Area Forecast Discussion
Issued by NWS Los Angeles, CA
FXUS66 KLOX 242038
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
138 PM PDT SUN JUL 24 2016
High pressure across the southwest U.S. and onshore flow will
support near to slightly above normal temperatures through most of
the next seven days with a return of night to morning low clouds
to coastal and valley areas. An influx of monsoonal moisture may
bring thunderstorms across interior areas late next week.
A strong onshore trend in the gradients has resulted in
significant cooling in most locations today as expected.
Temperatures are generally down 5-15 degrees, with the biggest
cooling occurring in the valleys. Visible satellite imagery still
showing some low clouds hugging the coast in a few places, in
particular the SBA south coast and the Central Coast. Still
possible that these areas will clear out later this afternoon.
The marine layer stratus will continue to become better organized
tonight. Soundings this morning suggested a marine layer depth
around 400-800 feet. The marine layer should deepen a few hundred
feet tonight, especially south of Pt. Conception where the eddy
will help. This could allow the low clouds and fog to spread into
the coastal valley areas in LA and Ventura counties. Some dense
fog can`t be ruled out, especially on the Central Coast. Hard to
say what the marine layer will do after tomorrow morning, but
minor changes are expected.
Temperatures will remain near or slightly above normal tomorrow,
followed by several degrees of warming for inland areas on
Tuesday and Wednesday as high pressure over the Four Corners
region starts to expand west again. However, some mid and high
level clouds associated with a surge of monsoonal moisture could
offset the warming on Tuesday and Wednesday. The NAM suggests a
surge of low-level moisture (850 mb dewpoints greater than 8C)
reaching northern SLO County by Tuesday evening. However, most of
the moisture remains over the coastal waters and there is no
instability associated with it, so thunderstorms will not be an
issue through mid-week.
The main forecast concern in the long term will be the
possibility of monsoonal thunderstorms. The current forecast has a
slight chance starting on Friday for the LA/Ventura mountains and
the A.V., but based on the 850 mb dewpoints with the latest model
runs, it looks like the better chance for thunderstorms will be
over the weekend (still only a slight chance at this point
Temperatures will likely remain near or slightly above normal
through the end of the week, then some cooling will be possible
over the weekend with the increase in monsoonal moisture. An
easterly wave rotating around the southern fringe of the Four
Corners high may result in some lower height/thickness values as
At 16Z at KLAX, the inversion was around 1200 ft deep. The top of
the inversion was near 4600 feet with a temperature of 27 degrees
S of Point Conception...Low to moderate confidence with 18z tafs.
A southerly push will keep LIFR cigs across KSBA through 17-18z.
Otherwise IFR to low MVFR conds will remain right off the coast.
Expect a stronger eddy to develop this evening allowing for higher
cigs to develop over coastal areas. Better confidence that KBUR
and KVNY will get IFR cigs as well but after 11z. There is a 30%
chance that KBUR/KVNY will not get cigs. Lower confidence in
respect for the timing of stratus developing and scouring out +/-
N of Point Conception...Moderate confidence with LIFR/IFR cigs to
push in across KSMX and KSBP after 06z and 09z respectively. Cigs
could be +/- 1 hour from Taf. 40% chance for KPRB to receive LIFR
cigs after 12z.
KLAX...Low to Moderate confidence in the 18z taf. Smoke should
not be much of a factor as Mean winds will be out of the SW. The
lower confidence is in regards to the timing of the stratus
returning. Model guidance seems too late. Best guess between
05-09z for IFR/MVFR conds. Higher confidence with MVFR cigs after
KBUR... Moderate confidence with 18z taf. Smokey conditions should
let up going into this afternoon with SW steering winds from the
fire. With a strong eddy expected, IFR to low MVFR cigs should
make it in to KBUR and KVNY. Although there is a 30% chance this
may not occur. Expect cigs between 11z-15z
Not expecting any small craft advisories through at least
Wednesday. There will be some gusty NW winds across the NW portion
of the northern zone PZZ670 through this afternoon. A strong eddy
will develop overnight into Monday morning across the SoCal
bight. Sustained winds as high as 12 kt will be possible.
Especially across the San Pedro Channel both early Sunday and
There will be patchy dense fog with visibility 1 nm or less
through mid afternoon off the central coast. The eddy should
allow for better visibility across the inner waters of Los
Angeles, Ventura and Santa Barbara counties through this
Red flag warning continues for the Los Angeles County mountains
through 2200 PDT today. A moderate onshore pressure gradient will
become weak this evening and the winds 15 to 25 mph with local gusts
to 35 mph will prevail in the vicinity and through the soledad
canyon area. The relative humidity trended 10-15 percent higher
and temperatures 10-15 degrees cooler than Saturday at this time.
Temperatures monday morning will differ little from this morning
and continue 5-10 degrees above normal. Tempertures will vary
plus or minus a couple of degrees each day and likely remain 5-10
degrees above normal through the week. RH will trend higher as
moisture pushes north through the period and overnight RH will
range 25-35 percent in the warmer interior sections with mid teens
in the afternoon. Slight chance of thunderstorms are expected over
the Ventura and Los Angeles County mountains Friday through Sunday
with a LAL of 2.
CA...Red Flag Warning in effect until 10 PM PDT this evening For
zone 254. (See LAXRFWLOX).