Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
306 am PST Friday Feb 12 2016
an upper level trough passing to the north will provide brief
cooling to the region by Saturday. High pressure aloft building
in from the west and a return of offshore winds will allow
temperatures to rebound to near record territory by Monday. A
second more significant area of low pressure should bring a chance
of precipitation to the forecast area later this week.
A weak upper trough was bringing some middle-high level clouds across
much of slo/sba County this morning. This upper trough will bring
some rain to the northern part of the state today...but just keep
high clouds moving over the region today. With the offshore
gradient weakening...some dense fog has developed across the
central coast and the adjacent coastal waters this morning. There
is a slight chance that some patchy dense fog could develop across
portions of the Santa Barbara South Coast. Not expecting any
stratus to form over l.A and Ventura County this morning due to
the weak offshore flow. The fog that is across portions of the
central coast should scour out early as some easterly flow from
the san Lucia mountains will pick up later this morning. High temperatures
will continue to trend a few degrees cooler across coast and
valleys as the offshore flow continues to weaken and the upper
ridge shifts over to a weak trough over the area late today. The
seabreeze will pick up this afternoon giving coastal areas the
best cooling. High temperatures will remain well above normal for areas
away from the immediate coast. Expect highs to reach the upper 70s
to a few 80s along the la/vtu coastal zones...while the valleys
warm into the middle 80s with a few sites reaching the upper 80s.
High temperatures will be a bit cooler for areas north of Ventura County.
The forecast for tonight will be a bit trickier in respect to low
clouds and stratus. The surface offshore/onshore gradient will be
near neutral tonight into Saturday morning. So stratus will be
able to creep a bit closer to the la/vtu coast. Have put a return
of low clouds and fog to the central coast and a chance for some
patchy dense stratus across portions of the l.A /vtu and possibly
the sba South Coast late tonight into Saturday morning. More
marginal widespread cooling will continue as a weak upper level
disturbance moves over the region Saturday. The only visible
affects will be some high clouds moving over the region with the
cooler temperatures. By Saturday evening...northerly winds will increase
behind the exiting upper disturbance. Expect gusty northwest-north winds to
increase across the sba County mountains and wind prone passes and
canyons of the sba South Coast Saturday evening through the overnight
hours. Also...across the I-5 corridor into the Santa Clarita and
San Fernando valleys. Winds will remain below Wind Advisory
For Sunday...skies will be mostly sunny with winds continuting in
the same areas...but wind down over sba County. There could be
some local gusty winds below the Hollywood Hills and Santa Monica
Mountains where the Marathon runners will be Sunday morning. Not
expecting any stratus Sunday morning due to the offshore winds.
High temperatures will rebound as well 4 to 8 degrees for coast and
coastal valleys as offshore flow kicks in.
By Monday...a rather strong 589dm high sets up just off the
southern and central coast with a weak cutoff low just to the SW
of the high. At the surface...a relatively strong offshore
surface gradient sets up as a 1030mb high builds in over northern
Nevada. This will translate to warmer temperatures and a moderate Santa
Ana wind event. Lax-dag surface gradient was -6.8mb. Some upper support
over the mountains...but not much over coast and valleys. By
Tuesday the upper ridge axis will weaken but persist overhead
while another upper trough starts to dig south towards northern cal.
High temperatures will remain close to monday's for areas S of Point
Conception...but should see some minor cooling for areas to the
north. Expect highs for la/vtu coast and coastal valleys to be in
the middle to upper 80s...with cooler conds for areas to the north
and interior locations.
By Wednesday...a broad trough with a more significant cold front
will move into northern California...then slide south to bring
rain into the forecast area by Wednesday night or Thursday. With
the models consistent in the slow down of the approaching storm
have backed off probability of precipitation 6-12 hours. Looks like the brunt of the storm
will be Thursday into Thursday night...with possible residual
showers into Friday. Too early to get a handle of rainfall
amounts...but looks like the snow level will begin above 6500
feet...then lower to between 5500 and 6000 feet Thursday-Thursday
night. High temperatures will only reach the middle 70s Wednesday...with
even cooler conds on Thursday with the rain.
At 06z...the marine layer depth at klax was around 300 feet deep.
The top of the inversion was located around 1100 feet with a
temperatures of 25 degrees celsius.
Areas of low clouds and dense fog will affect the central coast
and Santa Ynez Valley overnight...with IFR to LIFR conds.
Elsewhere...some low clouds with IFR conds are possible across
coastal sections of southern sba...vtu and l.A. Counties...mainly near
the beaches...but confidence in this is low. Expect low clouds
with IFR to LIFR conds to spread into most coastal sites Friday
evening after 00z.
Klax...moderate confidence in the 06z taf. There is a 30 percent
chance of MVFR visibilities between 10z and 16z...and a 10 to 20 percent
chance of IFR to LIFR conditions during that time. There is a
20 to 30 percent chance that IFR conds Friday evening will hold off
until 05z or 06z. Any east winds should remain less than 5 knots.
Kbur...high confidence in the 06z taf with VFR conditions
expected through the period. No wind issues are expected at this
A shallow marine inversion will bring areas of dense fog with
visibility one nautical mile or less...mainly for the northern
waters. Patchy dense fog with visibility one nautical mile or
less is likely across the remaining coastal waters through Friday
Otherwise...northwest winds will increase through Friday
afternoon. Small Craft Advisory conditions are likely for the
northern outer waters. There is a chance that the Small Craft
Advisory may need to be expanded south into zone 676 for Friday
night and into Sunday. Small Craft Advisory for hazardous sea
conditions with swells building over 10 feet is likely from Piedras
Blancas to San Clemente Island excluding the inner basins south of
Point Conception tonight and persists through Sunday. There is a
chance swells will build to near 10 feet in the Santa Barbara
basin Friday night.
California...dense fog advisory in effect until 9 am PST this morning for
zones 34-35. (See laxnpwlox).
High surf advisory in effect until 9 am PST Sunday for zones
34-35. (See laxcfwlox).
Beach hazards statement in effect from 9 am PST this morning
through Sunday morning for zone 39. (See laxcfwlox).
High surf advisory in effect from 9 am this morning to noon
PST Sunday for zones 40-41-87. (See laxcfwlox).
Pz...Small Craft Advisory for hazardous seas in effect until 9 PM
PST Sunday for zone 645. (See laxmwwlox).
Small Craft Advisory in effect until 3 am PST Monday for
zones 670-673-676. (See laxmwwlox).