Scientific Forecaster Discussion
fxus66 klox 101212
Area forecast discussion...updated
National Weather Service Los Angeles/Oxnard California
412 am PST Mon Dec 10 2018
There will be elevated winds, cooler temperatures, and a slight
chance of precipitation on the north slopes of the Ventura and
Los Angeles County mountains Monday night and Tuesday. Another
slight chance of precipitation will develop across the region next
weekend. Otherwise dry and slightly warmer conditions will prevail.
Short term (tdy-wed)...10/314 am.
Yesterday's ridge will give way to a trof today. Plenty of mid and
high level clouds will keep skies partly to mostly cloudy. There
is 3 mb of offshore flow from both the north and east which will bring
some gusty canyon winds but since there is no upper of thermal
support the winds will not reach advisory criteria. The offshore
flow will allow Max temps across the coasts and vlys to remain
above normal although the falling hgts will knock a degree or two
off of the temps compared to ydy.
A decent meso sfc high will develop near kbfl setting up stronger
north flow and along with the cooler air spilling in behind the
later afternoon trof passage a low end Wind Advisory will set up
thru the I-5 corridor and the sba South Coast and perhaps the in
the vlys along the la/vta border. The north winds will also create
enough orographic lift up the north sides of the mtns near the
Kern County line to form clouds and slight chc of showers.
Skies will clear with the dry northwest flow on Tuesday. At one point
the trof was supposed to bring much more cool air with it but now
not as much is forecast. The interior will cool some but there
will be little change in temps from Monday across the coasts and
vlys as the compressional heating counteracts the cooler air.
Wednesday is setting up to be a very nice day as a ridge moves
into the area. The higher hgts will combine with sunny skies and
weak offshore flow to bring 2 to 4 degrees of warming to Southern
California. Max temps will end up 3 to 5 degrees above normal.
Long term (thu-sun)...09/250 PM.
The ec and GFS are in good agreement thru Thu, then differences show
up Fri thru sun. Upper level ridging will continue on Thu. An upper
level trof moving thru the east pac will approach the California coast on Fri,
with the GFS weaker and ec stronger with this system, altho dry
weather should prevail thru Fri across SW California.
The ec brings a front and fairly decent rain into the area Fri
night and Sat morning while the GFS dissipates the front with dry
weather during the period except for a slight chance of showers
over far northwest slo County Fri night. Decided to lean more toward the
GFS for this time frame.
The ec and GFS both agree to some extent on pushing another upper
level trof and surface frontal system into the area on sun, with
the ec faster than the GFS with this system. Also leaned more
toward the GFS with a slight chance to chance of rain moving
mainly into slo/sba counties on sun.
There is really low to moderate confidence in the forecast for
the Fri night thru sun timeframe given all the model differences
in speed and strength of the two weather systems. Additional model
runs will be needed to fine tune the pcpn fcst during the period.
The ec and GFS agree that there will be good offshore gradients
Wed night into Thu with the potential for advisory level winds in
the usual offshore wind-prone areas of vtu/l.A. Counties. Gusts up
to 35 to 45 mph will be possible.
Temps will be several degrees above normal for many of the coast and
vlys Thu, then cool to slightly above normal Fri. It looks like
temps will cool to near normal for the most part Sat and sun.
At 12z, there was no marine layer depth at klax.
Moderate-to-high confidence in the current forecast. There is a
chance of LIFR conditions at north of Point Conception through
17z, and again after 08z.
Klax...VFR conditions are expected through at least 10z. LIFR
conditions are possible Tuesday morning. Any east winds are
expected to remain less than 7 knots.
Kbur...VFR conditions are expected throughout the period. No wind
issues are expected at this time.
Moderate-to-high confidence in the current forecast. Less
confidence for the inner and nearshore waters, higher confidence
for the outer coastal waters. Northwest flow along with building
seas will develop through this evening. A mix of gusty winds and
hazardous seas is expected for the outer waters, but less of a
chance exists for the nearshore waters north of Point Sal. There
is a 40 percent chance of Small Craft Advisory conditions
developing across the Santa Barbara Channel between 3 PM today and
3 am tonight, and a 10 percent chance of similar conditions for
the inner waters south of Point Mugu to San Mateo Point.
Winds will likely increase some for Tuesday, increasing chances
for a mix of gusty winds and hazardous seas Tuesday afternoon and
An extended period of hazardous marine conditions is possible
Thursday and into the weekend, especially for the outer coastal
waters. There is an outside chance of a very large swell
affecting the coastal waters over next weekend.
A high surf advisory remains in effect for the beaches along the
central coast and Ventura County. Local advisory sets are possible
at west facing beaches along the South Coast of Santa Barbara
County, such as Rincon Point and County line this afternoon and
An extended period of high surf is expected at central coast
beaches for the latter part of the week. Very large and
potentially damaging surf could develop over the weekend and into
early next week with energy possibly pushing into Southern
California bight early next week.
California...high surf advisory in effect until noon PST Tuesday for zones
34-35. (See laxcfwlox).
High surf advisory in effect from noon today to 6 PM PST
Tuesday for zone 40. (See laxcfwlox).
Pz...Small Craft Advisory in effect from 9 am this morning to 9 am
PST Tuesday for zones 645-670-673-676. (See laxmwwlox).
Hazard potential outlook (wed-sun).
Gusty advisory level north to northeast winds are expected
Wednesday night into Thursday. High surf and dangerous rip
currents are expected on the central coast Thursday through
Saturday, possibly expanding to most beaches on Saturday.