Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
1013 am PST Sat Mar 8 2014
gusty offshore winds will continue for portions of Ventura and Los
Angeles counties through middle afternoon today...followed by weaker
offshore flow through Sunday. Well above normal temperatures will
continue through the weekend. Slightly cooler weather with
increasing clouds is expected early next week as a trough approaches
from the northwest. A warming trend is likely for the second half of
Update...mostly clear skies and warmer temperatures expected for
southwest California today. A few high clouds may affect the region
as upper level moisture continues to stream over the crest of a
ridge that is edging eastward from California into the Great Basin.
Offshore gradients across the area strengthened through 15z this
morning and are now beginning to back off slightly. The peak
gradient from lax to Daggett was -4.8 at 15z...with a peak of -9.9
for the lax to Tonopah gradient. The main weather concern today
continues to be moderate Santa Ana winds affecting all of Ventura
County and most of l.A. County today. The l.A. Coast will see
localized gusts to 35 miles per hour below passes and canyons of the Santa
Monica range...with gusts to 25 miles per hour in the San Gabriel Valley Hills.
A Wind Advisory is in effect for the mountains and western valleys
of l.A. County...and for Ventura County through 2 PM this afternoon.
While winds are expected to begin to diminish in the
afternoon...breezy conditions are likely to persist through the
evening across the higher ridges and the more exposed valley
foothill locations. Offshore winds will increase somewhat across the
mountains and valleys early Sunday morning...but should remain
below advisory level with gusts up to around 30 miles per hour.
Today's high temperatures will warm significantly in areas affected
by offshore flow...reaching the lower to middle 80s across the l.A. And
Ventura valleys and much of the coastal plain. Another unseasonably
warm day is expected Sunday as the weaker offshore flow continues.
However more high cloud cover will affect the areas north of Point
Conception as a trough approaches the Pacific northwest...pushing
the ridge south and east of the area.
From previous discussion...
Models have backed off on a more progressive and sharper shortwave
moving over northern California on Monday. All models continued to
keep a weakening cold front pushing through Monterey County to our
north. Although was tempted to rip out all probability of precipitation for the slo/sba
central coast...have tailed back probability of precipitation just to our border to match
with the Monterey National Weather Service office. Would not be surprised if probability of precipitation were
removed by the day shift. Have also taken out low clouds late Sunday
night/Monday morning for coast and valleys. There will be an
increase in high clouds to bring "partly cloudy" wording to the
forecast for Monday and there will be a brief cooling trend
beginning Tuesday...just not as much as previously thought.
Long term (tue-fri)...
both the GFS and European model (ecmwf) models are in decent agreement that a weak
upper low will push towards southern cal. Just enough to cause the
marine layer to deepen and with an eddy expected to
develop...chances are low clouds and patchy fog will develop across
the la/vtu coast and coastal valleys Monday night/Tue. Skies should
remain stratus free for the central coast as northerly winds should
keep skies stratus free to the north.
By Wednesday...another offshore gradient sets up which should allow for a
return of gusty NE winds and a warm up across the usual la/vtu
County coast and valley areas. One interesting feature that has
developed...a retrograding upper low will push westward towards
eastern cal on Wed/Thu. For now it should have very little effect on
the forecast as it remains well east of so cal. But...if future
models continue to track it closer it could cool temperatures further for
the interior and bring some upper support to the offshore winds
expected Wednesday. Winds will be decreasing on Thursday...but warm conds or
near normal conditions for this time of year should prevail into
Middle/upper level ridge of high pressure over the area will shift
east. Upper level strong north winds will become moderate north
after 09/06z and then moderate southwest after 09/21z while middle
level light to moderate northeast and east winds become light
northeast after 09/12z. Weak to moderate and mixed onshore and
offshore pressure gradient through 09/04z then weak to moderate
offshore gradient between 09/04-09/18z...becoming weak to moderate
onshore after 09/18z.
Klax...very likely current sky/visibility conditions will persist through
09/18z then ceilings 250. Chance winds 07014kt in a layer 006-020
Kbur...very likely current sky/visibility conditions will persist. Chance
winds 09012kt in a layer 015-020 by 09/13z.
Virtually certain - 95-100%
very likely - 80-95%
likely - 60-80%
chance - 30-60%
very unlikely - 20% or less
Wind Advisory (see laxnpwlox).
Small Craft Advisory (see laxmwwlox).
High rip current risk (see laxsrflox).