Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
1100 PM PDT Wednesday may 22 2013
New aviation discussion
Synopsis...
gusty northwest winds will continue into Thursday across the
mountains...deserts...and portions of the coast. An area of low
pressure will linger over the region through Tuesday and should
increase the night through morning low clouds and fog...with drizzle
early Thursday. Temperatures will stay below normal through next
Tuesday...then a warming trend should start to warm temperatures to
seasonal normals by midweek.
&&
Short term (tonight-sat)...a broad upper level low pressure system
across the West Coast will continue to influence our weather through
the short term. This has strengthened our onshore flow to the
desert...with lax-Daggett gradient peaking at +8 mb. Meanwhile the
northwest pressure gradient continues to tighten this evening across
the coastal waters...extending into portions of southwest California.
Gusty sundowner winds have materialized this evening across the sba
South Coast...with Gaviota reporting gusts up to 45 miles per hour and sba
Airport checking in with a gust of 32 miles per hour. Sba-smx gradient has
been trending offshore through the evening...with a current
reading of -4.6 mb. Wind advisories in effect tonight for the
sba South Coast and Santa Ynez range...with gusts up to 50 miles per hour
likely. While the stronger winds are currently focused from sba
westward to Gaviota...the gusty northerly winds are expected to
shift eastward overnight into Montecito hills. This is not a
particularly warm or dry sundowner wind event...but the strong winds
will still bring an elevated fire danger to the sba South Coast
tonight.
The wind advisories for the central coast will likely be allowed
to expire at 9 PM...as winds should begin to diminish there.
Meanwhile...wind advisories will also remain in effect until 3 am
for the I-5 corridor of the mountains and Antelope Valley...with
gusts up to 45 miles per hour for these areas.
The strong northwest flow around Point Conception will continue
to generate a well defined eddy circulation. This will maintain
a fairly extensive area of low clouds across Los Angeles County
and portions of Ventura County...with a marine layer depth
expected to be around 3000 feet. The deepening marine layer
could generate patchy drizzle across the la basin overnight
into Thursday morning...especially the foothills of the San Gabriel
Mountains.
*** From previous discussion ***
Northwest flow expected to slacken Friday into Saturday, allowing
the marine layer clouds to start migrating north up the coast. Not 100
percent confident they will fill in along the central coast but will
stick with that for now. Daytime highs expected to dip a few more
degrees Thursday with the trough and marine layer deepening. Still
relatively warm across the sba County South Coast due to subsidence
from the north winds over the Santa Ynez range.
Trough lifts a tad Friday and the eddy expected to weaken as well so
most areas should be a couple degrees warmer. Again the opposite
trend for sba with northerly winds weakening. Then turning cooler
with a deeper marine layer Saturday as the trough again deepens along
the West Coast.
Long term (sun-wed)...models differing with the details on next
week but impacts pretty minimal either way. Main thing to watch for
is the possibility for northwest winds increasing again across the
western and northern portion of the forecast area, possibly leading
to more gale force winds over the outer coastal waters and gusty
sundowners and i5 corridor winds. Temperature trends also unclear as
the GFS is tending to shift towards weak ridging by Tuesday while
the European model (ecmwf) shows another trough coming in Tuesday and Wednesday.
&&
Aviation...
23/0600z
3500 foot marine layer will bring MVFR to low VFR ceilings from klgb to
klax. Only fair confidence in clearing times as eddy could keep
broken-overcast conds in later the forecast.
Klax...fair confidence in taf. A 30 percent chance of ceilings lasting
until 22z. Good confidence that east wind component will remain under
8 knots.
Kbur...fair confidence in taf. A 30 percent chance ceilings could last
until 19z. A 40 percent chance that ceilings could rise to 035.
&&
Lox watches/warnings/advisories...
Wind Advisory (see laxnpwlox).
Gale Warning (see laxmwwlox).
Small Craft Advisory (see laxmwwlox).
High surf advisory (see laxcfwlox).
High rip current risk (see laxsrflox).
&&
$$
Public...gomberg/mw
aviation...asr
synopsis...seto
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