Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
521 am PDT Wednesday Aug 31 2016
Temperatures will remain above normal today. Low pressure will
then dominate the weather for the rest of the period. The onshore
flow will increase the overnight marine layer and cool temps to
Marine layer clouds behaving about as expected and are across srn
la couonty and wrn sba County. The marine layer is about 1300 feet
deep which is deep enough to allow a few clouds into the San
Gabriel Vly as well. There was a pretty good sundower last night
but the winds have subsided nicely and the advisory expired at 300
am. There will be another sundowner tonight but it will be weaker
than last nights. The ridge will push off to the east today and a
trof will move into West Coast. The lower hgts will cool things
off some across the inland and slight onshore trends will cool the
coasts and vlys...still the cooling will be slight and all areas
save the beaches will have above normal temps with some triple
digit heat remaining in the warmest Vly spots. Another round of NE
sfc morning winds across the slo County coast so look for another
burst of morning heat followed by afternoon cooling there. Still
Max temps will likely only reach into the upper 80s rather than
the lower 90s as it happend ydy morning.
A little more trofing Thursday will translate into a little more
marine layer (ventura should see some low clouds) and continued
cooling. Still most areas will be several degree above normal.
By Friday the trof axis will be through the state and there will
be enough lift to push the marine layer stratus across most of the
coasts (north flow will keep the sba S CST clear) and some of the
vlys. Hgts fall to 585 dm and with a deeper marine layer and
better onshore flow will prompt a big cool down with most areas
falling to below normal.
GFS and ec are in agreement that the West Coast trof will persist
and even strengthen over the weekend look for a deeper and deeper
marine layer with night through morning stratus covering all of
the coasts and most if not all of the vlys. Max temps will fall
each day and Sunday is forecast to be the coolest with Max temps
10 to 15 degrees blo normal across the vlys.
Hgts rise a little on Monday and then some more on Tuesday. There
will be a degree or two of warming across areas away from the
coasts and then a more substantial warm up on Tuesday. Still Max
temps will be several degrees blo normal.
At 1130z, the marine layer depth at klax was 1500 feet. The top
of the inversion was near 3000 feet with a temperature of 30c.
Low clouds were affecting coastal sections of l.A. County, portions
of the San Gabriel Vly, srn portions of the central coast and the
Santa Ynez Vly. Conds were mostly IFR to LIFR. There is a slight
chance that IFR cigs will push into portions of the vtu County
coast and the S coast of sba County for a couple of hours this
morning. Skies are expected to clear in most areas by mid morning.
Expect similar low cloud pattern tonight/Thu morning, with cigs
mainly across l.A. County coastal areas and the central coast.
There may be another sundowner across srn sba County this evening
with some low level wind shear and MDT uddf.
Klax...moderate confidence in the 12z taf. There is a 20 to 30
percent chance that IFR cigs will dissipate as early as 15z.
There is a 20 percent chance that cigs will arrive as early as 06z
Kbur...high confidence in the 12z taf with VFR conditions through
Rather high confidence that gale force winds will continue across
the outer waters through at least late tonight and possibly
through Thu night.
There is a 30 percent chance the Small Craft Advisory level winds will occur across
the northern inner waters late this afternoon through this
evening, and across portions of the sba channel this evening.
For southern Santa Barbara County (the Santa Ynez range and South
Coast of Santa Barbara county), red flag warning will remain in
effect through Wednesday morning. Sundowner winds gusting between
40 and 50 mph will continue tonight through and below passes and
canyons. The strongest winds are expected to occur from in the
hills from San Marcos Pass to Gaviota, as well as the hills above
Montecito. Current Santa Barbara-Santa Maria gradient as of 8 PM
is -4.8 mb, which is similar to yesterday evening at this time.
Above the shallow marine inversion, relative humidity in the teens
will continue through the evening hours. Additionally, relative
humidity will exhibit poor recovery tonight. With this combination
of gusty winds and low relative humidity, an extended period of
critical fire weather conditions is expected across southern Santa
Elsewhere across the area, hot and dry conditions are
expected to continue through Wednesday. Afternoon temperatures
will show a slow cooling trend, but remain well above normal. So
with relative humidity expected to drop into the teens again
Wednesday afternoon, elevated fire weather conditions can be
expected across interior sections. The warm temperatures near the
surface will cause steepening lapse rates that will enable deep
vertical mixing layers through Wednesday when mixing layer heights
are forecast to range between 12,000 and 15,000 feet. For existing
fires or new ignitions over interior areas, plume dominated fire
behavior will be possible.
California...red flag warning in effect until 10 am PDT this morning for
zones 239-252. (See laxrfwlox).
Pz...Gale Warning in effect until 3 am PDT Thursday for zones
670-673-676. (See laxmwwlox).