Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
210 PM PDT Sat may 30 2015
high pressure will bring above normal temperatures to
inland areas through Sunday. Temperatures will return to near or
just below normal next week as a weak frontal system approaches late
Sunday into Monday. A broad trough of low pressure will develop on
Monday and persist over the area through much of the coming
week...with a good chance of night through morning low clouds and
fog for coastal and valley areas.
Short term (today-tue)... temperatures up a few degree from
yesterday as the upper level ridge peaks. Temperatures across the
coastal areas on the other hand have not budged as a solid stratus
deck hugs all coastlines. This stratus is poised for an early return
this evening...and should push a little deeper inland over night
than last night...as the marine layer deepens a few hundred feet.
The ridge will shift to the east on Sunday...but should not be far
enough away to bring too much change tomorrow. Expecting very
similar conditions to today...except for a touch of cooling and
gustier onshore winds over the interior areas. A low pressure system
off the northern California coast will swing into Oregon Sunday
night into Monday. With the northeast track of this low...the
current frontal band should quickly dissipate as it moves down the
coast. Slo and sba counties may see some middle-level clouds...and all
areas will see a deeper marine layer with some spotty drizzle...but
otherwise no direct impacts are expected from the system. A healthy
dose of cooling is also on tap away from the stagnant coastal areas.
On Monday night and Tuesday...northwest flow will increase over the
region. This flow will likely result in gusty winds over the favored
I-5 corridor and Santa Ynez range areas. We should also see some
clouds banked up on the northern slopes as a result...and a decent
coastal eddy over Los Angeles and Ventura counties. This eddy will
likely bring clouds to most of the coastal and valley areas...as
well as the coastal slopes of the San Gabriel range. Southern sba
County should be mostly spared from the clouds thanks to the winds.
Temperatures will likely be similar to Monday.
Long term (wed-sat)... little change is expected on Wednesday when
compared to Tuesday...as mostly west-to-east zonal flow aloft
persists. Stratus should cover most coastal and valley areas...save
from the southern sba coast that will continue to see breezy
northwest winds. There is growing confidence for an upper level low
pressure system dipping into California on Thursday and Friday.
Computer projections however show a large range of solutions as to
where that system will settle and how strong it will be. The European model (ecmwf)
is the most aggressive...with the core of an unseasonable 567dm low
(at 500mb/20,000 feet above sea level) right over Southern
California on Friday. The GFS wobbles the much weaker 573dm low
about 100 miles off the coast. One detail that seems agreed upon
however is that the low should move very slowly...impacting the
region for a good 48-72 hour period. Did not add any mentionable
chances of rain at this point...but if the current projections hold
(especially the ecmwf)...showers will have a decent chance of
forming. Temperatures will also be below normal to no surprise. The
marine layer could weaken significantly depending on the strength of
the low. Being that this is rather uncommon for June...the computer
models may change its tune rather abruptly.
Middle/upper level trough of low pressure upstream will shift
northeast. Upper level moderate southwest winds and middle level light
south-southwest winds will prevail over the area. Marine inversion
base was approximately 1.3kft and cloud field was overcast this
morning. The base of the inversion will differ little and the cloud
field will be overcast Sunday morning. Weak to moderate onshore
pressure gradient will persist through the period.
Marine layer at lax at 1600z is 1350 feet deep and the inversion top
is at 2885 feet with a temperature of 21.6 degrees c.
Klax...there is a chance ceilings 007-010 through 30/20z then chance 008
between 31/02-31/05z. Chance ceilings 004 visibility 1sm br between 31/05-
31/12z then ceilings 006 visibility 3sm br between 31/12-31/17z and ceilings 010
visibility 5sm haze until 31/20z.
Kbur...chance visibility 4sm haze through 30/19z. Chance ceilings 003sm visibility 4sm
br by 31/11z.
Virtually certain - 95-100%
very likely - 80-95%
likely - 60-80%
chance - 30-60%
very unlikely - 20% or less
There is a chance Small Craft Advisory conditions will exist from
Piedras Blancas to San Nicolas Island including the west portion of
Santa Barbara Channel next week Tuesday through Wednesday with
northwest winds. Otherwise mixed swells originating from the
southern ocean and from tc Andres will persist but remain below
Small Craft Advisory for hazardous seas through Wednesday but
exposed areas will likely have extra surging and currents which may