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 230124
AFDLOX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
624 PM PDT Thu Jun 22 2017

.SYNOPSIS...

High pressure aloft centered over Southern Arizona will continue
warm conditions away from the coast into next week. Skies should
be fair, except for night through morning low clouds and fog
closest to the coast. A cooling trend should develop Tuesday as a
low pressure system off the California Coast will weaken the
upper-level dome of high pressure and increase onshore flow.

&&

.SHORT TERM...(THU-SUN)

Pretty big increase in low lvl southerly flow today resulted in a
significant cooling trend for coastal valleys south of Pt
Conception today. Farther interior areas above the marine lyr saw
little change other than an increase in winds. Not seeing a lot of
change in the pattern for tomorrow as gradient trends are
generally flat and there are minimal changes aloft. However, interior
areas north of Pt Conception should see a little cooling from
today as some of that cooler maritime air moves inland. Marine lyr
clouds will again struggle to clear the coast from about Malibu
north.

By late Friday into Saturday the low lvl flow is expected to
reverse as surface high pressure strengthens to the north. This is
expected to lead to a noticeable warming trend in most areas
Saturday along with some increase in north winds through the Santa
Ynez range and I5 corridor. These trends will continue into Sunday
which should be the warmest day of the period. Marine lyr is
expected to shrink in depth and areal coverage with clouds mostly
confined to the beaches north of Pt Conception and coastal LA
County. It`s possible the current heat advisory may need to be
expanded to cover some additional valley areas Saturday and/or
Sunday.

The NAM continues to show an increase in instability aloft
Saturday as some high level moisture and energy moves in from the
south. There are some decent lapse rates at very high levels but
the moisture is confined to 600mb and above. Not real confident in
this as the other models are much less unstable and don`t really
show much in the way of short wave features coming in from the
south. So for now will just indicate some high clouds moving in
Saturday but no thunderstorms. The main concern would be for dry
lightning given the lack of low lvl moisture but right now the
threat appears to be too minimal to include in the forecast.

.LONG TERM...(MON-THU)

Still very warm Monday but an increase in onshore flow should lead
to at least a few degrees of cooling for inland areas. Onshore
flow expected to increase a little each day through Thursday as a
series of troughs moves into the Pac NW. Confidence on the extent
of cooling beyond Tuesday is pretty low as models still show a lot
of differences with regard to how fast the high pressure ridge
will weaken and shift east. The GFS remains the coolest and
trending towards that solution for now.

&&

.AVIATION...23/0122Z.

At 00Z, the marine layer depth was around 1050 feet deep at KLAX.
The top of the inversion was around 3200 feet with a temperature
near 27 degrees Celsius.

IFR to MVFR conditions will spread into coastal terminals through
04Z then likely become primarily IFR through 08Z. There is a good
chance that LIFR conditions will develop through 10Z at coastal
terminals north of KOXR and continue through 14Z or 15Z. MVFR
conditions could linger at coastal terminals throughout Friday
afternoon.

KLAX...IFR to MVFR conditions will spread into KLAX through 03Z,
then become primarily IFR through 05Z. There is a 30 percent
chance that conditions could remain MVFR through 10Z, then
deteriorate to IFR in drizzle between 10Z and 16Z. After 20Z,
There is a 30 percent chance that MVFR conditions could linger
throughout Friday afternoon.

KBUR...VFR conditions are expected throughout the period, except
for a 40 percent chance of LIFR to IFR conditions as early as 07Z
or as late as 16Z.

&&

.MARINE...22/200 PM.

Winds will remain below Small Craft Advisory (SCA) level through
Friday then increase to above SCA levels in the outer waters Saturday
through Monday.

A 2-3 foot south swell will last through much of the week and
pose a risk for breaking waves nearshore. People boating or
kayaking near shore should use extra caution this week. A small
(2-3 feet) short period swell will impact the Santa Barbara
Channel and Santa Monica Basin over the weekend.

Although the coverage of dense fog is easing a bit, there is still
the possibility of patchy dense fog during the night and
mornings.

&&

.FIRE WEATHER...22/200 PM.

Hot and dry conditions will continue through Monday of next week.
The hot conditions will also bring the potential for plume
dominated fires which can create their own intense winds. Onshore
winds will peak today and Friday, which will focus the concerns to
interior Los Angeles County including the Angeles National
Forest, Highway 14 corridor, and the foothills of the Antelope
Valley. Weaker but locally breezy northwest winds should follow
Saturday through Monday...shifting the area of concern to Santa
Barbara County and the Tejon Pass.

Tropical moisture aloft will move through the area Friday night and
Saturday. While this should have little impact on humidities at the
surface, this has a 10 percent chance of producing high-based
thunderstorms. Confidence is incredibly low with this, but the
potential for dry lightning exists.

A Red Flag Warning is in effect through 9PM this evening for
the interior Los Angeles County Mountains and Foothills and will
not be extended. With rapidly drying fuels/vegetation however,
elevated fire weather concerns will persist through Monday,
primarily over all interior sections away from the influence of
the marine layer. If fire ignition occurs, dangerous fire behavior
should be expected. As such, the public should be extreme careful
when handling potential ignition sources such as cigarettes,
campfires, hand torches and metallic weed trimmers.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory in effect until 9 PM PDT Sunday for zones
      38-52-53. (See LAXNPWLOX).
     Beach Hazards Statement in effect through Saturday evening
      for zones 40-41-87. (See LAXCFWLOX).
     Excessive Heat Warning in effect until 9 PM PDT Sunday for
      zones 54-59. (See LAXNPWLOX).
     Red Flag Warning in effect until 9 PM PDT this evening for
      zone 254. (See LAXRFWLOX).
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK...(SUN-THU)
Hot temperatures with potential heat impacts will continue for
inland areas Sunday.

&&

$$

PUBLIC...MW
AVIATION...Hall
MARINE...Sweet
FIRE WEATHER...Kittell
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.