Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
830 PM PST Monday Dec 9 2013
moderate to strong Santa Ana winds will persist into the early
morning hours on Tuesday for parts of the area...then begin to
subside. Hard freeze conditions are expected for many of the less
windy areas once again by early Tuesday morning. Temperatures will
return to near normal by middle week as weak offshore flow continues
and high pressure builds overhead...with above normal temperatures
expected by the weekend.
Short term (tonight-thu)...moderate to strong Santa winds continue
across portions of Los Angeles and Ventura counties this evening.
The strongest winds this evening are focused across the
mountains...especially the Santa Monica range. High wind warnings
remain in effect for the mountains tonight where there will continue
to be potentially damaging wind gusts. As of 7 PM...Malibu
Hills reported a wind gust of 71 miles per hour while Laguna Peak reported
a gust of 94 mph! Good upper level wind support...cold air
advection...and a strong surface 1044 mb high (centered over nevada)
came together to fuel this strong Santa Ana wind event. The strong
surface high generated strong offshore gradients across Southern
California. Current lax-Daggett gradient at -7.2 mb and peaked at
-8.1 mb earlier today. Wind advisories remain in effect
for most coastal and valley portions of Los Angeles and Ventura
counties...where gusts between 30 and 50 miles per hour have been common.
The gusty Santa Ana winds will continue to bring elevated fire danger
through Tuesday. For more details on the fire weather concerns...please
refer to the fire discussion below.
Today's Santa Ana event was a cold event driven by frigid air in the
Great Basin. Most wind prone valley areas remained in the 50s today
with some of the coastal areas barely climbing above 60 degrees.
Clear skies combined with the influx of very dry air will allow for
tremendous radiational cooling once again tonight across wind sheltered
areas. A freeze warning will again be in effect tonight for
the central coast...Santa Ynez Valley...sba South Coast...and Ojai
Valley. All of these areas will likely see hard freeze conditions
with temperatures falling into the 20s overnight into early Tuesday
morning. Meanwhile...temperatures will once again drop into the teens
across the Antelope Valley...Cuyama Valley...and interior valleys of
slo County (however 2 or more hard freezes have already occurred for
these locations). While the gusty offshore winds will keep temperatures
above freezing for many coastal and valley areas of Los Angeles and
Ventura counties...there will certainly be some wind sheltered valleys
that will be at risk for local sub-freezing temperatures.
Offshore winds will gradually diminish through the day on Tuesday.
Breezy offshore conditions will remain Wednesday into Thursday
as moderate offshore gradients linger. Gradual warming trend the
next few days with temperatures returning to normal levels by
*** From previous discussion ***
Long term (fri-mon)...warming trend to continue right on through
early next week as high pressure strengthens over the area and weak
to moderate offshore gradients continue. 12z European model (ecmwf) is even more
impressive with the warming than the GFS and we could be looking at
highs near 80 by Sunday or Monday for some coast and valley
High confidence in VFR conditions through period. Locations south
and east of Santa Barbara County will continue to see gusty
northeast winds with low level wind shear and turbulence.
Klax...high confidence in VFR conditions. Slight chance of low level
wind shear through this evening.
Kbur...high confidence in VFR conditions. A good chance of low
level wind shear.
Fire weather...elevated fire danger will continue through Tuesday due
to the gusty offshore winds and very low humidity. The greatest
concern is tonight when strongest winds will coincide with the
driest conditions to bring a brief period of critical fire weather
conditions. Wind gusts of 50 to 70 miles per hour have been common this evening
across the mountains of Los Angeles and Ventura counties while
coastal and valley areas have generally seen gusts in the 30 to 50
miles per hour range. Meanwhile an influx of very dry air has brought widespread
single digit humidities to Los Angeles and Ventura counties. In
fact...Leo carillo beach is currently reporting a 2% humidity at the
8 PM hour.
The offshore winds are expected to gradually diminish through the day
on Tuesday. However...there will still be several hours of single
digit humidities and some warming on Tuesday that will help to further
dry the fine dead fuels. As a result...elevated fire danger will
continue on Tuesday with brief critical fire weather conditions
gusty northeast winds will affect the inner waters through early
Tuesday. The strongest winds will be over the waters from Ventura
and southward to Santa Monica...extending westward to anacapa and
Santa Cruz islands. East to northeast winds with gusts of 25 to 30
knots are expected in this area as well as over the San Pedro
Channel out to Catalina Island...with the strongest winds occurring
late this afternoon and early this evening.
Small craft advisories remain in effect for the gusty winds and for
the choppy short period seas that will result from the winds.
Easterly winds waves of 3 to 5 feet are expected over the waters and
may also affect Avalon Harbor and Smugglers Cove at times through
early Tuesday. Hazardous conditions may be expected for boaters in
east facing harbors...and for improperly moored vessels exposed to
High Wind Warning (see laxnpwlox).
Freeze warning (see laxnpwlox).
Wind Advisory (see laxnpwlox).
Small Craft Advisory (see laxmwwlox).