Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
1155 am PDT Thursday Jul 2 2015
..new aviation discussion...
Lingering monsoonal moisture will bring a threat of showers and
mountain and desert thunderstorms today...then just the mountains and
deserts on Friday. For the Holiday weekend...dry and slightly cooler
conditions are expected...with low clouds and fog making a return to
the coastal plain. For early next week...benign weather is expected
with seasonable temperatures and typical low clouds and fog
during the night and morning hours.
Short term (today-sat)...one last monsoon push this morning before
the moisture starts moving out of the area. Still not much in the
way of instability so anything we'll get this morning will just be
some sprinkles or light showers with almost no chance of measuring
01. Precipitable waters will be dropping through the day as the moisture scoots
out of the area to the north. But the increased sunshine by this
afternoon will allow better surface heating over the la/Ventura
mountains so there is a chance that we'll see some convective
development, but again outside of the surface heating and topography
there isn't a lot that the air mass is going to contribute to the
lift. Continued south flow will keep any convection out of the
coast/coastal valleys. Removed thunder from the morning forecast and
kept in for the mountains/av this afternoon/evening. Elsewhere,
decreasing clouds, especially southern areas. Slo/sba County may
hold on to mostly cloudy skies into later afternoon and evening
before the moisture moves through.
Soundings and profilers show cooler temperatures in the low levels today
and onshore gradients are stronger. So despite the increased
sunshine for southern areas temperatures today either similar to yesterday
or a few degrees cooler. Still fairly humid but a bit less than
yesterday, especially by this afternoon and evening.
Temperatures expected to trend slightly cooler each day through Saturday
with slightly stronger sea breezes and less humidity. Marine layer
expected to return tonight as the higher clouds depart and should be
here through the weekend, clearing to near the coast by middle to late
morning each day.
Models show just a little instability and low level moisture over the
la/Ventura mountains Friday and through the weekend, but precipitable waters much
lower, generally around a half inch. Will probably see some
afternoon cumulus each day but minimal chances for actual storms. If
nothing happens today will likely remove storms for tomorrow and
leave them out for the weekend.
***From previous discussion***
Long term (sun-wed)...for extended...models continue to exhibit
good synoptic agreement through the period. At upper levels...the
low offshore will gradually drift closer to the West Coast...and
will push the Great Basin ridge to the east. Near the surface...a
moderate onshore flow is forecast to continue.
Forecast-wise...a relatively unexciting forecast for the extended.
Marine layer stratus/fog should be the main story...pushing into the
coastal each night/morning...with a good dissipation each afternoon.
Otherwise...skies should remain mostly clear. As for temperatures
there will be minor day-to-day fluctuations due to the whims of the
marine layer...but should hover near seasonal normals.
At 1813z...the marine inversion at klax was based at 500 feet. The
top of the inversion was 2400 feet with a temperature of 23 degrees.
Moderate confidence in the 18z tafs. The transition from moist
monsoonal flow to a more typical Summer pattern will begin in the
next 24 hours. Expecting a return of marine clouds tonight with most
coastal sections seeing the clouds move in late tonight. The valley
sections should stay clear through Friday, but there is a slight
chance of marine clouds sneaking into kbur by early Friday morning.
In the mean time there is still an outside chance of an isolated
storm in the Antelope Valley this afternoon.
Klax...moderate confidence in the 18z taf. There is a 30 percent
chance of VFR conditions continuing through the night.
Kbur...moderate confidence in the 18z taf. There is a 30 percent
chance of marine clouds with IFR conditions sneaking into the
airfield by early Friday morning.
For now...the threat of Small Craft Advisory conditions is minimal through Saturday
..although there may be some local gusts to 25 knots near Point
The threat of thunderstorms has been removed from the forecast for
the remainder of today...but there could still be some isolated
sprinkles and showers.