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Southwest California area forecast discussion 
National Weather Service Los Angeles/Oxnard California
615 PM PST Monday Mar 2 2015

..updated aviation discussion...

Synopsis...

There will continue to some isolated thunderstorms across the
forecast through tonight. Expect mountain snow down to near 4500
feet through early Tuesday morning. The remainder of the week will
have warm and dry conditions with daytime temperatures near or above
normal by Thursday.

&&

Short term (today-thu)...it has been another active day today in
respect to showers and isolated thunderstorms. There were reports of
pea size to 1/2" hail reported in many locations...but the biggest
unloading of hail occurred at Huntington Beach earlier this morning.
The Winter Weather Advisory for Los Angeles and Ventura counties
will be extended until 7 am Tuesday morning...while the same
advisory for the Santa Barbara County mountains will be allowed to
expire at 6 PM this evening.

Overall...the cutoff low that was situated over Southern California
yesterday has begun to fill in and pivot to the northeast towards
Nevada as another quick moving upper low rotates around the western
periphreal of the trough axis. This upper low has already become
cutoff and was located off the coast of Monterey. This new upper low
will continue to move south just west of Point Conception later this
afternoon. Then...continue to move just west of the so cal bight
later this evening and off the Baja California coast by Tuesday morning.

Have bumped up probability of precipitation for Los Angeles County to likely through the pre
dawn hours Tuesday. The upper low will be in a favorable location
for a diffluent pattern over la/oc counties which should help the
precipitation to continue into early Tuesday. Showers will continue to be
off and on...but a better organized band of showers should affect
much of Los Angeles County and eastern Ventura County late this
evening and a few hours past midnight. Snow will continue to fall
above 4500-5000 feet...especially for the eastern San Gabriel
Mountains through Tuesday. Rain totals will continue to vary widely
depending if thunderstorms continue to develop overnight. Some areas
might stay dry while some see an additional quarter inch...to near
an inch from a thunderstorm. Based on latest NAM-buffer soundings
along the Los Angeles coast...instabilities parameters still look
good. And low level shear will improve once again late this
evening...for the potential of a few rotating cells off the coast
which could produce a few waterspouts.

There will continue to be plenty of low level moisture lingering
into Tuesday. Therefore expect partly cloudy skies across the
region...with more sunshine by the afternoon. The mountains should
stay partly to mostly cloudy with a few showers and snow flurries
for the eastern San Gabriel Mountains and possibly the Grapevine.
High temperatures will be 3 to 5 degrees warmer in most locations Tuesday.

The trough axis will move east near The Four Corners region by
Wednesday while a 576 dm high sets uo over northern California
allowing for thickness levels to rebound over the area. The
combination of weak offshore flow and building high pressure...will
help temperatures to go up a few degrees on Wednesday...with more
significant warming on Thursday. Overall expect 5 to 10 degrees of
warming over those two days. Warmest valley locations will be in the
middle 70s by Thursday...and possibly the central coast.



Long term (fri-mon)...the warmer than normal temperatures will continue
through at least Saturday as high pressure will dominate the
forecast area. Highs will reach the lower 80s on Friday and Saturday.
By Sunday the ridge axis moves east as a deep upper trough begins to
push in across the area. There will be a very cold upper low several
hundred miles of the northern California coast but should keep a
trough axis over the forecast area bringing cooler temperatures to the
region by Sunday and this pattern will persist into Monday. There
could be some night through morning low clouds developing late in
the period.

&&

Aviation...03/0100z.

There was no marine inversion as of 00z.

This is a low confidence forecast. There will continue to be off
and on showers across the forecast area through this evening.
Showers could linger across Los Angeles County overnight. But expect
mostly MVFR/VFR conds

Klax...VFR to MVFR conditions through this evening followed by VFR
conditions late tonight and Tuesday. There is a 40 percent chance of
the timing of the end of precipitation will be more than two hours
plus or minus from the forecast.

Kbur...VFR to MVFR conditions through this evening followed by VFR
conditions late tonight and Tuesday. There is a 40 percent chance of
the timing of the end of precipitation will be more than two hours
plus or minus from the forecast.

&&

Marine...02/200 PM...

For the outer waters...high confidence in winds remaining below
Small Craft Advisory levels through tonight. On Tuesday and Tuesday
night...the northwest winds will increase with a chance of Small
Craft Advisory conditions developing. For Wednesday through the end
of the week...moderate confidence in winds remaining below Small
Craft Advisory levels.

For the inner waters...high confidence in winds remaining below
Small Craft Advisory levels through the week.

Through tonight...there will continue to be the threat of
thunderstorms. Any thunderstorms that develop will be capable of
producing brief heavy rain...small hail and possibly a waterspout.

&&

Lox watches/warnings/advisories...
Winter Weather Advisory (see laxwswlox).

&&

$$

Public...Kaplan
aviation/marine...ck
synopsis...kj

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