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Area forecast discussion 
National Weather Service Los Angeles/Oxnard California
504 am PDT Monday Jul 25 2016

..aviation discussion updated...

Synopsis...

High pressure across the southwest U.S. And onshore flow will
support near to slightly above normal temperatures through most of
the next seven days with a return of night to morning low clouds
to coastal and valley areas. An influx of monsoonal moisture may
bring thunderstorms across interior areas late next week.

&&

Short term...(tdy-wed)

A 1200 foot marine layer is over the la basin. The marine layer
shrinks significantly north of la County where cigs and vis are
much Lower. Eddy did not develop as promised by the mdls so low
clouds are making their way inland in a more haphazard Manor
driven by a moderate onshore push both to the north and east. Sfc
grads are more onshore in both directions this morning compared to
last. There is some dense fog from Ventura up to slo County. The
increased onshore flow will likely keep a few beaches cloudy all
day long. Interior temps will not change much but the better
onshore push will continue the cooling trend for the coasts and
vlys.

There is some mid level moisture moving in from the south. Enough
to call it partly cloudy over la County. Right now it looks like
this moisture is at about 600 mb which is too high to produce a
worry of convection. Still mdls are not the best in handling this
kind of moisture advection and will have to keep an eye on it as
it moves into the area - if something does go wrong with the
forecast today it may well be a thunderstorm over the ern San Gabriel mtns
but still this is only a 10 percent chc which is too low for the
official forecast.

Both the ec and GFS agree that the Tuesday to Thursday period will
be rather static with an upper high anchored over Las Vegas. This
position of the upper high is not at all conducive to monsoon
flow. Temps will fluctuate some each day but will really not
change much through Thursday. The coasts will continue to have
night through morning low clouds and fog and there might be some
intrusion into the lower coastal vlys as well.

Long term...(thu-sun)

The long term is looking more and more like the short term. Now
both the GFS and ec are keeping the upper high in a more westward
location rather than moving it back east which was the forecast
earlier. If this more west solution comes to fruition there will
be no chc of afternoon convection. For now will keep the 20
percent chc of afternoon tstms in the forecast but if the 12z mdls
hold this pattern the tstms will have to be removed.

Otherwise slightly above normal temps will persist...esp inland.
The coastal night through morning cloud pattern will also
continue.

&&

Aviation...25/12z...

At 08z at klax... the inversion was 3200 feet deep. The top of
the inversion was near 4300 feet with a temperature of 27 degrees
celsius.

Overall... low to moderate confidence in the 12z tafs. The
reduced confidence is primarily due to the uncertainty in the
timing... location... and intensity of the marine intrusion. The
marine intrusion has been wafting in and out this morning at some
locations and is retreating from Los Angeles County in particular.
LIFR/IFR conditions at coastal locations this morning will diminish
in the 17z-19z time period. Smoke will be in the 110-150 height
range through much of Los Angeles and Ventura counties. Otherwise
and elsewhere VFR conditions will prevail.

Klax... low to moderate confidence in the 12z taf. The reduced
confidence is primarily due to the uncertainty in the timing and
intensity of the marine intrusion. The marine intrusion has been
wafting in and out this morning and is retreating in general from
klax. Any residual low clouds and fog will diminish in the 17z-19z
time period. Smoke will be in the 110-150 height range. Otherwise VFR
conditions will prevail.

Kbur... moderate confidence in the 12z taf. The reduced confidence
is primarily due to the uncertainty in the timing and intensity
of the marine intrusion. Ceilings at kbur are unlikely but smoke will
be in the 110-150 height range. VFR conditions will prevail.

&&

Marine...25/230 am...

Conditions will remain below Small Craft Advisory criteria
through at least midday Wednesday. Areas of dense fog with
visibility of 1 nm or less will be widespread across the coastal
waters today through mid morning.

&&

Fire weather... 24/200 PM...

Red flag warning will be allowed to expire at 2200 PDT today.
A moderate onshore pressure gradient will become weak later
this evening and any winds will diminish.

The relative humidity trended 10-15 percent higher
and temperatures 10-15 degrees cooler than Saturday at this time.
Temperatures Monday morning will differ little from this morning
and continue 5-10 degrees above normal. Temperatures will vary
plus or minus a couple of degrees each day and likely remain 5-10
degrees above normal through the week. Relative humidity will trend higher as
moisture pushes north through the period and overnight relative humidity will
range 25-35 percent in the warmer interior sections with mid teens
in the afternoon. Slight chance of thunderstorms are expected over
the Ventura and Los Angeles County mountains Friday through Sunday
with a lal of 2.

&&

Lox watches/warnings/advisories...
California...dense fog advisory in effect until 9 am PDT this morning for
zones 34-35-39. (See laxnpwlox).
Pz...marine weather statement in effect until 10 am PDT this morning.
(See laxmwslox).

&&
$$

Public...rorke
fire...30
aviation...kj
marine...kj
synopsis...Munroe

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