Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
1003 am PST Thursday Feb 11 2016
The high system will bring another day of record temperatures on
Thursday...with above normal temperatures into early next week. A
low system will arrive by the middle of next week for possible
precipitation and a cooling trend.
A potent upper level ridge with weak to moderate offshore
surface pressure gradients will remain the story as it has been
this week...with several temperature records threatened.
Conditions will feel very similar to yesterday...though high
temperatures could be down a few degrees closest to the coast as a
healthier afternoon seabreeze is expected compared to
yesterday...especially on the central coast. Clear skies will
continue...though a few high clouds will smatter the horizon over
slo and sba counties. Forecast is in good shape...with a very
minor update to temperatures.
***From previous discussion***
The upper ridge will continue to breakdown on Friday with a few
high clouds across the forecast area. With heights and thickness
levels lowering a bit...look for a few more degrees of
cooling...especially for coastal areas. The morning offshore flow
will be very weak before turning weakly onshore Friday afternoon.
Highs will remain in the lower to middle 80s for la/vtu coast and
valleys...with cooler conditions to the north.
On Saturday a weak upper disturbance will move through the area.
The onshore flow associated with this passing dry system will
cause temperatures to continue to trend down with onshore winds through
the day. Highs will generally remain in the 70s for areas north of
point Santa Barbara...with highs ranging from the middle 70s to
lower 80s for l.A./Vtu counties. As the trough pushes
through...gusty northerly winds are expected to develop across the
sba County mountains and adjacent South Coast...as well as the I-5
corridor and wind prone areas from Santa Clarita to the San
Fernando Valley into the Santa Monica Mountains. Wind advisories
might be needed for the mountains and possible the sba South Coast
Made some changes to the long term forecast. In the wake of the
exiting trough...a weak upper ridge will develop and stick around
through Tuesday. At the surface...latest 00z-06z NAM WRF was now
shifting the northerly winds Saturday night to northeast by Sunday
morning. Therefore what was once showing some cooling Sunday will
now warm up quickly on Sunday due to the offshore Santa Ana winds.
Winds will be light at best for the Marathon runners...but temperatures
will climb quickly Sunday morning into the early afternoon. The
GFS keeps the surface gradients northerly until Sunday evening before
shifting NE on Sunday night...but the higher resolution NAM
usually does a better job indicating the wind shift due to the
surface high placement over the Great Basin.
For Sunday then...high temperatures should Jump Up 4-7 degrees into the
middle 80s across the l.A/vtu coast and coastal valleys Sunday
morning. The offshore winds which are not expected to be
strong...but could be locally moderate in the usual wind prone
areas will persist through at least Tuesday morning with high
temperatures likely to remain in the 80s.
Both the GFS and European model (ecmwf) are in good agreement advertising a weak
cut off low placed several hundred miles west of Baja California. Another
upper trough will dig south approaching southern and central
California by Wednesday enveloping the cutoff low. A frontal
boundary with rain will move into the forecast area sometime
between Wednesday and Thursday. There were the usual timing
differences with the arrival...but models have been consistent
over the last couple of days showing this. At this time rainfall
totals look anemic...but its still early. There will be
significant cooling on Wednesday and Thursday next week.
Middle/upper level ridge of high pressure over the area and trough of
low pressure upstream will persist. Upper level light to moderate
southwest winds and middle level light and variable winds will
prevail over the area. Mixed weak onshore and offshore pressure
gradient through 11/03z and weak offshore gradient between
11/03-11/19z and mixed weak onshore and northerly gradient after
Marine layer at lax at 1600z is none.
Klax...current sky/visibility conditions will likely persist through the
Kbur...current sky/visibility conditions will very likely persist
through the period.
Virtually certain - 95-100%
very likely - 80-95%
likely - 60-80%
chance - 30-60%
very unlikely - 20% or less
Northwest winds will increase and Small Craft Advisory conditions
are likely from Piedras Blancas to Point Sal 10-60 nm and from
Point Sal to Santa Barbara Island each afternoon Friday through
Sunday. There is a chance the conditions will develop earlier and
tonight. Small Craft Advisory for hazardous sea conditions with
swells building over 10 feet is likely from Piedras Blancas to San
Clemente Island excluding the inner basins south of Point
Conception tonight and persists through Sunday. There is a chance
swells will build to near 10 feet in the Santa Barbara basin
California...high surf advisory in effect from 3 am Friday to 9 am PST
Sunday for zones 34-35. (See laxcfwlox).
Beach hazards statement in effect from Friday morning through
Sunday morning for zone 39. (See laxcfwlox).
High surf advisory in effect from 9 am Friday to noon PST
Sunday for zones 40-41-87. (See laxcfwlox).
Pz...Small Craft Advisory for hazardous seas in effect from 3 am
Friday to 3 PM PST Sunday for zone 645. (See laxmwwlox).
Small Craft Advisory in effect from 9 PM this evening to 3 PM
PST Sunday for zones 670-673-676. (See laxmwwlox).