Area Forecast Discussion
Issued by NWS Los Angeles, CA
FXUS66 KLOX 270316
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
816 PM PDT THU MAY 26 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.
Satellite imagery showing mostly clear skies across the district this
evening, except some low clouds beginning to return to portions of
the Central Coast. Gusty west-northwest winds remain across the
mountains and deserts, as well as the SBA south coast this
evening. Winds across the SBA south coast and Santa Ynez mountains
will locally approach wind advisory levels this evening, as
current SBA-Santa Maria gradient at -3.9 mb.
ACARS sounding showing marine layer depth at LAX around 2000 feet
this evening, with a more established marine inversion. This in
combination with a developing eddy circulation is expected to
bring a more established marine layer low cloud pattern to the
coastal/valley areas tonight into Friday morning. Little change
in temperatures expected across the coast on Friday, but slight
warming for interior sections.
Some mid level moisture and instability will likely generate some
afternoon cloud buildups over the local mountains on Friday
afternoon. Not totally out of the question that a few showers
could develop over the Ventura county mountains tomorrow
afternoon, but not even a 20 percent probability to highlight
at this point.
*** From previous discussion ***
A broad mainly nw flow aloft will prevail over swrn CA thru Fri as
upper level ridging lingers off the coast. A weak, baggy upper level
trof will develop over srn CA Fri night and Sat. The upper trof will
become a weak upper level low over swrn CA Sat night then drift off
to the se on Sun.
The marine inversion will further strengthen over the next couple of
days. This will help more organized and extensive night and morning
low clouds and fog to develop for the coast and adjacent vlys
tonight thru Sat morning, with an eddy helping to enhance the marine
layer clouds s of Pt Conception. However, some offshore flow over
interior areas to the Central Coast later Fri night into Sat morning
may diminish low cloud coverage for the Central Coast and Santa Ynez
Vly by early Sat morning. There will be the possibility of afternoon
cu buildups in the mtns Fri and Sat, altho the 12Z NAM was
indicating there should be enough instability for the formation of
isolated showers or thunderstorms Sat afternoon in the VTU/interior
SBA County mtns. LI`s down to -6, CAPE values over 1200 J/Kg, and
the presence of the weak upper troffiness would support this
possibility as well. Have decided to include a slight chance of
thunderstorms for these areas, and also into the L.A. County
mtns along the I-5 corridor, for Sat afternoon into the evening.
Otherwise, mostly clear skies are expected over the forecast area
tonight thru Sat. Good onshore flow in the afternoon and evening
hours will prevail on Fri, with gusty sw to nw winds from the
Central Coast to the foothills, mtns and deserts, then weaker
onshore winds are expected for Sat. Gusty nw to n canyon winds are
also expected along the SBA s coast and mtns this evening, which may
approach advisory levels at times.
The marine layer pattern will continue Sat night and Sun, with low
clouds and fog into the cst/vlys. Lingering instability and some
moisture should result in afternoon cu buildups in the mtns sun
afternoon and early evening. In addition, there is slim, non-zero
chance of a shower or thunderstorm over the San Gabriel Mtns Sun
afternoon as the upper low slides off to the se, but POPS in this
area will be below 15 percent so there is no mention in the zones.
Otherwise, mostly clear skies will likely continue across the
Temps are forecast to turn slightly warmer for Fri thru Sun,
especially over interior areas. Even so, highs will be generally 3
to 6 deg below normal for the cst and adjacent vlys, while inland
vlys, mtns and deserts will be near normal to slightly above
EC and GFS are in generally good agreement during the extended
period. The upr trof will continue to move slowly e Sun night and
Mon while upper level ridging starts to build in. The upper ridge
will move over the area Tue thru Wed before weakening as a broad
upper level trof over the e Pac approaches. The EC, however, 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 period with night and morning low clouds and fog for the
coast and adjacent vlys, altho slight offshore flow over SLO/SBA
Counties during the night and morning hours Wed and Thu may help to
minimize low clouds there. A lowering and strengthening marine
inversion should also cause the low clouds to be just patchy overall
for the vlys of VTU/L.A. Counties from Tue night into Thu morning.
Otherwise, mostly clear skies can be expected Mon thru Thu.
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 0000Z at KLAX...The marine layer was 3000 feet deep with the
top of inversion at 4500 ft and 13 degrees celsius.
There is moderate confidence with the 00z tafs in respect to
better organized marine layer stratus expected over the next
12-18 hours, with cigs mostly in mvfr category. Potential llws
concerns at KSBA this evening due to gusty NW winds near adjacent
passes and canyons.
KLAX and KBUR...There is moderate confidence in the 00z TAF.
There is a 30 percent chance of clear to sct conditions through
Small Craft Advisories will continue across the outer waters
through Friday morning, with some zones possibly needing to be
extended into tomorrow evening. An eddy circulation is expected to
generate some light south-southeast winds across the inner waters
on Friday morning. Models were hinting at a larger southerly long
period swell moving into the region in the middle of next week.
PZ...Small Craft Advisory in effect until 9 AM PDT Friday For
zones 670-673-676. (See LAXMWWLOX).