Area Forecast Discussion
Issued by NWS Los Angeles, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KLOX 251029
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
309 AM PDT MON JUL 25 2016

.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 TSTM 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...

25/06Z

At 05Z ay KLAX... the inversion was surface based. The top of the
inversion was near 4700 feet with a temperature of 26 degrees
Celsius.

OVERALL... Low to moderate confidence in the 06Z TAFs. The reduced
confidence is primarily due to the uncertainty in the timing...
location... and intensity of the marine intrusion. The marine
intrusion has already advanced to the coastline in most locations
from the Central Coast down through Los Angeles County. Whether
it remains solid or wafts in and out this morning is in question
as is whether it is able to get notably into the adjacent valleys.
LIFR/IFR conditions will prevail at coastal locations this morning
then diminish in the 17Z-19Z time period. LIFR/IFR conditions at
KBUR and KVNY will most likely occur 12Z- 15Z though there is a
thirty percent chance of the intrusion not getting strongly into
the SFV. Smoke will be in the 110-150 height rance through much of
Los Angeles and Ventura Counties. Otherwise and elsewhere VFR
conditions will prevail.

KLAX... Moderate confidence in the 06Z TAF. The reduced confidence
is primarily due to the uncertainty in the timing and intensity of
the marine intrusion. The marine intrusion has already moved into
the area but whether it remains solid or wafts in and out this
morning is in question. LIFR/IFR conditions will prevail this
morning then 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 06z TAF. The reduced confidence
primarily due to the uncertainty in the timing and intensity of
the marine intrusion. LIFR/IFR conditions at KBUR will most
likely occur 12z-15z though there is a thirty percent chance of
the intrusion not getting strongly into the area. Smoke will be
in the 110-150 height range. Otherwise 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. RH will trend higher as
moisture pushes north through the period and overnight RH 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...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...Rorke
FIRE...30
AVIATION...KJ
MARINE...KJ
SYNOPSIS...Hall

weather.gov/losangeles


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.