Area Forecast Discussion
Issued by NWS Los Angeles, CA
FXUS66 KLOX 271153
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
453 AM PDT FRI MAY 27 2016
Weak low pressure will linger over the area through the weekend.
This system will keep afternoon temperatures a little below normal
through Sunday and generate a slight chance of mountain
thunderstorms Saturday afternoon. For next week, high pressure
will build in from the west. For inland areas, a gradual warming
trend is expected while a continued marine influence will keep
coastal temperatures nearly persistent.
Latest fog product imagery indicated a late surge of stratus
filling across the southern portion of the SoCal Bight and should
fill in across LA County Coast and coastal valleys and into
Ventura County coast and southern valleys by dawn. There was
plenty of stratus across much of the Central Coast and Santa Ynez
Valley as well. Latest AMDAR sounding showed the marine layer only
around 1600 ft this morning with a modestly stronger inversion in
place. This will help the low clouds become more organized through
this morning. Expect low clouds to scour out from the valleys
first, then to the coast by early afternoon.
Synoptically, a weak upper trough will sit over much of California
today through saturday. The weak upper low associated with the
trough will cutoff over southern california by Sunday morning.
This will keep high temps near or just below normal for this time
of year. The marine layer inversion should be a bit stronger and
more shallow than recent weeks, which should translate into a
more traditional night through morning low cloud regime, where
clouds will scour out from the valleys first, then to the coast by
late morning to early afternoon hours. Some immediate coastal
areas could see only partial afternoon clearing both Saturday and
Sunday afternoons. Some limited mid level moisture and instability
will likely generate some afternoon cloud buildups over the local
mountains this afternoon. On Saturday, there was a slight chance
of thunderstorms in the forecast for the Ventura/LA county mtns.
Although the instability looks decent, there will continue to be
limited mid level moisture and any storms that do develop will be
high based above 700 mb, so changed to slight chance of showers as
opposed to thunderstorms. it seems as though the NAM has been
overdone with convective parameters, as there has been no real
vertical cumulus cloud growth over the last few days, so not
terribly confident with showers developing. Models also show a
chance for afternoon showers over the same mountainous areas of
LA/VTU on Sunday but will hold off for now and let later shifts
look at it. The May Gray pattern will continue into next week.
Both the ECMWF and GFS are in pretty good agreement during the
extended period. The upper low will will shift east as an upper
ridge will build in from the eastern Pacific and persist through
at least next Wed before weakening as a broad upper level trof
over the e Pac approaches. The models start to diverge on
Wednesday as the ECMWF holds onto the upper ridging more so than
the GFS by Thu. Overall, it looks like a typical June gloom marine
layer pattern will prevail during the extended period with night
and morning low clouds and fog for the coast and coastal vlys.
The marine layer could be disturbed a bit across the central coast
Monday night/Tue Morning, and again the following night and
morning due to some weak offshore winds, but expect some patchy
low clouds to develop. Sundowner winds should also keep the SBA
south coast mostly clear with little chance of low clouds during
the same time period mentioned.
Temps are forecast to become increasingly warm and several degrees
above normal over interior areas, while the coast and adjacent vlys
will be near normal to a few degrees below normal thru the week. The
warmest day next week is expected to be on Wed with highs from the
upper 60s and 70s at the coast to upper 70s and 80s for the vlys and
foothills, except warming into the lower to mid 90s in the Antelope
At 11Z at KLAX...The marine layer was 2000 feet deep. The top of
inversion was 4500 ft with a temperature of 15 degrees Celsius.
N of Pt Conception, low clouds were widespread on the Central Coast
and in the Santa Ynez Valley, and were spilling into the Salinas
Valley. S of Pt Conception, clouds were beginning to push into
south coastal sections of L.A. County, and will become widespread
across coastal sections by daybreak. Clouds will likely push into
the San Gabriel Valley. Conditions were mostly low MVFR S of Pt
Conception, and IFR north. Expect skies to clear in most areas by
mid to late morning, except maybe early afternoon near the beaches.
More widespread low clouds are expected tonight/Sat morning, with
clouds expected in all coastal and most valley areas. Conds
should be mainly low MVFR or high IFR tonight.
KLAX...Moderate confidence in the 12z TAF. There is a 30 percent
chance that cigs will scatter out as early as 17z. There is
a 30 percent chance that cigs tonight will not arrive until
06z or later.
KBUR...Moderate confidence in the 12z TAF. There is a 30 percent
chance of MVFR cigs between 13z and 17z this morning. There is a
20 to 30 percent chance that cigs will arrive as early as 07z
tonight, and could be at IFR levels.
Across the outer waters, winds may drop below Small Craft
Advisory levels for a few hours this morning, but will likely
reach SCA levels again this afternoon through late tonight.
There is a 20 to 30 percent chance of SCA level winds
across the northern portions of the outer waters each
afternoon and evening Saturday through Monday.
Fairly high confidence that conds will remain below SCA levels
across the inner waters and the SBA Channel through Monday.
PZ...Small Craft Advisory in effect until 3 AM PDT Saturday For
zones 670-673-676. (See LAXMWWLOX).