Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
440 am PDT Tuesday may 21 2013
..aviation discussion updated...
Synopsis...
a cooling trend will begin today and continue through
Thursday...along with an increase in night through morning low
clouds and fog. Cool weather with plenty of night through morning
low clouds and fog will likely continue through the Holiday
weekend.
&&
Short term (today-thu)...
eddy circulation has developed across the inner coastal waters this
morning. Amdar soundings out of klax have showed a steady deepening
of the marine layer last evening through early this morning...with
its depth now up to about 1800 feet. Low clouds have already
overspread coastal areas of l.A. And vtu counties...and the valleys
of l.A. County with the exception of the Santa Clarita valley. By
daybreak...expect clouds to push into the vtu County valleys and
into coastal sections of southern Santa Barbara County. North of pt
Conception...stratus was more patchy in nature...possibly disrupted
by a thick band of high cloudiness pushing into the coast. Expect
the low clouds to clear in most areas by late morning...but with
increasingly strong onshore gradients...there is a chance that some
clouds could linger near the beaches...especially across vtu and
l.A.Counties. There will be enough high cloudiness to use partly
cloudy wording across the region aside from any low cloud issues.
Maximum temperatures will be down significantly today...especially in the
valleys...where highs will likely be 8 to 12 degrees lower than they
were yesterday in most areas. The increase in onshore flow will
bring gusty winds to the mountains...the Antelope Valley...the Santa
Clarita valley and the central coast this afternoon. At this
time...expect winds to remain just below advisory levels...with
gusts of 30 to 35 miles per hour expected...except possibly to 40 to 45 miles per hour
across western portions of the Antelope Valley.
An upper low will move into the Pacific northwest tonight and Wednesday...with a
sharpening trough extending southward through California. North-S gradients will
increase across the region tonight...and gusty northwest to north winds will
likely affect locations through and below passes and canyons of the
Santa Ynez range in southern sba County. Expect winds to remain just
below advisory level in these areas as well.
Expect low clouds across most coastal and valley areas tonight and
Wednesday morning. However...across the sba County S coast...northerly winds
will likely allow skies to remain clear there. Expect clouds to
clear fairly well on Wednesday...although they may linger into the
afternoon once again near some beaches of l.A. And vtu counties.
Gusty west to northwest winds will affect the Interstate 5 corridor
tonight and Wednesday...likely staying below advisory levels. Maximum temperatures
will be down a few more degrees in most areas Wednesday.
The upper low will continue to spin across the Pacific northwest Wednesday night and
Thursday...but the trough across California will sharpen up a bit. The marine
layer should deepen a bit more...and night/morning low clouds and
fog may have to be added to the Santa Clarita valley and possibly
even the coastal slopes. Increasingly cyclonic height pattern aloft
suggests that there may be enough lift to produce some drizzle
late Wednesday night/Thu...mainly in coastal sections of l.A. And vtu
counties. North-S grads will continue to increase...and advisory level winds
are possible across the sba County S coast and across the Interstate
5 corridor Wednesday night. On the central coast...winds will approach
winds advisory levels during the afternoon hours of both Wednesday and
Thursday. Thursday looks to be the day with the greatest potential for clouds
lingering at the beaches of l.A. And vtu counties. Temperatures will be
down a couple of more degrees in most areas on Thursday...down to several
degrees below normal in most areas.
Long term (fri-mon)...a large upper low will continue to spin
across the Pacific northwest through the Holiday weekend...with
troffing extending southward into the forecast areas. For Friday
through Monday..expect plenty of night through morning low clouds and fog
in coastal and valley areas. Temperatures will likely be at least a few
degrees normal through the period.
&&
Aviation...21/12z.
Coastal low clouds and fog will thin after daybreak but some
locations will not clear prior to the marine layer returning after
00z. Forty percent chance of gusty northerly winds across the Santa
Barbara coastal mountains and South Coast 00z-08z. VFR elsewhere.
Klax...IFR conditions will continue through 18z-20z then the cloud
deck will thin during the day. IFR conditions return 02z-06z
with a 40 percent chance of LIFR.
Kbur...IFR conditions will continue through 17z-19z then the cloud
deck will thin during the day. IFR conditions return 06z-10z with
a 20 percent chance of LIFR.
&&
$$
Public...db
aviation...kj
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