Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 300559
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1059 PM PDT Sat Apr 29 2017

...Aviation discussion updated...

.SYNOPSIS...

Offshore flow will bring fair skies and above normal temperatures
Sunday. On Monday the onshore flow will bring an overnight marine
layer and cooling to the Los Angeles coast... otherwise fair skies
and above normal temperatures will continue through Thursday. Low
pressure will approach the region on Friday and may result in
increased cloudiness.

&&

.SHORT TERM...(SAT-TUE)

Satellite imagery showing clear skies across the district this
evening. Gusty Santa Ana winds have diminished considerably
this evening, and are mainly confined to the mountains and
foothills. Winds have reversed to onshore across the coast and
portions of the coastal valley. Weak offshore flow will begin the
day on Sunday (with LAX-Daggett gradient expected to be -2.5 mb)
then transition to weak onshore in the afternoon. Look for another
very warm day across interior sections on Sunday, with warmest
valleys expected to climb to around 90 degrees. Immediate coastal
areas expected to see some cooling on Sunday due to lack of
offshore winds and an earlier return of the sea breeze.

*** From previous discussion ***

For Sunday night and Monday, high resolution models continue to
indicate an eddy spinning up over the bight. If this develops as
forecast, some stratus/fog will be likely across the LA coastal
plain and southern coastal waters. So, will keep stratus/fog in
the forecast. Other than this potential stratus, skies should
remain mostly clear across the area Sunday night/Monday. As for
temperatures on Monday, coastal/valley areas of Ventura/LA
counties will cool a few more degrees. However, interior sections
will warm a couple of degrees as well as the Central Coast (due to
a little offshore push Monday morning).

For Monday night/Tuesday, 12Z models indicate little change in any
parameters. So, will go with a relative persistent forecast: clear
skies except for some LA county coastal stratus and little change
in temperatures from Monday.

.LONG TERM...(WED-SAT)

Overall, 12Z models continue to exhibit good synoptic agreement
through the period. At upper levels, ridge will move across the
district Wednesday/Thursday with a unseasonably potent trough
developing along the West Coast Friday/Saturday. Near the surface,
weak diurnal flow prevails Wednesday/Thursday then onshore flow
reestablishes on Friday/Saturday.

Forecast-wise, Wednesday/Thurday look to be rather benign days.
With upper ridge over the area on Wednesday and to the east on
Thursday, skies should remain mostly clear although some
night/morning stratus will be possible across southern areas.
Temperatures will remain above seasonal normals with Wednesday
likely the warmest day with some slight cooling on Thursday. No
wind issues are anticipated Wednesday/Thursday.

For Friday/Saturday, things start to change. Through the
Friday/Saturday time frame, sharp upper trough will approach the
West Coast and develop a closed low off the Central Coast on
Saturday. With this pattern, onshore flow will be on the increase
which should allow for an increase in night/morning stratus/fog
across the area (especially on Saturday morning). Outside of any
stratus, mid/high level clouds will be on the increase as trough
approaches, but things will remain dry. So with stronger onshore
flow and more cloud cover, temperatures will be exhibiting a
cooling Friday and even more so on Saturday.

&&

.AVIATION...30/06z.

At 03z at KLAX... There was a surface based inversion. The top was
around 400 feet with a temperature of about 21 degrees Celsius.

Overall... High confidence in the current TAFs. There is a less
than ten percent chance of MVFR conditions developing along the
Los Angeles County coastal sites toward morning and a fifteen
percent chance of IFR/MVFR conditions developing Monday morning.
Otherwise and elsewhere VFR conditions will prevail.

KLAX... High confidence in the current TAF. There is a less than
ten percent chance of MVFR conditions developing toward morning
and a fifteen percent chance of IFR/MVFR conditions developing
Monday morning. Otherwise VFR conditions will prevail. Any east
winds will be 7 knots or less.

KBUR... High confidence in the current TAF. VFR conditions will
prevail.

&&

.MARINE...29/830 PM.

Moderate confidence in low-end (winds to 25 KT) Small Craft
Advisory (SCA) conditions for west to northwest winds through
this evening over the Santa Barbara Channel and Santa Monica
Basin. Otherwise SCA conditions will likely persist across
the outer waters through Tuesday or Wednesday. The SCA will
likely be extended each day.

Due to the gusty winds...choppy seas should be expected in most
areas (including near shore) into next week.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until midnight PDT tonight for
      zones 650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Monday for
      zones 670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(TUE-SAT)
No significant hazards expected.

&&
$$

PUBLIC...Thompson
AVIATION...Kj
MARINE...Gomberg/Kittell
SYNOPSIS...STu

weather.gov/losangeles



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