Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/06/16
AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
831 PM PDT MON SEP 5 2016
Temperatures will warm to near normal by Wednesday as a trough of
low pressure exits the region and onshore flow weakens.
Temperatures will fall below normal for the end of the week
through the weekend as onshore flow increases again. Night
through morning low clouds and fog will continue to affect some
coastal and valley areas.
Overall, a quiet evening across the district. Overnight, the only
issue will be the development of the marine layer stratus. For
areas north of Point Conception, sounding data indicate marine
inversion based around 1400 feet. With weak onshore gradients
prevailing through the night, stratus/fog should develop along
the Central Coast with the best coverage across the west coast
of Santa Barbara county. For areas south of Point Conception, the
stratus forecast is much more tricky and confidence in what
exactly will happen is low. Onshore flow is currently weaker
than last evening and the latest AMDAR soundings across the LAX
basin indicate several weak inversions in the lower atmosphere.
So, stratus/fog should develop, but amount of areal coverage will
be questionable. Current forecast has stratus/fog pushing into
the coastal valleys and up to the south coast of Santa Barbara
county. Will keep with this forecast thinking for the evening
update, but would not be surprised to see the stratus coverage
be noticeably less than current forecast.
Otherwise, no issues with winds or temperature forecasts tonight
and Tuesday. No significant changes are planned for the forecast
at this time.
Trough slowly exiting the area to the east tonight and early
Tuesday with rising heights behind it through Wednesday. The
warmer air mass combined with weaker onshore flow will lead to a
shallower marine lyr, earlier clearing, and warmer daytime highs.
Interior areas will see the biggest jumps next couple days with
Antelope Valley and interior SLO valleys breaking into the 90s as
early as tomorrow and the coastal valleys by Wednesday. Gradients
trend about a millibar offshore each of the next couple days, but
by Wednesday afternoon a good onshore trend develops as the ridge
weakens. Still, most areas will see their warmest day of the week
on Wednesday. Coastal temp forecasts were trimmed back a couple
degrees because of that afternoon onshore trend and most of the
model guidance and local historical studies favoring slightly less
warmup near the coast.
Heights don`t change too much Thursday, but strong onshore trends
will bring cooling to most areas except the very far interior.
Moisture from Newton expected to remain well east of our area and
not expected to have any role in our local weather.
After the cooling Thu very little change is expected through the
weekend. Both the GFS and ECMWF show a little vort max spinning up
off the coast of northern Baja Thursday, unrelated to Newton, and
moving north into the coastal waters off San Diego late Friday
into early Saturday. So far models show absolutely zero moisture
associated with this feature so right now there is no concern for
any convective development. But something to keep an eye on.
Otherwise, looks like a very quiet weather weekend in southern
California with temps within 5 degrees of normal in most areas and
just typical night/morning low clouds and fog for coastal areas.
On Monday a trough moving into the Pac NW will lower heights
further and cool daytime highs a few degrees area-wide. Still not
seeing any threat for monsoon convection the next 10 days at
least, maintaining our basically absent monsoon season so far.
At 2300Z, the marine inversion at KLAX was based near 2500 feet.
The top of the inversion was 5200 feet with a temperature of 16
Overall, low confidence in 00Z TAF package. Current sounding data
indicates marine inversion is very weak which leads to very
limited confidence in the extent of stratus development tonight,
especially south of Point Conception. Will continue with previous
thinking of MVFR/IFR ceilings developing overnight at all coastal
and valley TAF sites except for KSBP and KPRB. However, confidence
in timing of stratus arrival, let alone confidence in stratus
development, is low.
KLAX...overall, low confidence in 00Z TAF. High confidence in VFR
conditions prevailing through this evening. However confidences
wanes considerably tonight as there is a 50% chance that MVFR
ceilings will not develop at all. If MVFR ceilings do develop,
confidence in timing is also low.
KBUR...overall, low confidence in 00Z TAF. High confidence in VFR
conditions through this evening. Overnight, there is a 50% chance
that MVFR ceiling restrictions may not develop. If ceiling
restrictions do develop, confidence in flight category and timing
For the Outer Waters, high confidence in current forecast.
Northwest winds will remain at Small Craft Advisory levels
through tonight for all three zones (670/673/676) and into
Tuesday night for 670/673. By Wednesday and continuing through
the end of the week, winds and seas are expected to remain
below Small Craft Advisory levels.
For the Inner Waters, high confidence in current forecast. For
the week, winds and seas are expected to remain below Small
Craft Advisory levels.
PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday For
zones 670-673. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 AM PDT Tuesday For
zone 676. (See LAXMWWLOX).