Scientific Forecaster Discussion
fxus66 klox 230030 aaa
Area forecast discussion...updated
National Weather Service Los Angeles/Oxnard California
430 PM PST Fri Nov 22 2019
Updated aviation discussion
A high pressure system combined with offshore flow will bring
warm and dry conditions to most areas through Sunday. Locally
gusty winds are possible over wind prone areas during this time.
Rain and low elevation snow is likely next week as an unseasonably
cold low pressure system moves over the region.
Short term (tdy-mon)...22/201 PM.
Still enough lingering moisture and southerly flow to generate
some afternoon clouds, mainly over the higher terrain. Otherwise
plenty of sunshine with temps a few degrees warmer than Thursday.
Gradients continue to trend offshore ahead of our weak to moderate
Santa Ana wind event and with weak ridging coming in aloft temps
over the weekend will warm up several degrees, topping out in the
low to mid 70s in most lower elevation locations. The most favored
locations in la/Ventura counties will likely see some advisory
level wind gusts but most areas should remain below advisory
Strong onshore trends Monday ahead of the next trough moving into
the pac northwest will result in a cooler day with highs back down to
normal or even slightly below normal. As the trough moves down
into the Great Basin later Monday a pretty good northerly push
will develop, likely generating some advisory level winds in the
Santa Barbara area and i5 corridor as well as the Antelope Valley.
Long term (tue-fri)...22/223 PM.
Tuesday will be the last dry/quiet day before a lengthy period of
cold/wet conditions begins Tuesday night and lasts through the end
of the week and possibly into next weekend. Models are in very
good agreement now that a deep upper level trough will develop
over the West Coast Wed-Fri. It's not tapping into an Arkansas but
there's ample moisture and cold air aloft to generate periods of
moderate to locally precipitation through that period. The cold
air aloft (as low as -34c at 500mb) will likely help spawn some
thunderstorms and lower snow levels to as low as 2000'.
This almost certainly will cause significant disruptions to all
forms of travel to/from/around so cal, including over the
Grapevine where accumulating snow may force roadway closures as
early as Wednesday afternoon. Burn areas will also be at risk for
debris flows, mainly due to the threat of thunderstorms. Early
estimates for rain amounts through the Holiday period range from
1-3" for coast/valleys and 3-5" for the foothills and Lower
Mountain elevations. Higher elevations will likely see significant
snow accumulations, in excess of one foot in many areas.
Precipitation will become more showery (hit and miss) in nature
Thursday night into Friday but still heavy at times in
At 2330z, at klax there was a weak inversion at 500 ft deep. The
top of the inversion was at 1000 ft with a temperature of 16 deg
High confidence in the current forecast. VFR at all terminals
through the forecast period with the exception of a 40% chance of
IFR/LIFR fog at kprb 12-16z Saturday. Gusty NE to east winds are
expected at kcma and koxr later Saturday morning through the
Klax...high confidence in VFR conditions. Any east winds Saturday
morning should remain less than 7 knots.
Kbur...high confidence in VFR conditions through the taf period.
Outer waters...less than Small Craft Advisory (sca) level winds
through Sunday morning. There will be a 30% chance for Small Craft Advisory level
gusts Sunday afternoon then across the entire outer waters Sunday
night into Monday. There is a 70% chance for gale force winds
across the northern outer waters Monday afternoon to Tuesday with
Small Craft Advisory level winds and seas continuing for the remainder of the
outer waters through at least midweek.
Inner waters north of Point Sal...should remain below Small Craft Advisory levels
through Monday morning. There is a 30% chance for Small Craft Advisory offshore
winds Saturday morning and again Sunday morning. About a 60%
chance of Small Craft Advisory conditions developing Monday afternoon through
Inner waters S of Point Conception...there will be a 30% chance
for Small Craft Advisory offshore winds across the inner waters between Ventura to
Malibu Saturday morning, with a 40% chance for the same area
Sunday morning. Small Craft Advisory conditions may develop late Monday through
There will be an increasing northwest swell approaching 12-17 feet
from late Monday through Tuesday night affecting the outer
California...high surf advisory in effect from 2 am Saturday to 8 am PST
Sunday for zones 34-35. (See laxcfwlox).
Hazard potential outlook (mon-fri).
Gusty north winds possible in some areas Monday into Tuesday
morning. A significant winter storm is expected Tuesday night
through Friday with periods of heavy rain, thunderstorms, and low
elevation snow causing major travel disruptions along with
possible mud and debris flows near burn areas.