Area Forecast Discussion
Issued by NWS Los Angeles, CA
FXUS66 KLOX 291801
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1101 AM PDT MON AUG 29 2016
Warm afternoon temperatures through tomorrow will be followed by a
cooling trend into the weekend. The marine layer will be minimal for
the next two overnight periods with only a few clouds along the
Central Coast and portions of Los Angeles County. The clouds will
push farther onshore and into the adjacent valleys by the weekend.
Very little stratus in the area this morning...primarily over the
central coast region of Santa Barbara County and around Morro
Bay. Winds have calmed and no stations are over 30 mph at this
time, but expecting them to pick up again this afternoon. The appreciable
change to the pattern today will be the rising heights which will
drive the temperatures up. The only area unchanged in heating from
yesterday is along the central coast in the areas under the marine
layer clouds. Elsewhere it is already about two degrees warmer at
the coasts to five degrees in the valleys and mountains. The
increased heat and continuing afternoon winds will raise the fire
weather danger in Santa Barbara County to a Red Flag Warning.
*** from previous discussion ***
Max temps are the big deal today. Srn Ca will be under the axis
of ridge with 592DM hgts over the area. Temps will be up another
few degrees from Sundays numbers. Max temps will be above normal
everywhere save for the beaches of the Central Coast. Other
coastal areas will be only a few degrees above normal but the vlys
and inland areas will be 8 to 12 degrees above normal.
Another sundowner tonight will likely need a 9 hour wind advisory.
Low clouds again will be confined to the central coast.
The ridge moves off on Tuesday as a Pac NW trof moves eastward.
There will be some cooling over SLO and SBA counties as hgts fall
but south of Pt Conception max temps will be the same or even a
degree higher than today.
Broad trofing sets up over the west coast on Wednesday. But really
only the weakest tail of the trof will be over Srn Ca. Its effects
will not be that strong. The marine layer cloud deck will only
reform a little and the onshore trends will be weak. So there will
be some cooling but not much.
Both the GFS and the EC agree that the upper trof will persist
through the extended period and will strengthen a little each day.
The NAM suggests only a limited marine layer stratus deck on
Thursday and since the trof still not that impressive at the time
this forecast makes sense. So not quite as much cooling as
Friday and the Weekend look pretty grey as the trof increases to
the point where it will lift the marine layer deep into the vlys.
Look for night through morning low clouds and fog extending all
the way into the Santa Clarita vly. Max temps will quickly cool to
normal or even blo normal with the biggest drop occuring in the
vlys. Cooler still on Saturday due to lower hgts and then little
change for Sunday.
AT 1720Z, the marine layer depth at KLAX was 500 feet. The top of
the inversion was near 2700 feet with a temperature of 29 degrees
Low confidence in 18Z TAFs for KLAX KLGB KSMX and KSBP. There is
a 50 percent of IFR cigs at KLAX and KLGB between 11Z and 17Z. IFR
cigs expected to begin anytime between 30/08Z and 13Z with a 40
percent chance that VFR cigs prevail. There is a 30 percent chance
of LIFR to VLIFR cigs/vsbys at KSMX after 30/06Z. There is a 30
percent chance of MVFR haze at any coastal TAF site after 30/06Z.
Good confidence in remainder of the TAFs.
KLAX...Low confidence in the 18z TAF. There is a 40-50 percent
chance of VFR conditions lasting through Tuesday.
KBUR...High confidence in CAVU TAF.
The Gale Watch for zones 670 and 673 has been converted to a Gale
Warning beginning early this evening and continuing through
Tuesday night. The Gale Watch for zone 676 has been converted to a
Gale Warning beginning late Tuesday afternoon and continuing
through Tuesday night. Small Craft Advisories remain in effect for
the outer waters before the winds increase to Gale criteria.
Small Craft Advisories remain in effect for zones 645 and western
portions of 650 for this afternoon through late tonight. Another
round of Small Craft Advisories are expected for these areas again
Tuesday afternoon through Tuesday night.
Patchy dense fog is possible at times across all waters through
Wednesday morning. The patchy dense fog is mostly likely to occur
during the overnight to morning hours across the outer waters from
Point Pierdas Blancas to Catalina Island and to the south and west
of Palos Verdes.
Gusty sundowner winds are expected across southern Santa Barbara
county this afternoon/evening and again Tuesday afternoon/evening.
Wind gusts around 40 MPH are expected through and below passes and
canyons. Along with the winds...relative humidity is expected to
fall into the teens and single digits late this afternoon/evening
and again Tuesday afternoon/evening with poor overnight
recoveries. So, an extended period of critical fire weather
conditions are expected late this afternoon/evening and again late
Tuesday afternoon/evening and the Fire Weather Watch has been
upgraded to a Red Flag Warning.
Elsewhere across the area, hot and dry conditions will prevail and
there will be elevated fire danger across inland areas through
Tuesday. The warming temperatures will cause steepening lapse
rates that will enable deep vertical mixing layers, especially
today and Tuesday when mixing layer heights could range between
12,000 and 15,000 feet. For existing fires or new ignitions over
interior areas, plume dominated fire behavior will be possible.
CA...Red Flag Warning in effect from 5 PM this afternoon to 10 AM
PDT Wednesday For zones 239-252. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
AM PDT Wednesday For zones 645-650. (See LAXMWWLOX).
Small Craft Advisory in effect until 6 PM PDT this evening
For zones 670-673. (See LAXMWWLOX).
Gale Warning in effect from 6 PM this evening to 3 AM PDT
Wednesday For zones 670-673. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 PM PDT Tuesday For
zone 676. (See LAXMWWLOX).
Gale Warning in effect from 3 PM Tuesday to 3 AM PDT
Wednesday For zone 676. (See LAXMWWLOX).