Scientific Forecaster Discussion
Southwest California area forecast discussion...updated
National Weather Service Los Angeles/Oxnard California
355 am PDT Friday may 29 2015
Updated aviation and marine sections
A relatively quiet pattern expected over the next week. High
pressure aloft will allow for very warm inland conditions...while
coastal areas will remain mild due to the marine layer influence
through Sunday. A cooling trend is expected next week as an upper
trough persists over the region. Night through morning low clouds
are likely to reach coastal valleys.
Short term (today-sun)...latest fog product indicated low clouds
across the central coast and Santa Ynez Valley. Marine layer stratus
was starting to fill in across the Los Angeles County coast and into
the southeast portion of the San Gabriel valley. By sunrise...most coastal
areas S of Point Conception should fill in due to a weak eddy across
the socal bight. Latest amdar sounding near lax indicated an
inversion around 1000 feet deep which is much more shallow than the
previous nights. This was expected as an upper ridge axis has built
in over the entire West Coast. This upper ridge axis will linger
through Saturday before it breaks down and pushes east as another
upper trough in the eastern Pacific moves into California as early
as Sunday and persists through most of next week.
With the marine layer much shallower than in weeks past...low
clouds will likely scour out to the beaches a bit faster...with a
few immediate coastal areas having a tough time clearing out. This
same stratus pattern can be expected through Sunday morning...with
most valley locations S of Point Conception remaining mostly
clear...with the exception of the southeastern portion of the
San Gabriel valley.
As far as high temperatures for today and Saturday...coastal areas will
remain under a marine layer influence with high temperatures remaining in
the upper 60s to lower 70s along the coast...warming up to the upper
70s to lower 80s inland. Valleys will continue to be quite warm with
warmest valley locations reaching the middle 80s to around 90
today...with a few more degrees of warming on Saturday which should
be the warmest day over the next week. By Sunday...the ridge axis
will have been replaced with a broad upper trough associated with a
cutoff low just of the northern California coast. The marine layer
is expected to deepen in advance of the trough...which will help to
cool most areas a few degrees north of Point Conception...while the
valleys of la/vtu counties will be similar or a degree or two
Long term (mon-thu)...both the GFS and European model (ecmwf) are indicating a
persistent upper trough pattern across California through most of
the week. Expect modest widespread cooling through Wednesday...with
more significant cooling on Thursday. The marine layer will deepen
up allowing for stratus to reach the coastal valleys most night
through mornings. Not expecting any precipitation...but there could
be some early morning patchy local drizzle over la/vtu County coast
and valleys...with cooler than normal high temperatures.
At 0844z the marine layer depth at klax was around 1500 feet
deep. The top of the inversion was around 4400 feet with a
temperature of 20 degrees celsius.
Widespread IFR conds in all coastal areas this morning...except
locally low MVFR across l.A. County coastal sections. IFR ceilings have
overspread the San Gabriel valley...and were widespread in the
Santa Ynez and Salinas valleys. Expect IFR conds to push into the
remainder of the l.A. And vtu County valleys...with the exception of the
Santa Clarita valley. Expect skies to clear by middle to late morning
in most areas...although ceilings could linger into the afternoon near
the coast. Similar low cloud pattern expected tonight/Sat
morning...possibly slightly less widespread in the valleys.
Klax...low to moderate confidence in the 12z taf. There is
a 20 to 30 percent chance that ceilings will slip into the IFR
category between 12z and 15z. There is a 20 to 30 percent
chance that ceilings will linger through at least 22z.
Kbur...moderate confidence in the 12z taf. There is a 10 to 20
percent that skies will remain VFR this morning. There is a 20
percent chance skies will scatter out as early as 15z.
Fairly high confidence that Small Craft Advisory conds across the outer waters will
decrease below Small Craft Advisory levels by middle morning. Winds should remain
below Small Craft Advisory levels...except for some occasional gusts during the
afternoon and evening hours...through Sunday.
Across the inner waters...fairly high confidence winds will remain
below Small Craft Advisory levels through Monday.
Small Craft Advisory (see laxmwwlox).