Scientific Forecaster Discussion
fxus66 klox 240525
Area forecast discussion...updated
National Weather Service Los Angeles/Oxnard California
925 PM PST Thu Feb 23 2017
Dry and cool conditions will continue through Saturday. A couple
of weak weather systems are forecast to move into the area with a
chance of rain and mountain snow Saturday night through Monday
night. High pressure will bring clearing skies and gradually
warmer temperatures to the area Tuesday through Thursday.
Skies are clearing as a weak ridge of high pressure continues to
build into the California coast this evening. A northerly surface
pressure gradient remains across the state this evening, but the
gradient is starting to relax and breezy to locally windy
conditions will diminishing into Friday. Clear skies and drier air
mass in place will allow for wind-sheltered areas to cool to near
or below freezing late tonight and into Friday morning. Areas of
frost have been added to the interior portions of the area as well
as portion of the central coast, Ventura County valleys, the
western San Fernando Valley, and the interior slopes of the Santa
Monica Mountains. Frost advisories have been added to the package
for late tonight and early Friday morning with a freeze warning,
mainly issued for the Ojai Valley portion of the Ventura County
Otherwise, a warming trend will develop Friday with the ridge
*** From previous discussion ***
Some fairly significant model differences as we get into Saturday
night and Sunday with the next trough. Both the NAM and GFS show
the trough taking a more inland trajectory with usual northwest
low lvl flow. Some decent energy with the trough so for the
central coast still a very strong chance of rain Saturday night
into early Sunday, though pretty light. The problem is what
happens to that trough and cold front after it rounds pt
Conception and has to deal with downsloping winds off the
transverse ranges. The GFS solution is basically dry south and
east of sb for Sunday with just too much northwest flow and
subsidence. The 12z NAM was like this as well, though the 18z has
sort of trended back a little wetter. The European model (ecmwf) has been the most
consistent and shows at least some rain about a third of an inch
just about everywhere by noon Sunday. Still this is a far cry from
what the models had shown just a day or two ago. So this
ultimately might be a high pop but low qpf sort of event and
probably best not to make too many drastic changes at this time.
On Monday both the ec and GFS show another slug of moisture coming
through but with not much energy to work with. GFS is favoring
more of a southern trajectory to the moisture but ultimately it's
too soon to tell. Pops have been skewed higher in the south but
hard to rule out a shower anywhere. Either way, amounts again will
We should see fairly rapid drying/warming through the rest of the
week as offshore flow increases and a ridge builds in from the
west. If this pattern holds we could be looking at some 80s
returning to the area by the end of next week and possibly some
gusty Santa Ana winds at times.
At 00z, there was a deep mixed layer up to around 6000 feet at
VFR conditions will prevail throughout the forecast period. There
is a chance of moderate wind shear and turbulence through 08z at
terminals south of Point Conception.
Klax...high confidence in VFR conditions throughout the period.
North cross winds should redevelop between 02z and 05z. Winds
will likely exceed 10 knots through 07z but should remain below 20
knots. Any northeast winds should remain less than 7 knots. There
is a 20 percent chance of moderate wind shear and turbulence
through 08z at terminals south of Point Conception.
Kbur...high confidence in VFR conditions throughout the period.
There is a 30 percent chance of moderate wind shear and turbulence
Gusty northwest to north winds along with short-period steep seas
will linger into early Friday morning for most areas, possibly
lingering into Friday night across the southern outer waters.
There is a chance of Small Craft Advisory level winds across the
southern waters, including the inner waters south of Point
Conception again on Saturday night and into Sunday night with a
trough approaching the area.
California...frost advisory in effect from 2 am to 9 am PST Friday for
zones 34-35-45-46-547. (See laxnpwlox).
High surf advisory in effect until 8 am PST Friday for zones
40-41-87. (See laxcfwlox).
Freeze warning in effect from 2 am to 9 am PST Friday for
zone 44. (See laxnpwlox).
Pz...Small Craft Advisory in effect until 3 am PST Friday for
zones 645-650-655-670. (See laxmwwlox).
Small Craft Advisory in effect until 9 am PST Friday for
zones 673-676. (See laxmwwlox).
Hazard potential outlook...(sun-thu)
no significant hazards expected.