Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
830 PM PDT Friday may 22 2015
Overnight low clouds are expected through the weekend and into next
week. Temperatures will gradually warm a couple degrees by
Monday...yet still remain below normal. A ridge of high pressure
will bring slightly above normal temperatures by the end of next
Short term (tonight-mon)...upper low continues to move east into
Arizona tonight. Considerable low level moisture lingers across
Southern California with satellite imagery showing low clouds
filling in quickly this evening across much of Los Angeles and
Ventura counties. 00z NAM model cross section showing moist layer as
deep as 10,000 feet across Los Angeles County this evening. The middle
and upper level flow remains from the north tonight with still a
slight chance of some light showers streaming in from the north
across the north facing mountain slopes and Antelope Valley. In
addition...low level south-southwest flow combined with ample low
level moisture will continue to keep a slight chance of light
showers tonight across the coastal slopes and foothills of the San
Gabriel Mountains and adjacent San Gabriel valley. Locally breezy
below passes and canyons tonight with the north flow but below
Precipitation chances expected to diminish on Saturday. However...continued
low level moisture with heating should continue to generate quite a
bit of stratocumulus clouds...especially across Los Angeles County
mountains and valleys. Otherwise...most other areas should see
partly cloudy skies with temperatures up a few degrees...but still cooler
*** From previous discussion ***
Models showing another piece of energy dropping south through
interior California Sat night into early Sunday. The bulk of the
moisture with this system remains well east of our area so really
not much risk for any precipitation locally unless it drifts farther west,
but likely some clouds over the mountains and a delay in our warmup.
Current forecast brings a solid marine layer return Sunday morning but
given how things have gone lately and probably just minimal boundary
layer warming at best it's hard to envision much change in the
marine layer pattern through the weekend (ie. Patchy/random).
Most areas should see at least a few degrees of warming Monday with
heights rising. Models not in great agreement on the amplitude of
the ridge but all agree that at least minor warming is expected
Monday. There may be just enough lower level warming to help support
a more solid marine lyr, but things haven't gone our way in that
department lately so we'll see how that GOES.
Long term (tue-fri)...a little dry trough will swing through the West
Coast Tuesday/Wed, which likely won't do much other than maintain the
status quo. By Thu, though, there is solid model agreement both in
the 12z runs and earlier runs, that we will be seeing a fairly
strong ridge developing Thursday/Friday for much better warming and temperatures
finally climbing to above normal levels again which should at least
carry into Sat.
At 2330z...there was no marine inversion at lax.
Low confidence in the 00z taf forecast package. Considerable low
level moisture lingering across much of the district this afternoon
has generated solid deck of stratocumulus clouds across interior
sections of the forecast area with better clearing near the coast.
Once sun GOES down...still questionable how much and timing of
stratus tonight into Saturday morning due to lack of marine
inversion. For areas where ceilings develop...should mostly be in MVFR
to VFR catgegory. With deep moist layer continuing still a 10
percent chance of light showers overnight into Saturday morning
across la County. Gusty southwest to west winds will continue
through period at kwjf and kpmd.
Lax...low confidence with 00z taf with respect to timing and height
of ceiling tonight. When ceilings develop at klax...mostly expected to
remain in VFR category with 20 percent chance of brief MVFR
category. Still a 10 percent chance of showers overnight into
Saturday morning due to deep moist layer in place.
Kbur...moderate confidence in VFR ceilings remaining through evening
hours...then MVFR category overnight into Saturday morning. Still a
10 percent chance of showers tonight into Saturday morning due to
deep moist layer in place.
Outer waters...high confidence in small craft advisories for all
outer waters tonight through Saturday night. Early Saturday morning
winds will subside below criteria for a few hours...but will
increase later in the day. Sunday winds look to be slightly weaker
but there is a 30% chance the Small Craft Advisory will need to be extended.
Inner waters...there will be Small Craft Advisory winds for the
western portion of the Santa Barbara County tonight...with gusts 25
to 30 knots. Local Small Craft Advisory gusts will affect the western portion of
pzz655 this evening.
Small Craft Advisory (see laxmwwlox).