Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 241631
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
931 AM PDT SUN JUL 24 2016

.SYNOPSIS...

High pressure across the southwest US 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-TUE)

No significant changes made to the forecast this morning. Just
about everywhere will be much cooler than yesterday, with 5-15
degrees of cooling expected in most places. However, even with the
cooling, most areas will remain slightly above normal. The
cooling will mostly be the result of an increase in onshore flow,
with only small decreases in height/thickness values. Low clouds
and patchy dense fog near the immediate coast this morning should
clear out by this afternoon, but wouldn`t be surprised if it hugs
the coast in a few places for much of the day. The main weather
concern for today will continue to be the extreme fire danger in
the LA County mountains, where a Red Flag Warning remains in place
through 10pm this evening for very low RH values and gusty south
to southwest winds. There should be much less in the way of smoke
across LA County and eastern Ventura County today, as south to
southwest winds aloft should transport smoke from the Sand Fire
northward.

***FROM PREVIOUS DISCUSSION***

There will be very little change to the weather on Monday. Hgts
are about the same as will be the SFC grads. The eddy is forecast
to spin up again so almost all of the beaches and near beach areas
will have some morning clouds.

All of the short range mdls show similar days Tue and Wed. The big
change will be with the daily stratus routine. It looks like the
eddy will pull a little more to the southwest which will drag the
clouds away from the VTA and SBA coasts. There will still be some
clouds over the LA coast as well as the Central Coast.
Synoptically an upper high forms over Nevada on Tuesday and then
moves over the CA/NV state line on Wednesday. There will really be
little day to day change in temps across the coasts and vlys...but
the mtns and interior sections will see some warming each day esp
Wednesday.

The highs westerly position will eliminate any chance of a
monsoon flow pattern.

.LONG TERM...(WED-SAT)

Both the EC and the GFS agree that the upper high will remain
nearly stationary over the NV/CA border on Thursday. The high hgts
will keep the marine layer stratus smooshed down on the beaches.
Warmer than normal temps will continue as well but the coasts and
vlys will be tempered some by the sea breeze. The interior not so
much and Thursday will be very hot with triple digit hear the
norm. The Antelope Vly will have highs mostly between 105 and 110
degrees. Still no monsoon flow.

Mdls disagree on the Fri/Sat day 6/7 forecast. The EC moves the upper
high westward right over the state which would result in very
little day to day change in the weather. The GFS moves the upper
high to the west. This solution would result in some cooling but
more importantly would open the door to the monsoon flow. Followed
the GFS for the extended forecast as its ensembles look a little
tighter than the EC`s. So there is a 20 percent chc of afternoon
and early evening convection over the la/vta mtns as well as the
Antelope Vly.

&&

.AVIATION...24/12Z...

At 08Z at KLAX, the inversion was surface based. The top of the
inversion was near 2800 feet with a temperature of 29 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. A
weak marine intrusion has been developing overnight in the
coastal areas south of Point Conception. Stratus that develops in
this area would likely result in LIFR/IFR conditions. Patchy dense
fog has been developing along the coast north of Point
Conception... affecting KSMX but not KSBP. Fog that develops in
this area would likely result in IFR/MVFR conditions. Low clouds
and fog will diminish by 18z. Smoke will be in the 120-150 height
range through much of Los Angeles and Ventura Counties. Otherwise
and elsewhere VFR conditions will prevail.

KLAX... Moderate confidence in the 12z TAF. The reduced
confidence is primarily due to the uncertainty in the timing and
intensity of the marine intrusion. A weak marine intrusion has
been developing overnight and should result in a short period of LIFR/IFR
conditions. Low CIGS will diminish by 17z. Smoke will be in the
120-150 height range through much of the forecast period.
Otherwise VFR conditions will prevail.

KBUR... Moderate to high confidence in the 12z TAF. The reduced
confidence is primarily due to the uncertainty in the timing and
intensity of the marine intrusion. There is a ten percent chance
of low CIGs through 15z. Smoke will be in the 120-150 height
range through much of the forecast period. Otherwise VFR
conditions will prevail.

&&

.MARINE...24/920 AM...

Not expecting any small craft advisories through at least
Wednesday. There will be some gusty NW winds across the NW portion
of the zone PZ670 through this afternoon. A strong eddy will
develop overnight into Monday morning across SoCal bight.
Sustained winds as high as 12 kt will be possible. Especially
across the San Pedro Channel both early Sunday and Monday morning.

There will patchy dense fog with visibility 1 nm or less through
mid afternoon off the central coast. The eddy should allow for
better visibility across the inner waters of Los Angeles, Ventura
and Santa Barbara counties through this afternoon.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning in effect until 10 PM PDT this evening For
      zone 254. (See LAXRFWLOX).
PZ...NONE.

&&

$$

PUBLIC...Sukup
AVIATION...KJ
MARINE...Kaplan
SYNOPSIS...Munroe

weather.gov/losangeles



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