Area Forecast Discussion
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FXUS66 KLOX 290305
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
805 PM PDT THU APR 28 2016
Mostly clear except a coastal low may bring an overnight
marine layer into early Saturday with patchy drizzle. A low will
approach from the East on Saturday with a slight chance of showers
and thunderstorms...with showers to linger in the deserts on
Sunday. A high will arrive by Monday with a warming trend...but
by midweek a low should approach with possible precipitation on
Upper level low pressure system currently centered over northern
Arizona will shift northeastward into Colorado by tomorrow
afternoon. Behind this system, there is still fairly strong
northwest flow aloft across Southwest California that will
continue to generate cool and breezy conditions for many
areas through Friday.
For tonight, the strongest winds will be focused across the
Santa Ynez mountains and Santa Barbara south coast, as well
as the I-5 corridor of the LA County mountains, where gusts
between 40 and 50 mph can be expected. The gale force northwest
winds near Point Concpetion will help to generate a Catalina
eddy circulation across the inner waters tonight into Friday
Already seeing pronounced south winds at Long Beach this evening
which seems to confirm that an eddy circulation will be underway
soon. Local WRF model shows a fairly strong eddy circulation
spinning up tonight with southeast-east winds of 10 to 15 knots
developing in the San Pedro Channel and Santa Monica Bay. This
eddy circulation should help to spin up considerable low clouds
across the LA coast/valleys tonight, potentially reaching the
Ventura coast on Friday morning. The marine layer is expected to
deepen to around 2000 feet by Friday morning across the LA Basin.
Should also see fairly extensive low clouds forming tonight north
of Point Conception along the Central Coast and Santa Ynez Valley.
Low clouds are expected to burn off inland on Friday afternoon,
but could see some low clouds linger near some of the coastal
*** From previous discussion ***
Another eddy will form Fri night with low clouds again expected
for the cst and some vlys of L.A./VTU County Fri night into Sat
morning. The marine layer should turn a bit deeper thanks to the
approaching upper level low, and patchy drizzle will not be out of
the question by Sat morning. Low clouds and fog should also
develop over the central Coast and santa Ynez Vly and Salinas Vly
Fri night into Sat morning. Otherwise, mostly clear skies can be
expected across the region Fri night into Sat, except for some mid
level cloudiness by Sat afternoon from the nearby upper low. There
will also be enough moisture and instability Sat afternoon for a
slight chance of thunderstorms for the L.A. County mtns and
Antelope Vly, with the potential of a thunderstorm drifting into
the Santa Clarita Valley and San Gabriel Vly, especially near the
Gusty w to n winds are expected again late Fri and Fri night for the
mtns, Antelope vly, and SBA County s cst, where advisory level wind
gusts will be possible in some areas. Gusty sub-advisory level nw
winds can also be expected along the Central Coast Fri afternoon and
It looks like another eddy will form over the SoCal bight Sat night
into Sun morning, with marine layer clouds and fog expected to
spread into the L.A./VTU County coast and some vlys Sat night and to
the SBA County S coast early Sun Morning. Offshore flow will develop
over SLO/SBA Counties Sat night into Sun morning to keep low clouds
away from the Central Coast. Otherwise, clear to partly cloudy skies
can be expected over the forecast area for the second half of
the weekend. Some moisture, cyclonic flow aloft, and increased
instability with strong May sunshine on Sun will result in a slight
chance of thunderstorms Sun afternoon and early evening over the
mtns of L.A./VTU/SBA Counties and across the Antelope Vly.
Temps over the area will continue to be a few degrees below normal
for many areas Fri thru Sun, altho should warm some to closer to
normal to slightly above normal for portions of SLO County, and in
the mtns and Antelope Vly, especially Fri and Sun.
The EC/GFS are in good agreement overall in the large scale features
Mon thru Thu. The upper trof will move e for Mon with a weak upper
ridge moving into srn CA for Mon and Mon night. A large upper level
trof is forecast to develop over the e Pac by Tue and slowly edge
its way toward SoCal thru Thu. Dry weather can be expected over the
region Mon thru Wed. Marine layer clouds should affect the coast and
some vlys Sun night into Mon morning, otherwise mostly clear skies
can be expected Mon thru Wed across the region. A low pressure
system associated with the deep upper trof will approach the
forecast area Wed night and thu, spreading some moisture into the
region by Thu. There should be increasing clouds Wed night followed
by a slight chance of showers developing on Thu. Since we are seven
days away from this event, there is only moderate confidence at best
that pcpn will develop on Thu. Further model runs should boost our
confidence in this late season weather event if models continue to
be consistent. There is even the potential for more significant pcpn
in showers and possible thunderstorms beyond the fcst period late
next week as the upper trof moves inland.
At 2300Z, Marine layer at LAX is 1400 feet with inversion
top temperature of 11.8 degrees celsius at 3700 feet.
Residual moisture and instability may generate isolated rain
showers through the early evening hours. Otherwise onshore
flow and low level moisture near the surface will likely
bring mvfr cigs into many coastal/valley areas tonight into
Friday morning. Eddy circulation expected to develop overnight
which should deepen the marine layer to around 2000 feet
by Friday morning across the LA Basin, resulting in low
clouds reaching the valleys. Gusty onshore winds each
afternoon and evening, with mdt uddfs and llws vcnty ksba
during evening hours.
KLAX...Mvfr cigs likely overnight but timing could differ
+/- 2 hours from TAF timing. Eddy circulation likely to
bring east-southeast surface winds late tonight into
Friday morning, but only a 20 percent chance that it could
reach 10 kt. A 20 percent chance of mvfr cigs lingering into
the afternoon hours on Friday.
KBUR...Mvfr cigs likely by around sunrise on Friday morning,
with a 20 percent chance of brief ifr conditions.
Northwest winds are beginning to subside over the outer
waters...but gale force gusts are likely to continue between San
Nicolas Island and Santa Rosa Island until the early morning
hours. Small Craft Advisory winds and seas are expected near-shore
in the Santa Barbara Channel and north of Point Sal.
Northwest winds will increase again Friday night and small craft
advisory conditions with gale gusts are likely again from Piedras
Blancas to Point Sal 10-60nm and from Point Sal to San Clemente
Island through Saturday morning. Seas over 10 feet and small craft
advisory for hazardous sea conditions from Piedras Blancas to San
Clemente Island through Saturday night as gales north of the area
persist. A south swell is expected to arrive Saturday and extra
currents and surging as well as hazardous surf are likely along
exposed south facing shores.
CA...Wind Advisory in effect until 9 PM PDT this evening For zones
34-35-59-87. (See LAXNPWLOX).
Beach Hazards Statement in effect until 9 PM PDT this evening
For zones 34-35-40-41-87. (See LAXCFWLOX).
Wind Advisory in effect until 3 AM PDT Friday For zones
39-52>54. (See LAXNPWLOX).
PZ...Gale Warning in effect until 9 PM PDT this evening For zones
645-670-673. (See LAXMWWLOX).
Small Craft Advisory in effect until 9 PM PDT this evening
For zones 650-655. (See LAXMWWLOX).
Gale Warning in effect until 3 AM PDT Friday For zone 676. (See LAXMWWLOX).