Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 160327
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
827 PM PDT Mon Jul 15 2019

.SYNOPSIS...15/615 PM.

Gusty northwest winds will affect southern Santa Barbara County
and the Interstate 5 corridor tonight. Temperatures will gradually
cool Tuesday through Sunday. Overnight and morning low clouds
will be widespread in coastal and adjacent valleys by midweek.

&&

.SHORT TERM (MON-THU)...15/826 PM.

Latest GOES-West satellite imagery indicated a band of stratus
from the Palos Verdes Peninsula through the Santa Monica Bay and
moving across the coast into the southern portion of the Ventura
County Coast. Low clouds should remain no farther N than the
southern tip of the SBA South Coast later tonight due to the
northerly Sundowner winds. Although the marine layer was around
1200 ft deep this evening around LAX, low clouds should remain to
coastal areas due the northerly flow. The San Gabriel Valley could
see some patchy stratus well after midnight.

It was another warm to locally hot day across areas away from the
immediate coast of L.A. and Ventura Counties. A few cities reached
between 100-102 this afternoon including Woodland Hills, Chatsworth,
Saugus, Paso Robles, Acton and the Antelope Valley. Otherwise
most valleys were in the 90s including the Santa Monica Mountains
above the inversion. High temps across portions of the Central
Coast were 24 degrees warmer than yesterday. Port San Luis reached
91 degrees today compared to 67 degrees yesterday.

The shallow marine layer eventually scoured out across most
immediate coastal areas by early this afternoon, except lingered
across beaches in the Santa Monica Bay. No surprise with such a
strong inversion in place. The latest sounding at LAX around 630
pm showed a marine layer around 1200 ft deep. at 58 degrees F. At
the top of the inversion around 2200 ft., the temperature was
87.4 degrees F. That`s a strong inversion.

As mentioned in the earlier discussion, the primary weather this
evening is with the Sundowner Winds occurring mainly across the
western portion of the Santa Ynez Range and adjacent South Coast
of Santa Barbara County from Goleta to Gaviota and west. Pressure
gradients between SBA-SMX will continue to bump over the next few
hours expecting to peak around -4 mb later this evening. This will
continue to cause a good northerly gradient allowing for good subsidence
driving winds across the Santa Ynez Range to the coast. So far the
strongest winds were around Gaviota gusting around 45 mph. Winds should
strengthen further through this evening, peaking around 50 mph. Winds
will shift to the N to NE affecting portions of the Montecito Hills
later tonight, but winds are not expected to be as strong in this
area. Strongest winds expected to remain between Refugio and Gaviota
and adjacent foothills. The Wind advisory for the SBA South Coast
and adjacent mountains has been extended an additional 24-hours
from 4 AM Tuesday morning through 4 AM Wednesday morning. Wind
gusts around 35 mph should continue a few hours past sunrise
tomorrow, then decrease a bit for a few hours before increasing
once again late Tuesday morning through late Tuesday night. Winds
should not be quite as strong, but still warrant a wind advisory
with gusts 35 to 40 mph, mainly for the western portion of the SBA
South Coast,including Refugio and Gaviota areas.

...From Previous Discussion...

Gradients trend onshore Tuesday afternoon which should lead to a
couple degrees of cooling across interior areas. Northerly flow is
weaker as well so while gusty winds are expected again across the
Santa Ynez Range they won`t be as strong and temperatures won`t be
quite as warm as today`s event.

Stronger onshore trends expected Wed/Thu resulting in a deeper
marine layer and daytime temps dropping 4-8 degrees on average
from Tuesday`s levels.

.LONG TERM (FRI-MON)...15/144 PM.

Quiet weather pattern anticipated for the latter half of the week
into early next week. The cooling trend that will begin the middle
of this week will continue at a slower pace through Saturday as a
weak upper level trough sits along the west coast while the high
currently over the area shifts well to the east. Daytime highs
will be several degrees below normal with a deeper than usual
marine layer.

Those trends reverse Sunday as the trough weakens and high
pressure rebuilds from the east. Temps will bounce back to normal
by Monday and possibly back up to several degrees above normal by
the middle next week if current models solutions hold.

&&

.AVIATION...15/2349Z.

At 2310Z, the marine layer depth was 1100 feet. The top of the
inversion was 2200 feet with a temperature of 30 degrees Celsius.

