Scientific Forecaster Discussion
fxus66 klox 241626
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
926 am PDT Wed may 24 2017
a low system will spread the night to morning clouds...fog and
possible precipitation farther inland...with below normal
temperatures into Saturday. A high will build in over the weekend
to push the marine layer back to the coast with temperatures to
warm to above normal by early next week.
High level moisture starting to arrive ahead of the upper low to
our southwest. Satellite imagery does show some vertical
development but at very high altitudes which matches up well with
the fairly steep hi lvl lapse rates in the vbg and nkx soundings
as well as in the models. However, lower level moisture is still
very much lacking, and now the models are showing some
stabilization this afternoon so this morning might be the best
chance if something were to happen. In any case, the decision to
keep thunderstorms out of the forecast still looks reasonable.
Marine lyr was around 1200 ft earlier this morning but has
deepened to close to 2000 ft currently and there were reports of
some light drizzle. It's possible the little waves embedded in the
flow aloft have assisted with the the marine lyr deepening and
drizzle. However, clearing is in progress and the clearing pattern
should take on a more traditional pattern today as opposed to
yesterday where it cleared earlier, made a brief return in the
late morning before clearing again. Highs today expected to be
10-15 degrees cooler for inland areas and 5-10 degrees cooler for
***From previous discussion***
Tonight the strong onshore push will combine with the falling hgts
and weak lift of the trof to raise the marine layer to between
4000 and 5000 feet. Clouds will push all the way to the coastal
slopes and deep into the vlys. Would not be surprised to see a
little drizzle near the foothills as well.
Hard to imagine any clearing on Thursday. The NAM forecasts an
afternoon onshore push of 11.2 mb which if true would be the
highest observed in the month of may since the turn of the
century. More than likely the gradient will be around 10 mb
onshore which is still strong enough to keep the clouds over the
area and advisory level gusts in the Antelope Vly. Max temps will
continue to fall esp in the vlys and the interior and most Max
temps will be 8 to 12 degrees blo normal.
Not much change on Friday and expect similar conditions to Thu.
The onshore push is forecast to be about 2 mb weaker than Thursday so
may just a little more clearing and maybe a degree or 2 of
The trof exits and a ridge builds in starting late Friday
afternoon. Just in time to Rescue the Holiday weekend. The ridge
will build every day and peak on Monday. The marine layer clouds will
not go away but it will be reduced in coverage a little each day
and will clear totally by late morning. Max temps will climb each
day. They will still be below normal on Saturday but will rise
above normal on Sunday and then on Monday Max temps should be 8 to
12 degrees above normal will more than a few 90 degree readings
likely in the vlys and deserts.
The ridge pushes off to the east on Tuesday and this will kick off
a slight cooling trend.
At 1000z, the marine inversion at klax was based around 1200 feet.
The top of the inversion was 2900 feet with a temperature of
24 degrees celsius.
Overall, moderate confidence in 12z taf package. Current IFR to
vlifr conditions at coastal sites will improve to VFR conditions
by the afternoon, although klax/ksmo/koxr will likely remain MVFR
through the afternoon. For tonight, high confidence in MVFR/IFR
conditions for all coastal and valley sites, but only moderate
confidence in timing (+/- 2 hours of forecast).
Klax...moderate confidence in 12z taf. Transition to MVFR cigs
will be between 16z and 20z. There is a 30% chance of VFR
conditions 20z-02z. For tonight, there is a 30% chance IFR cigs
Kbur...moderate confidence in 12z taf. There is a 20% chance of
IFR conditions 13z-16z. For tonight, high confidence in return of
stratus, but only moderate confidence in flight category (either
IFR or mvfr) and timing (+/- 2 hours of current 06z forecast).
For the outer waters, high confidence in current forecast. Winds
and seas will remain below Small Craft Advisory (sca) levels
through Friday. On Friday and Saturday, winds will likely increase
to Small Craft Advisory levels.
For the inner waters, high confidence in current forecast. For the
waters north of Point Sal, winds and seas will remain below Small Craft Advisory
levels through Friday, but will likely increase to Small Craft Advisory levels
Saturday and Sunday. For the waters south of Point Conception,
winds and seas will remain below Small Craft Advisory levels through Sunday.
California...Wind Advisory in effect from 2 PM this afternoon to 9 PM PDT
this evening for zone 59. (See laxnpwlox).
Hazard potential outlook...(fri-tue)
advisory level southwest winds are possible Friday across the
mountains and deserts.