Scientific Forecaster Discussion
fxus66 klox 111249
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
449 am PST Wed Dec 11 2019
Temperatures will trend warmer into Friday despite some periods
of clouds as high pressure shifts off to the east. A large
westerly swell is expected to arrive Thursday, bringing high waves
to most coastal regions through the weekend. Additionally, locally
gusty northerly winds will develop tonight and last into the
Short term (tdy-fri)...11/358 am.
Lots of high clouds streaming across the region this morning,
especially across northern sections as the southern end of a
weakening front grazes areas north of pt Conception. Expect any
rain to remain well to the north of the forecast area this
morning. Some low clouds have developed on the central coast and
in the Santa Ynez and Salinas valleys, but they were patchy in
nature, likely disrupted by the high cloud field. South of Point
Conception, some stratus was trying to develop just off the coast
of l.A, County, and patchy low clouds could push onshore for a
few hours this morning. Any low clouds should be gone by mid or
late morning, but there should be enough high cloudiness to
warrant partly cloudy wording for the forecast for today.
After the weak front passes to the north, weak ridging will build
into the region, and heights and thicknesses will rise a bit, as
will temps at 950 mb. This should lead to a couple of degrees of
warming in most areas today, with temps not far from normal for
mid December in most areas. North-SW gradients will increase across
the region later today into tonight. Expect some gusty winds thru
and below passes and canyons of the Santa Ynez range and across
the adjacent South Coast of sba County, but expect winds to be
just below advisory levels in most areas this evening. Gusty winds
will likely also affect the Interstate 5 corridor, but will likely
also be below advisory levels.
An upper ridge will build into the region from the southwest on
Thu and persist through Fri. Expect for some occasional high
clouds across the region, skies should be mostly clear Thu through
Fri. Expect some warming in most areas on Thu, with a bit more
warming likely on Fri.
North-S gradients will increase each day, so expect gusty northwest
to north winds thru and below passes of the Santa Ynez range and
on the South Coast of sba County, probably reaching advisory
levels Thu night and Fri night, with the strongest winds likely
Fri night. Advisory level northwest winds are also likely across
the Interstate 5 corridor at times late Thu through Fri night.
Long term (sat-tue)...11/446 am.
The ridge across the region will flatten out on Saturday as a
trough moves into the Pacific northwest and northern California. This system will
drop quickly into Nevada Sat night. Its track will not be favorable
for producing widespread rain across the region, but could bring
some showers to interior sections of slo and sba County and the
northern mountains of vtu and northwestern l.A. Counties Sat,
especially in the afternoon, into Sat night, with some showers
possibly lingering into sun. There will be significant cooling
across the entire region on Sat, with temps dropping back to
several degrees below normal levels. Snow levels should drop below
5000 feet Sat night, and there is a chance that snow could cause
problems on portions of Interstate 5 late Sat night/Sun morning.
North-S gradients will remain rather strong Sat night through Sun
night, so expect gusty advisory level winds across southern sba
County and through the Interstate 5 corridor. Max temps on Sunday
will likely be a bit lower than on Sat, especially in the
mountains and deserts.
The trough will move into The Rockies sun and into the Central
Plains on Mon, as a ridge will begin to build across the eastern
Pacific. Expect clear skies, with some warming in most areas on
Monday, with temps back up to close to normal levels,
Operational models are showing some differences to Tue. The ec
shows an amplifying ridge right across the region, with offshore
flow. This would result in dry and warmer weather across the
region for Tue. The 00z run of the GFS showed an upper low moving
into the West Coast, bringing rain to northern areas during the
afternoon Tue, but the 06z run is quite a bit slower, keeping some
ridging in place. GFS ensembles mostly keep rain out of the
central coast until after 00z on the 18th, so the slower solution
shown by the 06z operational GFS may be the way to go. With Tue
being a warmer drier day than currently forecast.
At 1030z at klax... there was a surface based inversion up to
around 1200 feet with a temperature of about 14 degrees celsius.
Overall... moderate to high confidence in the current tafs. Periodic
vlifr/LIFR conditions at ksmx and klgb through 1730z and IFR/MVFR
conditions at kprb and klax through 17z. There is a sixty percent
chance of LIFR/IFR conditions returning to klgb after 06z and
IFR/MVFR conditions returning to kprb, ksbp, and ksmx after 08z.
Otherwise and elsewhere VFR conditions will prevail.
Klax... moderate confidence in the current taf. There is a twenty
percent chance of occasional MVFR cigs through 15z. Otherwise VFR
conditions will prevail. There is a less than ten percent chance
of east winds greater than 8 kts through 17z and a ten percent
chance after 12/10z.
Kbur.... moderate confidence in the current taf. VFR conditions
will prevail throughout the forecast period.
Patchy dense fog with low visibility is possible anywhere in the
coastal waters today.
Conditions will remain generally mild through Wednesday morning
then Small Craft Advisory (sca) conditions develop Wednesday
afternoon and continue into the weekend. Winds will be elevated
from the central coast to San Nicolas Island and will also affect
portions of the Santa Barbara Channel and Santa Monica basin at
times. Short period choppy seas will become more prevalent
everywhere during this event.
A large and long period west to northwest swell will impact the coastal
waters Thursday through Saturday, resulting in hazardous sea
conditions and large breaking waves near shore. Breaking waves at
the Morro Bay and Ventura Harbor entrances are possible.
A large long-period west to northwest swell will push on to the
coast of central and Southern California Thursday night, peak on
Friday, then slowly diminish over the weekend. Swells off the
central coast will likely peak between 12 and 16 feet. Over the
southern waters, the peak will likely be between 6 and 10 feet.
High surf advisories will likely be needed over all beaches during
the peak, with strong rip currents and dangerous breaking waves
developing as well.
High tides will be around 6.5 feet Friday and Saturday mornings
and minor coastal flooding is possible during this time. Any
coastal flooding impacts should be confined to the beaches and to
nearby bike paths, walkways, and the most vulnerable parking
lots. There is a small chance of more impactful flooding over
vulnerable roads in the Ventura area.
California...beach hazards statement in effect from Thursday morning
through Monday morning for zones 34-35. (See laxcfwlox).
Beach hazards statement in effect from Thursday evening
through Sunday morning for zones 39>41-87. (See laxcfwlox).
Pz...Small Craft Advisory in effect from 3 PM this afternoon to 3
am PST Thursday for zone 650. (See laxmwwlox).
Small Craft Advisory in effect from 3 PM this afternoon to 3
PM PST Saturday for zones 673-676. (See laxmwwlox).
Hazard potential outlook (fri-tue).
High surf is likely and minor coastal flooding is possible for
late this week at area beaches. Strong north winds possible
Sunday in southern Santa Barbara County, and parts of la/Ventura