Area Forecast Discussion
Issued by NWS Los Angeles, CA
FXUS66 KLOX 282145
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
245 PM PDT THU APR 28 2016
Low pressure over the Great Basin will produce gusty winds for
some areas through late tonight. Another low pressure system will
move through Great Basin this weekend, bringing a chance for
isolated showers and thunderstorms. Warming is likely early next
week, followed by another chance for showers late next week.
Upper low centered over nrn AZ early this afternoon will drift
slowly e thru early evening. Altho there is lingering cold air aloft
and troffiness over swrn CA, the instability did not materialize to
any great extent this afternoon, with just stratocu development over
some of the mtns. Partly cloudy skies overall were noted across the
region this afternoon. High temps this afternoon will be similar to
yesterday and remain a few degrees below normal across the region.
Lingering gusty nw to n winds will also affect parts of the area
thru tonight, including the mtns of L.A./VTU/SBA Counties, Antelope
Vly, Central Cst, and SBA County s cst. Winds will be strongest this
afternoon and evening along the Central Coast and in the Antelope
Vly, with the strongest winds likely tonight elsewhere. Gusts of 40
to 50 mph can be expected, with the highest wind gusts in the mtns
and Antelope Vly. Wind advisories remain in place for these areas.
Please see the latest non-precipitation weather message (LAXNPWLOX)
for further details.
The upper low will continue to move e tonight and Fri, with weak
upper ridging moving toward the cst. Another upper level low is
forecast to move into NV Fri night and thru interior srn CA on Sat.
The upper low will drift e into AZ late sat night and Sun, with weak
upper troffiness lingering over srn ca thru Sun.
Skies will become mostly clear for much of the region tonight and
Fri, altho there should be some marine layer clouds over the
L.A./VTU County coast and some adjacent vlys later tonight into Fri
morning thanks to an eddy expected to develop over the socal bight.
Patchy low clouds and fog should affect the central Coast later
tonight into Fri morning as well. 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 foothills.
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.
Mid/upper level ridge of high pressure upstream will approach.
Upper level strong northwest winds and mid level moderate
northwest winds will prevail over the area. Isolated
thunderstorms between 28/23-29/03z with tops 25kft and moving
southeast at 30kt. Moderate onshore pressure gradient through
29/06z and after 29/21z otherwise weak northerly gradient. A weak
low level capping marine inversion is expected to develop tonight
with a base approximately 2kft and there is a chance a broken
cloud field will develop over the L.A. basin.
Marine layer at LAX at 1700Z is none.
KLAX...Chance cigs 012 between 29/11-29/20z.
KBUR...Chance cigs 013 after 29/13z.
virtually certain - 95-100%
very likely - 80-95%
likely - 60-80%
chance - 30-60%
very unlikely - 20% OR LESS
Northwest winds will continue to decrease today but gales will
likely persist from the Northern Channel Islands to San Clemente
Island and from Piedras Blancas to Point Sal 10-60nm through this
evening and small craft advisory conditions will exist elsewhere.
Northwest winds will increase again Friday night and small craft
advisory conditions with gale gusts will likely exist 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 will exist through Saturday night
as gales north of the area persist. A south swell will likely
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
645-670-673-676. (See LAXMWWLOX).
Small Craft Advisory in effect until 9 PM PDT this evening
For zones 650-655. (See LAXMWWLOX).