Area Forecast Discussion
Issued by NWS Los Angeles, CA

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390
FXUS66 KLOX 260531
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1031 PM PDT Sun Jun 25 2017

.SYNOPSIS...
High temperatures continue away from the coast today. Offshore
trends and a weakened marine layer will warm the coastal valleys
as well. A trough of low pressure off the California Coast will
weaken high pressure aloft beginning Monday afternoon and bring a
cooling trend as onshore flow strengthens.

&&

.SHORT TERM...(SUN-WED)

An upper-level ridge of high pressure over Southern Arizona will
flatten and recenter over Baja California early this week as a
trough of low pressure near 37n and 132w will move north of the
area. An increase in onshore flow will bring a cooling trend to
the area, more pronounced on Tuesday. A very warm and dry air mass
in place across the interior valleys and mountains of Los Angeles
County will combine with a stronger sea breeze circulation to
bring critical fire weather conditions to the area.

A northerly flow became a more pronounced today, which model
solutions failed to pick up on. Local temperature studies would
have been the way to go and would have provided a little better
results and reduced errors. MOS guidance values from last night
handled temperatures poorly missing by up to 15 degrees at KVNY
and up to 21 degrees at KBUR. Another warm day looks on tap for
tomorrow as the ridge remains in place ahead of the increasing
onshore push. Temperatures have been nudged higher in the latest
update bringing temperatures a few degrees cooler than today, yet
exceeding current guidance values for most valley areas. With a
delay in the sea breeze circulation, a heat advisory was extended
for the Los Angeles and Ventura County mountains into Monday
evening.

Locally gusty Sundowner Winds continue across the Santa Barbara
South Coast and Santa Ynez mountain range this evening as the a
marginal northerly gradient has developed across the area. No wind
advisory issuance is expected at this time as upper-level support
is lacking.

An update will be issued shortly.

*** FROM PREVIOUS DISCUSSION ***

By Tuesday or Wednesday, most areas should be back to normal high
temps. Marine lyr expected to expand to cover most coast and
valley areas by Wednesday.

Pretty strong northwest gradients expected across the Santa Ynez
range the next couple days but very minimal support aloft. So
while there will be gusty winds there they should generally remain
below advisory levels with the strongest winds up in the
foothills. Increasing westerly winds expected in the Antelope
Valley, especially Tuesday and Wednesday when they may be close to
advisory levels in the foothills.

.LONG TERM...(THU-SUN)

Nothing really remarkable in the weather from mid week on as we
maintain a fairly typical late June pattern. Weak troughing now
expected to remain in place going into next weekend with minimal
day to day changes in temps (near to slightly below normal) and
marine lyr coverage (coast/valleys night and morning).

&&

.AVIATION...26/0000z.

At 00Z...the marine layer depth was around 1100 feet at KLAX. The
top of the inversion was around 2250 feet with a temperature of
near 35 degrees Celsius.

Low-to-moderate confidence in the current forecast. There is a
chance of LIFR to IFR conditions at coastal terminals through 16Z.

KLAX...There is a 50 percent chance of IFR conditions at KLAX
between 10Z and 16Z.

KBUR...High confidence in VFR conditions throughout the period.

&&

.MARINE...25/1000 PM.

For the Outer Waters... Small Craft Advisory (SCA) level
conditions will continue through at least Tuesday evening. Wind
speeds may weaken to below SCA levels during the morning hours but
will strengthen again in the afternoon.

For the Inner Waters... SCA level winds will develop in the afternoon
and evening hours through Tuesday evening across the northern
nearshore waters as well as in the East Santa Barbara Channel.
Local gusts up to 25 kt could also develop during this time from
Point Mugu to San Mateo Point west of Santa Catalina Island.

In addition to the elevated winds, a short period west to
northwest swell could impact the coastal waters Monday through
Wednesday.

&&

.FIRE WEATHER...25/1000 AM.

Hot and dry conditions with gusty winds will continue through
Monday. Although a cooling trend will begin Monday...very dry
conditions are likely to persist into Tuesday. The hot and
unstable conditions will bring the potential for plume dominated
fires which can create their own intense winds. Gusty west to
northwest winds will impact interior portions of the forecast area
through Tuesday. For Los Angeles County, the strongest winds will
be in the I-5 corridor in the mountains as well as the Antelope
Valley foothills with gusts between 30 to 40 mph. Humidities in
the single digits to teens are expected across the mountains,
deserts, and interior valleys.

For Santa Barbara County, Sundowner winds will affect the western
portions of the Santa Ynez range and South Coast (mainly from
Gaviota to Goleta), with gusts of 30 to 40 mph each evening
through Tuesday. In addition, localized humidities falling to
between 15 and 25 percent can be expected in the Santa Ynez
mountains and adjacent canyons where the downslope Sundowner winds
develop.

The combination of hot and dry conditions with locally gusty winds
will bring elevated fire weather concerns to interior sections
through Tuesday, with brief critical conditions likely each
afternoon and evening in wind-prone areas...especially Monday
afternoon and evening. 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 Monday for zones
      53-54. (See LAXNPWLOX).
     Red Flag Warning in effect from 9 AM to 9 PM PDT Monday for
      zones 254-259-288. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday for
      zones 645-650-670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(WED-SUN)
No significant hazards expected.

&&

$$

PUBLIC...Hall/MW
AVIATION...Hall
MARINE...CK
FIRE...Gomberg/Smith
SYNOPSIS...jld

weather.gov/losangeles



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