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Area Forecast Discussion (AFD)

Issued by Los Angeles, CA (LOX)

                            
000
FXUS66 KLOX 260230
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA 
730 PM PDT Sun Aug 25 2019

.SYNOPSIS...25/714 PM.

Above normal temperatures will continue through much of the week 
with increased humidity through Monday. Overnight and morning low
clouds will remain along the coast through Tuesday then may push
into some adjacent valley areas later in the week.

&&

.SHORT TERM (SUN-WED)...25/729 PM.

***UPDATE***

594 hgts, a minimal marine layer and weak onshore flow all added
up to an increase in temps today. Most beach areas warmed 1 to 2
degrees while most of the interior saw 2 to 4 degrees of warming.
The northern portion of the VTA mtns, however, saw 6 to 12 degrees
of warming. Almost all areas had above normal temps today. A
shallow 800 foot marine layer will bring low clouds to the VTA
west coast and to the Central Coast. Although not in the forecast
it is possible that the LA beaches and the SBA south coast will
see some clouds as well. There is not that much onshore flow so
even if there are marine layer clouds there will not be that much
inland penetration.

Tropical Depression Ivo is mostly gone but it has released a grip
of mid level clouds and skies will slowly turn mostly cloudy
overnight tonight and will then clear to partly cloudy tomorrow.

Slightly stronger onshore flow and slightly lower hgts as well as
some cloud cover will bring a couple degrees of cooling.

***From Previous Discussion***

For tonight and Mon, the forecast area will be under the southern
portion of an elongated upper level ridge extending from off the 
nrn CA coast thru central and sern CA into AZ. However, the 
remnant upper level low from Tropical Depression Ivo will move up 
from the S and just off the srn CA coast thru Mon night and off 
the central CA coast on Tue. This is expected to slightly weaken 
the upper level ridging over the forecast area on Mon with the 
ridging pushing to the N and E into Tue. Even so, H5 heights will 
remain rather high over swrn CA and be in the 593-594 DM range 
thru this evening, and in the 590-592 DM range for the most part 
later tonight thru Tue. The upper level flow will be from the E 
and SE thru Mon then turn more to the S Mon night into Tue. Upper 
level ridging is then expected to build back into srn CA Tue night
and Wed with H5 heights increasing to 592-593 DM and the upper 
level flow turning SW.

The marine inversion will likely remain surface-based at VBG and 
be around 600-800 ft deep at LAX tonight thru Mon, then deepen 
perhaps a couple of hundred feet or so Mon night into Tue morning 
and again Tue night into Wed morning. Low clouds and fog should 
affect mainly the Central Coast along with the VTU/L.A. County 
coast each night and morning thru Tue, then expand to the SBA 
County S coast and some of the adjacent vlys Tue night into Wed 
morning. Patchy dense fog will be possible with any low clouds 
along the Central Coast thru Tue morning as well. Otherwise, 
generally fair skies will prevail tonight and Mon, with varying 
amounts of mid and high level clouds from the remnants of Ivo 
expected to move into the area from the S, then mostly clear skies
can be expected Mon night thru Wed.

Afternoon onshore gradients (LAX-DAG) are forecast by the NAM to 
be around +7.3 mb Mon, +8.0 mb Tue and +7.6 mb Wed. These 
gradients will continue to promote some gusty S to W winds each 
afternoon and early evening across the foothills, mtns and 
deserts. In addition, NAM forecast gradients from SBA-SMX will 
lower to -2.1 mb this evening and -1.4 mb Mon evening, with 
locally gusty sundowner winds possible each evening along the SBA 
S coast and Santa Ynez mtns, especially W of Goleta.

With decent warming in the boundary layer and at 950 mb, and high
1000-500 mb thicknesses (582-586 DM), temps away from the coast 
are forecast to warm further Mon and Tue to about 5-12 deg above 
normal. Temps should then cool slightly but remain several degrees
above normal for inland areas Wed. Highs for the warmest vlys and
lower mtns will be in the mid 90s to about 104 Mon and Tue, and 
in the 90s to near 100 on Wed.

.LONG TERM (THU-SUN)...25/240 PM.

The upper level ridging will build back into srn CA Thu thru Fri 
while strengthening into a 593-595 DM upper level high. The upper 
level high should persist into Sat, then build back toward the 
Four-Corners region for Sun with H5 heights over swrn CA lowering 
slightly to 591-592 DM. 

