Scientific Forecaster Discussion
fxus66 klox 232016
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
116 PM PDT Tue may 23 2017
a low system will approach by midweek to spread the night to
morning marine layer farther inland. The temperatures will drop on
Wednesday and go below the seasonal normals from Thursday to
Saturday. A high will build in over the weekend to push the marine
layer back to the coast with temperatures to reach above the
seasonal normals by early next week.
A big southwest surge during the late morning hours pushed the
marine lyr and cool maritime air back to the beaches after briefly
clearing earlier in the morning. Temps also spiked unusually
early today as a result with some coastal areas reaching their
high for the day before 10am. The southwest push appears to be
weakening and shifting to a more traditional west northwest flow
and clouds are starting to break up so there could be a secondary
mid to late afternoon temperature spike.
Marine lyr expected to deepen tonight as we start to feel the
effects of a trough and the upper low to our southwest. Between
that and the increasing onshore flow highs Wednesday expected to
drop area-wide with the biggest drops from the valleys inland.
Also expecting to get at least near advisory level westerly winds
across the Antelope Valley by afternoon with the lax-dag gradient
close to 10mb. Keeping thunderstorms out of the forecast as
models still aren't showing enough moisture below 500 mb to
warrant much of a threat at this time, but still something to keep
an eye on as the instability is certainly there, especially across
the Ventura/sb mountains.
More significant marine lyr deepening expected Thu/Fri, up to
4000' or higher as the trough deepens across the west. Could see
some early morning drizzle either day, though a slightly better
chance Friday. Temps will drop further with most coast/valley
areas not getting out of the 60s. Skies will be very slow to
clear, if they do at all, and by Friday we could see a reverse
clearing trend. Continued breezy with advisory level winds likely
across the av.
Ridging over the weekend will bring a warming trend to all areas,
though highs will still be a few degrees below normal Saturday,
then warming to near to a few degrees above normal Sunday and
Monday. Marine lyr will shrink but still be around. Weak troughing
for Tuesday will begin a cooling trend.
At 1729z, at klax the marine layer was 800 feet deep. The top of
the inversion was 2200 feet with a temperature of 25 degrees
Low to moderate confidence in the 18z tafs. North of Point
Conception...the conditions will continue VFR except along the
immediate coast until the marine clouds move back inland this
evening with IFR conditions. South of Point Conception...taf
sites within 5 to 10 miles of the coast...such as
koxr...kcma...ksmo amd klax...are getting caught by a surge of
marine clouds into the immediate coastal sections. These four taf
sites have low confidence as any change in the surge of low clouds
will alter the forecast. The inland taf sites will remain VFR
until the marine clouds surge into the San Fernando Valley late
tonight with IFR conditions.
Klax...low confidence in the 18z taf. There is a 50 percent chance
of clearing skies this afternoon.
Kbur...moderate confidence in the 18z taf. There is a 20% chance
of VFR conditions through Wednesday morning.
For the outer waters, moderate confidence in current forecast.
Winds will diminish below Small Craft Advisory (sca) levels this
morning. Winds and seas are expected to remain below Small Craft Advisory levels
through Friday (although there is a 30% chance of Small Craft Advisory level winds
this afternoon and again Wednesday afternoon). By Saturday, there
is a good chance of winds increasing to Small Craft Advisory levels.
For the inner waters, high confidence in current forecast. Winds
and seas are expected to remain below Small Craft Advisory levels through Friday.
On Saturday, there is a good chance of winds increasing to Small Craft Advisory
levels in the afternoon/evening hours.
Hazard potential outlook...(fri-tue)
advisory level southwest winds are possible Friday across the
mountains and deserts.