Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
425 am PDT Sat Oct 10 2015
***updated aviation section***
High pressure will gradually weaken this weekend and into early next
week. Afternoon temperatures will exhibit a gradual cooling
trend...although remaining above normal into early next week. An
approaching low pressure system will bring the possibility of
precipitation the middle of next week...with the best chances for
rain on Thursday.
Short term (today-mon)...overall...00z models in excellent synoptic
agreement through the period (which is a pleasant surprise given the
nature of the pattern). At upper levels...low will drift off the
Baja California Mexico coast today...and meander to about 640 miles southwest
of Los Angeles by Monday. Near the surface...weak diurnal gradient
trends will prevail (onshore during the day and offshore at night).
Forecast-wise...main issues will be temperatures and clouds. Latest
satellite shows mostly clear skies across the district...although a
sheet of stratus is working its way down the central coast. Do not
think this stratus will impact the central coast today. However for
tonight and again Sunday night...would not be surprised to see some
central coast stratus (which matches up well with the thinking of
the high res models). Otherwise...skies should remain mostly clear
through Sunday...but then turn partly cloudy on Monday as clouds
begin to rotate around the upper low.
As for temperatures...hot and dry conditions will continue through
Monday (although not as hot as friday). With upper ridge expected to
gradually weaken through the period and the diurnal gradient
trends...afternoon temperatures should exhibit a gradual cooling
trend (although remaining quite a bit above seasonal normals even by
monday). Of course if the marine layer were to become more
pronounced...temperatures near the coast would be cooler than
With weak offshore gradients and no upper level support...no issues
with any sort of offshore winds today.
Long term (tue-fri)...overall...models continue in good synoptic
agreement through Thursday...before diverging slightly. At upper
levels...low will begin to move northeastward on Monday...with the
low center passing near Point Conception on Thursday. On Friday the
GFS keeps moving the low/upper trough into the Great Basin while the
European model (ecmwf) keeps it lingering over California. Near the surface generally
weak onshore flow will continue.
Forecast-wise...this pattern will result in a continued cooling
trend for all areas...with Thursday likely the coolest day as
temperatures will be near normal. As for rain chances...both the GFS
and European model (ecmwf) indicate the potential for some shower activity. So...will
continue with chance/slight chance probability of precipitation Wednesday through Thursday.
On Friday...the system should be far enough east to limit any
precipitation possibilities. In terms of how much precipitation is
possible...the GFS is more bullish with rainfall than the European model (ecmwf).
However...too early to have even a shred of confidence in any
At 0800z...the marine inversion was surface based at klax. The top
of the inversion was 1900 feet with a temperature of 31 degrees
High confidence that all valley and inland taf sites will remain VFR
through the period. Moderate to high confidence that all coastal taf
sites will stay VFR through early this evening...with most sites
likely staying VFR for the entire forecast period. Ksbp and ksmx
will have the best chance for ceilings tonight...with LIFR conditions
possible to likely. Only about a 10% chance for other coastal sites
to have any ceiling or visby issues by Sunday morning.
Klax...high confidence in VFR conditions for the next 30 hours. Only
a 10% chance of MVFR visby or IFR/LIFR ceilings for Sunday morning.
Kbur...high confidence in VFR conditions for the next 24 hours.
Good confidence in the current forecast...with small craft
advisories in effect for pzz670 through late Sunday night and pzz673
through 9am this morning. Some local gusts to 25 knots will be possible
for western portions pzz673 this afternoon and this evening...but
likely not widespread enough for a Small Craft Advisory (sca). Small Craft Advisory
conditions could become more widespread across all outer waters late
Sunday afternoon and evening...so advisories may need to be re-
issued for pzz673 and pzz676 at a later time. Small Craft Advisory conditions are
unlikely for any of the inner water zones through the forecast
period. Dense fog will be possible for some zones through Sunday
morning...especially across the outer waters...and the nearshore
waters north of Point Conception.
Small Craft Advisory (see laxmwwlox).
Beach hazards statement (see laxcfwlox).