Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
820 PM PDT Friday Aug 22 2014
a trough of low pressure over the western United States will result
in night through morning low clouds and fog and slightly below
normal temperatures through the weekend. A warming trend is expected
after Monday of next week as high pressure develops.
Short term (tonight-mon)...
upper level trough will prevail across western states through
Monday...maintaining moderate to strong onshore flow through the period.
Marine layer depth expected to range between 1500 and 2000 feet through
the weekend...with night and morning low clouds and fog likely extending
into some of the valleys. Current satellite imagery already showing a much
quicker return of low clouds this evening across many coastal locations.
Temperatures will continue to run slightly below normal through the
weekend...with warmest valley locations expected to climb to around
90 degrees. Gusty onshore winds each afternoon and evening across the mountains
and deserts...with gusts as high as 45 miles per hour in the foothills of the Antelope
*** From previous discussion ***
The only sources of change will include the random ebbs and flows of
the marine layer and stratus coverage...as well as a little swath
of middle-level moisture streaming in on Sunday night and Monday which
could disrupt the marine layer over Los Angeles and Ventura
counties. At this point however...not expecting the cloud cover to
be enough to change it too much. No thunderstorm potential through
at least early next week.
Long term (tue-fri)...
a weak area of high pressure off Baja California and a high off the Oregon
coast will merge over California on Tuesday and Wednesday.
Meanwhile...onshore gradients will weaken and could even go a little
offshore in the morning hours. This all should spell a healthy
warming trend everywhere...with a gradually shrinking marine layer
influence. There is a chance that low clouds and fog go away
completely by Wednesday...but current forecast is on the
conservative side by having the clouds retreat to the coast.
Regardless...dense fog will be an increasing concern. No wind
concerns in the extended.
Still-brewing Hurricane Marie is slated to move parallel to the Baja California
coast through the middle-to-end of next week...staying about 800
miles offshore. By the time it is off the Southern California coast
on Thursday...we should see middle-level clouds move over the region.
This would bring a touch of cooling to the area Thursday and
Friday...but still above normal. While not expecting showers or
thunderstorms at this point...if the hurricane moves any closer to
shore it would move into the realm of possibilities. A large south
swell is also likely with the storms proximity.
Marine layer depth expected to range between 1500 and 2000 feet tonight
into Saturday...bringing IFR/MVFR ceilings to most coastal/valley taf
sites. Satellite imagery already showing an area of low clouds along
the immediate coastal areas of vtu and sba counties late this
afternoon...so expecting earlier arrival times tonight. Slower burnoff
expected across coastal areas expected on Saturday...with a chance of
ceilings lingering at klax...koxr...and ksba through the afternoon.
Klax...moderate confidence in 00z taf package. While klax will likely
see MVFR ceilings at some point tonight into Saturday morning...timing could
be +/- 2hours from 05z. There is a 20 percent chance of brief IFR conditions
tonight. There is a 30 percent chance of ceilings lingering through the
afternoon hours on Saturday.
Kbur...moderate confidence in 00z taf package. Leaning towards IFR ceilings
late tonight into early Saturday morning...but there is a 20 percent
chance that skies will remain clear.
Southerly swell 4 to 6 feet from Tropical Storm Lowell will
continue to impact the coastal waters through the weekend. Tropical
Storm Marie is expected to intensify rapidly into a major hurricane
in the eastern Pacific on Sunday and Monday. A long period southeast
swell (150 to 160 degrees) is expected to build across the Southern
California coastal waters on Tuesday and Tuesday night. The swell is
expected to peak on Wednesday into Thursday...with heights generally
ranging between 7 and 10 feet across the coastal waters. The swell
direction is gradually forecasted to shift to a southerly direction
during this time frame.
a high surf advisory is in effect through Sunday afternoon for
south facing beaches of Los Angeles and Ventura counties...with large
surf accompanied by dangerous rip currents. Earlier reports this afternoon
have generally shown peak surf heights in the 5 to 7 foot range across
south facing beaches...however Port Hueneme reported breakers up to
10 feet. This surf event originating from Tropical Storm Lowell is
expected to peak tonight through Sunday morning.
Confidence is growing that Tropical Storm Marie will intensify rapidly
into a major hurricane within the next 48 hours. Computer models have
been fairly consistent that the track and intensity of Marie will
bring the potential for a significant surf event for south and southeast
facing beaches. While it is still rather early...there is at least moderate
confidence that this could be the largest surf event seen in
recent years for a southerly event...with maximum sets of 10 to 13 feet
high surf advisory (see laxcfwlox).
High rip current risk (see laxsrflox).