MVFR conds across srn L.A. County
and LIFR conds across portions of the Central Coast. Clouds have
also pushed into the Santa Ynez and Salinas Valleys, with LIFR
conds, and may push into the San Gabriel Valley by daybreak.
Expect skies to clear in most areas by mid to late morning, except
possibly as late as early afternoon near the immediate coast.
Expect a slightly deeper marine layer tonight, with clouds likely
affecting most valley locations of L.A. and Vtu counties. Conds
will be mostly IFR tonight, except low MVFR in coastal areas s of
Pt. Conception. Gusty winds will affect the Antelope Valley this
afternoon and evening.

KLAX...Moderate confidence in the 12z TAF. There is a 20 to 30
percent chance that cigs will slip into the IFR category between
12z and 16z this morning. There is a 20 percent chance that cigs
will hold off until after 06z tonight.

KBUR...High confidence in the 12z TAF. There is a 10 to 20 percent
chance of MVFR vsbys between 13z and 17z this morning. There is a
20 percent chance that conds will remain VFR through 12z Fri morning.
&&

.MARINE...30/330 AM...

Good confidence that winds will drop below gale thresholds across
the northern two thirds of the outer waters by mid morning, but
then remain at SCA levels through late tonight. Good confidence in
SCA conds across the southern third of the outer waters through
late tonight. Steep combined seas of 8 to 11 feet across the outer
waters will slowly subside tonight.

For the Inner Waters, winds and seas are expected to remain below
SCA levels through the weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through Friday evening For
      zones 40-41-87. (See LAXCFWLOX).
PZ...Gale Warning in effect until 9 AM PDT this morning For zones
      670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Friday For zone
      676. (See LAXMWWLOX).

&&

$$

PUBLIC...RAT
AVIATION...DB
MARINE...DB
SYNOPSIS...RAT

weather.gov/losangeles



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