N of Point Conception...Low confidence for coastal TAF sites with LIFR/IFR
conds. Mainly after 09z-10z. 40% chance no CIG but some MVFR
Vsbys issues overnight night into Tue morning. High confidence for
CAVU conds at KPRB.

S of Point Conception... Moderate confidence with continued
persistence forecast of IFR Cigs for Coastal TAFS in LA County.
There is a 30% chance for LIFR/IFR Cigs for OXR after 10z. 20%
chance for LIFR/IFR Cigs at KSBA after 12z.
KLAX...Moderate confidence in 06Z TAF. There is a 40% chance that
IFR conds will continue between 05-08z. After 08z, still moderate
confidence for LIFR/IFR Conds through 16z. Higher confidence for
VFR conds after 18z Tue.

KBUR...High confidence in 00Z TAF for CAVU conds through the
24-hour period.

&&

.MARINE...15/824 PM.

For the Outer Waters, moderate confidence in current forecast of
northwest Gales through tonight, with a Gale Warning in effect for
all the outer waters through 3 AM Tuesday. There is a 30 percent
chance of Gales again late Tuesday afternoon through Tuesday
night. SCA winds are likely if the gales do not materialize, and
should continue through Wednesday afternoon and possibly into
Wednesday evening.

For the Inner Waters north of Point Sal, moderate confidence in
current forecast. The SCA level winds have been extended through
late tonight, and there is a 60 percent chance of SCA level winds
Tuesday afternoon and evening. For Wednesday through Friday,
winds and seas are expected to remain below SCA levels.

For the Inner Waters south of Point Conception, moderate
confidence in current forecast. For the far western half of the
Santa Barbara Channel, there is a 50% chance of SCA level winds
tonight and a 40% chance of SCA level winds late Tuesday afternoon
and Tuesday night. Otherwise, winds and seas are expected to
remain below SCA levels through Friday.

&&

.FIRE WEATHER...15/235 PM.

Interior areas will continue to see elevated to brief critical
fire weather conditions through Tuesday due to gusty onshore
winds combined with very warm and dry conditions. Minimum
humidities will continue to be in the teens across interior areas
through Tuesday, except locally into single digits across the
Antelope Valley and Los Angeles county mountains. West to
northwest winds gusting between 25 and 35 mph will be common
through Tuesday morning across interior sections, shifting to the
southwest by Tuesday afternoon, with the strongest winds across
the Antelope Valley and Interstate 5 corridor. Triple digit heat
has occurred today across portions of the Los Angeles county
valleys, mountains, and Antelope Valley, with just a few degrees
of cooling on Tuesday.

An even more significant fire weather threat will occur across the
Santa Barbara south coast and Santa Ynez mountains through
tonight as gusty sundowner winds spread from west to east,
increasing late this afternoon into tonight. The current Santa
Barbara-Santa Maria pressure gradient is at -1.6 mb as of 2 pm,
projected to be around -4.5 mb by this evening. Already seeing
some northerly winds gusting between 20 and 30 mph in the hills
above Gaviota and Refugio early this afternoon, with temperatures
soaring into the lower to mid 90s. The strongest sundowner winds
will be focused across the western portions of the south coast
(from Gaviota to Goleta) and Santa Ynez mountains this evening,
where gusts between 40 and 50 mph are expected. Foothill and wind
prone coastal areas will see significant warming and drying
through this evening, with temperatures climbing into the 90s, and
humidities falling to between 12 and 25 percent. The gusty
sundowner winds combined with the very warm and dry conditions
will bring elevated to brief critical fire weather conditions
through tonight across the Santa Barbara south coast and Santa
Ynez mountains. A Red Flag Warning has not been issued yet for
this event as it does not appear that sufficient duration of Red
Flag conditions will occur, but this will be monitored closely
through the evening hours.

Stronger onshore flow combined with increasing marine layer depth
will bring a cooling trend Wednesday into the weekend. The
highway 14 corridor from Santa Clarita Valley to the Antelope
Valley will continue to have elevated fire weather conditions
through the week due to the strengthening onshore winds and
relatively dry conditions.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 4 AM PDT Wednesday for zones
      39-52. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zones 645-650. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Tuesday for zones
      670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (THU-MON).

No significant hazards expected.

&&

$$

PUBLIC...Kaplan/MW
AVIATION...Kaplan
MARINE...Smith
FIRE...Gomberg
SYNOPSIS...Kj

weather.gov/losangeles


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