Area Forecast Discussion
Issued by NWS Los Angeles, CA

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168
FXUS66 KLOX 161150
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
350 AM PST Mon Jan 16 2017

.SYNOPSIS...
Offshore flow and mild weather will continue through the middle of
the week. Rain and mountain snow can be expected late in the week,
as a couple of low pressure systems approaching from the northwest
affect the region. Unsettled weather may continue through next
weekend.

&&

.SHORT TERM...(TDY-WED)

3 days of dry weather on tap before another rainy period.

A decent catalina eddy has spun low clouds up and into most of the
coasts and vly of LA and VTA counties. There is no inversion and
all of the low clouds are the result of low level moisture and the
lift of the eddy. The eddy is weakening and the low clouds should
clear out fairly quickly this morning. With the sunny afternoon
skies and 568 DM hgts max temps will reach close to normals this
afternoon.

A ridge and offshore flow builds into CA on Tuesday. Skies will be
clear. There will be some canyon breezes in the morning but
nothing near advisory levels. Just enough to ensure that there
will be no low clouds. Sunny skies...ridging and offshore flow
will make Tuesday the warmest day of the next 7 with max temps at
or a degree or two above normal.

On Wednesday the upper ridge will be pushed to the south as a very
cold gulf of Alaska low (510 DM) pushes towards the pac NW. There
will be a little eddy and some marine layer clouds across LA and
some of VTA county in the morning followed by increasing mid and
high level clouds moving in with the rapidly establishing quick
moving west flow. The increasing clouds...waning offshore flow and
lowering hgts will all combine to lower max temps 2 to 4 degrees.

.LONG TERM...(THU-SUN)

For the extended, 00Z and 06Z models are in pretty good synoptic
agreement and agree that unsettled weather will prevail through
the period.

The first storm will be a fast mover with a 80-90 kt jet pushing
perpendicular to the front. Rain will spread into SLO/SBA counties
early Wednesday evening and then into Ventura/Los Angeles counties
around midnight. The bulk of the rain will turn to showers of
SLO/SBA counties around dawn and then to VTA/LA counties by noon.
Scattered showers will continue through Thursday evening. Rainfall
totals with this storm should range from 0.25 and 0.75 inches with
locally higher amounts across the favored upslope areas (such as
Rocky Butte). Snow levels will start out above 8000 feet Wednesday
afternoon, but will drop to around 5000 feet by Thursday afternoon
with some light snow accumulations across the higher elevations.

A very fast moving pop up ridge will keep things dry Thursday
night.

A very powerful jet will bring a series of rapid fire storms to
the area through Monday. The second storm of the week will move
on through Friday and Friday night with scattered showers possible
through the day on Saturday. This system looks a bit more potent.
Initial rainfall estimates are for 0.50 to 1.50 inches (with
locally higher amounts in favored upslope areas). Due to the cold
origins of this storm snow levels will be lower (4000 and 5000
feet) Look for more snow to fall from this system.

The mdls begin to diverge for the last storm. It is not surprising
giving the incredible amount of jet energy associated with this
storm. the EC is faster than the GFS but both mdls indicate a
significant storm to affect the area from Sunday afternoon
through Monday afternoon. If the current mdl solutions are even
close to the truth this will be the most significant storm of
them all and by a fair margin. It will be interesting to watch the
forecast evolution of this system.

&&

.AVIATION...16/1200Z...

At 11Z at KLAX...there was no marine inversion, but there was a
moist layer to around 3500 feet.

VFR to locally MVFR cigs will affect much of the valleys and
coastal areas of VTU and L.A. Counties this morning, as well as
the interior vlys of SLO County. Weak offshore flow should cause
clouds to dissipate by mid to late morning. Then VFR conds are
expected everywhere this afternoon through Tue.

KLAX...Moderate confidence in the 12z TAF. There is a 20 to 30
percent chance that clearing will occur as early as 15z.

KBUR...Moderate confidence in the 12z TAF. There is a 20 to 30
percent chance that VFR cigs will drop to MVFR between 12z and
15z this morning.

&&

.MARINE...16/300 AM...

For the Outer Waters and inner waters north of Pt Conception...
moderate confidence in current forecast. Northwest winds will be
below SCA levels today through Wednesday afternoon. Southerly
winds are expected to increase Wednesday ahead of a frontal system,
likely reaching SCA levels Wed night, with SCA conds persisting
into the weekend as another front moves across the waters.

For the Inner Waters south of Pt Conception...light winds are
expected through Wednesday afternoon, then stronger winds
Wednesday night and early Thu, probably staying below SCA levels.
There is a better chance of SCA conds Friday,

A fairly large long period swell will affect the waters today
through Tuesday. A very large west swell is forecast to arrive
Friday night into Saturday...potentially reaching heights of 20
feet at 18 seconds over the northern outer waters late Friday
night.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through Tuesday evening for
      zones 40-41. (See LAXCFWLOX).
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK...(WED-SUN)
A wet and unsettled weather pattern is likely Wednesday night
through Monday. The heaviest rain during this period will probably
fall on Friday and again later Sunday and Monday. There is a chance
of damaging warning level surf and coastal flooding issues starting
Friday and continuing through Saturday, especially along the
Central Coast.

&&

$$

PUBLIC...Rorke
AVIATION...DB
MARINE...DB
SYNOPSIS...Sukup

weather.gov/losangeles



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