Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
1045 am PST Thursday Jan 29 2015
..new aviation/marine discussions...
weak offshore flow will bring above normal temperatures today with
ample high clouds. A low pressure system to the south will bring the
possibility of light precipitation Los Angeles County later tonight
and Friday. Gusty offshore winds will occur this weekend...with high
pressure and above normal temperatures dominating the weather
pattern next week.
Short term (today-sat)...
overall forecast on track this morning...but updated forecast for a
few small details. Increased warming trend from yesterday over Los
Angeles and Ventura counties...as the offshore pressure gradients
are stronger. Cooled temperatures some on the central coast as the
offshore pressure gradients are weaker and temperatures are trending
lower than yesterday. Added dense fog to the interior slo valleys
for this morning.
***From previous discussion***
A trough will slowly move over the area today. It will bring plenty of
middle and upper level clouds to the area and skies will be mostly
cloudy. Every model keeps the rain to the south and east of the area
today so took out any mention of rain for today. Offshore flow is a
little stronger and there will be some morning canyon winds but
nothing advisory level. The bigger effect of the increased offshore
flow will be to boost maximum temperatures across the coasts and valleys by about
3 degrees from ydy.
Early Friday morning (late tonight - you choose) a weak upper low
will form in the base of the trough. This low will be to the south and
east of l.A. County and its flow pattern will bring a slight chance of
rain to l.A. County (mostly eastern la County especially the mtns) through late
Friday evening. If any rain falls rainfall amounts will be light. Of
note...the 06z runs are a little more bullish on the rain and if the
12z runs continue this trend may have to bump up probability of precipitation. The clouds
will be thicker and the offshore flow will be weaker and both these
will combine to knock a few degrees off of the maximum temperatures.
The upper low will push off to the south and east by dawn and skies
will clear out during the day Saturday. Heights will rise as a ridge
begins to nose into northern California. Offshore flow will increase again but
any canyon winds will be less than advisory levels. Maximum temperatures will
rise a few degrees.
Long term (sun-wed)...
a fairly large ridge will dominate the weather Sunday and Monday.
Offshore flow peaks Sunday morning and there might be some advisory
level wind gusts. Maximum temperatures will jump 3 or 4 degrees and maximum temperatures
will be 8 to 10 degrees above normal.
Monday will be very similar to Sunday. Just a little less winds and
a degree cooler.
The ridge relaxes just a touch Tuesday and there will be a few
degrees of cooling but maximum temperatures will still be above normal.
The ridge may build back in Wednesday for another warm up.
The GFS is still touting some rain way out in extended land but
where as the ec agreed with this idea last night...tonights run
keeps the rain to the north. But the nice thing about day 10
forecasts is that there is lots of time for change.
At 1737z...there is no inversion at klax.
VFR conditions will continue at most taf sites...except for kprb
where dense fog will make another late night visit. Good confidence
in the 18z forecasts.
Klax...VFR conditions are expected through Friday. There is a 20
percent chance of marine clouds tonight and light showers Friday.
Kbur...VFR conditions are expected through Friday. There is a 20
percent chance of light showers Friday.
Outer waters...Small Craft Advisory level winds from this
afternoon through early Saturday morning.
Inner waters...from between Ventura and Malibu...local NE winds 10
to 15 knots Sat night into Sunday morning. 50 percent chance for a
Small Craft Advisory for Sunday morning for this area.
Small Craft Advisory (see laxmwwlox).