The marine inversion could be possibly up to 1000 ft deep Wed 
night into Thu, then shrink to 500-800 ft deep or so Fri thru Sun.
Night and morning low clouds and fog are expected along the 
Central Coast thru the period, and the VTU/L.A. County coast into 
Thu morning, and just the L.A. County coast Fri thru Sun. 
Otherwise, mostly clear skies ca be expected across the forecast 
area thru the extended period.

Temps will continue to be several degrees above normal away from 
the coast Thu thru Sun. Highs in the warmest vlys and lower mtns 
should be generally in the 90s to near 100 each day, with the 
Antelope Valley ranging from the upper 90s to around 102.

&&

.AVIATION...26/0007Z.

At 2335Z at KLAX, the marine layer was 800 ft deep. The top of 
the inversion was 1800 feet with a temperature of 26 C.

High confidence in inland TAFs.

Low confidence in coastal TAFs with a 40 percent chc of LIFR/IFR
cigs at sites with no cigs fcst and a 30 percent chc of no cigs at
sites with low clouds forecast. Cig arrival time could be off by 2
hours.

KLAX...Low confidence in TAF. There is a 40 percent of BKN004
11Z-15Z. High confidence in no east wind component.

KBUR...High confidence in CAVU TAF.

&&

.MARINE...25/133 PM.

For the Outer Waters, moderate to high confidence in the 
forecast. High confidence in winds and seas remaining below Small 
Craft Advisory (SCA) levels thru Wed. On Thu, there is a 60% 
chance of SCA level winds during the afternoon and evening hours.

For the Inner Waters north of Pt. Sal, moderate to high 
confidence in the forecast. High confidence in winds and seas 
remaining below SCA levels thru Wed. On Thu, there is a 30% chance
of SCA level winds during the afternoon and evening hours.

For the Inner Waters south of Pt. Conception, moderate to high 
confidence in the forecast. Conditions are generally expected to 
remain below SCA levels thru Thu. 

Patchy dense fog with visibility of one nautical mile or less is
across the coastal waters this morning and again during the late
night thru morning hours Mon and Tue. 

A moderate southeast to south swell from former Tropical Storm Ivo
will affect the waters through early Tue. Swell will likely peak 
between 3 and 5 feet. A swell from this direction could cause some
surges around and inside vulnerable harbors, especially Avalon 
and San Pedro/Long Beach. Moderately large breaking waves near the
coast are possible, capable of capsizing small drifting boats.

&&

.BEACHES...25/133 PM.

Former Tropical Storm Ivo, currently about 450 nautical miles WNW
of Cabo San Lucas, will generate a southeasterly to southerly 
swell which will bring elevated surf to south facing beaches
through Tuesday. 

The peak of the swell across the coastal waters should occur this
afternoon through Monday morning at between 3 and 5 feet with a 
period of between 11 and 14 seconds. 

Surf heights are expected to average 4 to 6 feet on south facing 
beaches of Los Angeles and Ventura Counties. Dangerous rip 
currents are likely, as are large breaking waves on rock jetties.

There is a low risk of minor tidal overflow near the times of 
high tide on susceptible low lying beaches. The highest tides 
will be late in the afternoon and evening today and Monday, and 
should reach 5.7 to 6.7 feet. There may be some beach erosion as
well.

&&

.FIRE WEATHER...25/315 PM.

A ridge of high pressure has built over the region and will 
persist through much of this week. This will maintain very warm 
conditions, with maximum temperatures generally in the 94 to 104 
degree range over the valleys, mountains, and deserts. Minimum 
humidities will generally range between 10 and 25 percent across 
interior sections much of this week, with isolated single digit 
readings at times in the Antelope Valley and Los Angeles county 
mountains. Some mountain locations will also have moderately poor 
overnight recoveries between 20 and 40 percent. Southwest to 
northwest wind gusts between 20 and 30 mph will be common at times
over interior areas, with isolated gusts up to 40 mph near Lake 
Palmdale. Northwest to north winds will generally gust between 20 
and 30 mph each evening across the western portions of the Santa 
Barbara south coast and foothills, potentially increasing slightly
later in the week. All of this will result in elevated fire 
weather conditions over interior areas much of this week.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through Tuesday morning for
      zones 40-41-87. (See LAXCFWLOX).
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (WED-SUN).

No significant hazards expected.

&&

$$

PUBLIC...Sirard/Rorke
AVIATION...Rorke
MARINE...Sweet
BEACHES...Sweet/DB
FIRE...Gomberg
SYNOPSIS...Kj

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