Scientific Forecaster Discussion
fxus66 klox 171017
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
317 am PDT Wed Jul 17 2019
Area temperatures will gradually cool through the week and will
be below normal in many locations by Friday. They warm again over
the weekend and into next week. Overnight and morning low clouds
and patchy fog will continue to keep coastal areas cooler and
adjacent valleys at times as well.
Short term (tdy-fri)...17/316 am.
A stronger than normal eddy has spun up. It has generate a 10kt
east wind at klax. It has also lifted the marine layer from 1000
feet ydy evening to a 1700 foot value now. This strong eddy will
likely bring low clouds to all of the csts and vlys south of pt
Conception (except for the Santa clarita) by dawn. Things are
happening a little slower north of pt Conception but there is a
grip of stratus advecting over the waters in from the north and
this will likely bring at least areas of low clouds to the central
coast by daybreak. The eddy and the low clouds will bring plenty
of cooling to the coasts and esp the vlys today. Slightly lower
hgts will cool the interior slightly except for Paso Robles which
will cool dramatically with all day south winds forecast.
The onshore flow increase a little each day Thu and Fri. The eddy
is forecast to continue. There will low clouds covering all of the
coasts and vlys (probably not but possibly the Santa Clarita Vly
as well) some beaches will likely remain cloudy all day Thursday
and there is a possibility that many beaches will not clear on
Friday. Max temps will drop each day and Max temps will be below
normal both days. Most Vly temps will be over 10 degrees blo
Long term (sat-tue)...17/316 am.
Not much change on Saturday- there are offshore trends so there
such be better and faster low cloud clearing. The ec pushes 500 mb
hgts up a little which would warm the interior some but the GFS
has no change.
On Sunday a large upper high that was sitting over the Texas
Panhandle will move westward and take up residence over The Four
Corners areas. It will persist there for the remainder of the
period and likely remain week. Hgts rise to about 593 dm and the
onshore flow relaxes. The marine layer will be smooshed out of the
vlys. Clearing should be complete each afternoon due to the weaker
than normal onshore flow but there is a chance that the marine
layer will be so squished and topped by a massive inversion that
it will have a hard time clearing the beaches. MOS is downplaying
the Max temps with only near normal Max temps forecast but with
these hgts and grads it is hard to imagine Max temps coming in
several degrees warmer than MOS fcst.
Right now mdls hold off on any monsoon moisture transport until
day 8 (wednesday) still any time there is Four Corners high there
is some risk of some moisture sneaking in.
At 0550z at klax, the marine layer depth was 1000 feet. The top
of the inversion was near 2900 feet with a temperature of 24 c.
High confidence in kprb, kpmd and kwjf tafs.
Low confidence in ksba taf where there is a 40 percent chc of IFR
Low confidence in ksbp taf where there is a 40 percent chc of no
Moderate confidence in remaining tafs. Arrival timing may be off
by 2 hours. VFR transition should occur within an hour of fcst.
There is a 30 percent chc of MVFR cigs after 11z.
Klax...moderate confidence in taf. Low clouds could arrive as
early as 07z. There is a 30 percent chc of MVFR cigs after 11z.
VFR transition is likely between 19z and 21z. There is a 30
percent chc of an 8kt east wind component 11z-16z.
Kbur...moderate confidence in taf. Low clouds could arrive as
early as 09z. There is a 30 percent chc of MVFR cigs after 11z.
VFR transition is likely between 17z and 1830z.
For the outer waters... Small Craft Advisory (sca) level winds
will continue through midday then gradually diminish. The winds
will become elevated again Friday through Sunday but will likely
remain below advisory level.
For the inner waters north of Point Sal... conditions will remain
below advisory levels through Sunday.
For the inner waters south of Point Conception... conditions will
remain below advisory levels through Sunday.
California...Wind Advisory in effect until 4 am PDT early this morning for
zones 39-52. (See laxnpwlox).
Pz...Small Craft Advisory in effect until 3 PM PDT this afternoon
for zones 670-673-676. (See laxmwwlox).
Hazard potential outlook (fri-tue).
No significant hazards expected.