Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
335 am PST Thursday Dec 18 2014
..updated aviation section...
A weak storm system will bring the chance of some light rain to the
area this morning. On Friday...yet another weak system will brush
the area...but any chances of light rain should remain confined to
northern sections. For Saturday through the first half of next
week...high pressure will build over the area...bringing dry
conditions and a warming trend.
Short term (today-sat)...
in the immediate short term...weak short wave is diving down across
the area...generating some very light showers this morning. Pretty
much everywhere will have a chance of some liquid hitting the ground
this morning...so will continue with chance/slight chance probability of precipitation for
all areas. Rainfall amounts will be light...generally under
one tenth of an inch. By this afternoon...weak ridging will build
in...and precipitation threat should end.
For tonight/Friday...models indicate another weak system will
flatten the ridge...and generate the possibility of some light
showers Friday/Friday evening across San Luis Obispo and Santa
Barbara counties. So...for these areas...a slight chance of showers
will continue...with only very light amounts anticipated. Would not
be surprised to see some sprinkles/light showers work their way down
to Ventura/Los Angeles counties...but not enough to warrant any
mentionable precipitation chances at this time.
On Saturday...upper ridge will once again begin to build in from the
southwest...ending the threat of any precipitation for the area.
As for temperatures...a gradual warming trend is expected through
the short term...with most areas around seasonal normals by
Long term (sun-wed)...
for the extended...models are in good synoptic agreement and rather
benign weather can be expected. Main feature will be the upper ridge
building in from the southwest...which will peak in strength on
Monday then gradually weaken Tuesday/Wednesday. Near the surface
some offshore flow will develop...northerly Saturday night/Sunday
then turning more northeasterly Monday/Tuesday.
With this pattern...dry conditions are expected through the period.
Temperatures will show a nice warming trend through Tuesday...then
cool slightly on Wednesday. In fact by Tuesday...most coastal/valley
areas should in the 70s to lower 80s. With the northerly gradients
Saturday night/Sunday morning...there may be some decently gusty
northerly winds across the Santa Ynez range (possibly reaching low
end advisory criteria). Otherwise...any offshore winds the first
half of next week are expected to remain light.
There is no inversion near klax at 1130z.
Moderate confidence in the 06z taf package. Scattered light showers
will reach la County early this morning...but will continue to
weaken as they move southeast. Kept most sites IFR other than ksbp
and ksmx for a couple hours this morning...but there is a 20-40
percent chance of MVFR ceilings or visby pretty much anywhere through
about 18z. Coastal sites have the best chance of MVFR conditions
tonight through 18z Thursday.
Klax and kbur...moderate confidence that IFR conditions will persist
through most of the period. 30 percent chance of MVFR ceilings/visby
14-18z with the passage of a weak front that most likely will not
result in any rain.
Good confidence that there will be no Small Craft Advisory winds until late Saturday
afternoon and Sunday evening. The marginal Small Craft Advisory for hazardous seas
was extended through 3pm this afternoon for the two northern outer
water zones...as seas will hover at or just below 10 feet. Local 10
foot seas will be possible in the western portions of pzz645 and
pzz676. Good confidence that a large...long period northwest swell will
enter the outer coastal waters and pzz645 late Friday night. This
may result in large breaking waves at Harbor entrances on the
central coast...namely Morro Bay Harbor.
Small Craft Advisory (see laxmwwlox).
Beach hazards statement (see laxcfwlox).