Area Forecast Discussion
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FXUS66 KLOX 101813
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1013 AM PST Sat Dec 10 2016
Updated Aviation Discussion
A chance of light rain will continue through Sunday morning, with
the best chance of rain on the Central Coast. Dry weather is
expected Sunday afternoon and Monday. Rain could return to the
Central Coast by Tuesday, then possibly the entire area late next
week as a stronger low pressure system develops. Near or slightly
below normal temperatures are expected through next week.
Low clouds and fog with patchy dense fog was noted over the coast
and vlys of swrn CA this morning. These low clouds are forecast to
gradually dissipate thru the morning hours. Otherwise, partly to
mostly cloudy skies will prevail across the forecast area thru the
afternoon as some moisture at lower to mid levels continues to
stream in from the w. A slight chance to chance of showers can also
be expected over SLO/SBA Counties thru the day, altho the best
chance of showers will be toward the Monterey County border. Some
gusty nw winds can be expected over higher terrain and in the
Antelope Valley today as well. Temps across the region are expected
to be several degrees below normal for the coast and vlys, and
several degrees above normal for the mtns and deserts. Highs should
reach only into the mid to upper 60s in the warmest vlys and coastal
areas this afternoon.
A flat upper level ridge will linger over srn CA today. A weak
impulse will lower 500 mb heights tonight from around 580 dm to 575
dm or so, with little change expected Sun thru Mon as a broad wnw
flow aloft persists.
A weak surface cold front is forecast to sag south from central CA
into SLO/SBA Counties tonight then dissipate as it moves further s
on Sun. This front will bring cloudiness and widespread light rain
to SLO/SBA Counties tonight then taper off to scattered showers by
Sun morning. There will also be a chance of rain mainly on the n mtn
slopes of VTU/L.A. Counties during the period. This front will be
accompanied with nw flow thru the lower levels which should limit
the rain from moving s of the mtns over VTU/L.A. Counties, altho
there should still be a slight chance of pcpn for the coast and vlys
later tonight into Sun morning.
Rainfall will be light over the region tonight thru Sun morning,
with about 0.05 to 0.15 inch expected for SLO/SBA Counties and the n
mtn slopes of VTU/L.A. Counties, except up to 0.25 inch cannot be
ruled out in far nwrn SLO County. Elsewhere over VTU/L.A. Counties,
0.05 inch or less can be expected, with many locations probably not
receiving any pcpn at all.
Lingering moisture at mid and upper levels will continue to move in
from the w Sun afternoon thru Mon which should keep partly cloudy
skies as a whole over the area. However, the 12Z NAM was indicating
plenty of moisture below 2000 ft with a weak eddy Sun night into Mon
morning s of Point Conception, with low clouds and fog possible for
the coast and vlys of VTU/L.A. Counties.
Temps on Sun are forecast to remain several degrees below normal for
the coast and vlys and a few degrees above normal for the mtns and
Antelope Vly. Temps should warm slightly overall on Mon, with highs
near normal to slightly below normal for the coast and vlys, and 4
to 8 deg above normal in the mtns and deserts. Highs in the warmest
vlys and coastal areas should reach the mid to upper 60s on Sun,
and mid 60s to around 70 for Mon.
***FROM PREVIOUS DISCUSSION***
Overall, 00Z models continue to exhibit decent synoptic agreement
through the period. At upper levels, near zonal flow will continue
through Wednesday, then a trough will move across the area
Thursday and Friday. Near the surface, weak onshore flow will
prevail through Wednesday with stronger flow developing on
Thursday and Friday.
Forecast-wise, Tuesday and Wednesday will be partly to mostly
cloudy days. There will br the threat of some light rain north of
Point Conception as the tail end of a northern California system
clips the area. Rainfall amounts, if any, will be light. On
Thursday and Friday, a more significant system is forecast to
impact the area. The models exhibit some differences in timing
(ECMWF faster than GFS), but there is a good chance of decent
rainfall sometime Thursday through Friday.
At 11Z at KLAX, the marine layer was 1700 ft deep (base temp of
11C) with an inversion to 5000 feet (temp of 15C).
Moderate confidence of 015-25 CIGS common 20-03Z at most coastal
airports (except KSBA)...with high clouds VFR elsewhere. Moderate
confidence of CIGS 005-015 common at all airports (except KPMD
KWJF) after 06Z tonight. Low confidence on timing of CIG arrivals.
High confidence of periods of -RA/RA after 00Z at KPRB KSBP KSMX,
with a 30 percent chance of occasional LIFR. 30 percent chance of
occasional -RA and briefly lowered CIG/VIS elsewhere after 03Z.
Periods of -DZ more likely.
KLAX...60 percent chance of occasional SCT decks 20-02Z, but low
confidence in timing. Moderate confidence in CIGS around 012
arriving by 02-05Z tonight, with a 30 percent chance for CIGS
under 010 after 06Z. 30 percent chance of -RA/-DZ after 09Z.
KBUR...Moderate confidence in VFR conditions and high clouds
through 03Z. Moderate confidence in CIGS around 008 arriving by
02-06Z tonight, with a 30 percent chance for CIGS under 005 after
06Z. 30 percent chance of -RA/-DZ after 09Z.
Moderate to high confidence that gusty w to nw winds (around 25
KT) and/or short period steep seas (4-6 feet at 6-8 seconds) will
reach the lower end of Small Craft Advisory (SCA) levels across
the southern two thirds of the outer waters, and at least western
portions of the southern inner waters (Santa Barbara Channel and
Santa Monica Basin) later today through tonight.
Winds should decrease some late tonight, but SCA NW winds are
likely across the outer waters Sunday afternoon and night. Winds
could get close to advisory levels nearshore on the Central Coast
as well, and over the western portions of the SBA channel. Choppy
short-period seas will likely continue everywhere through at
least Monday, but should be smaller than tonight.
PZ...Small Craft Advisory in effect until 3 AM PST Sunday for
zones 650-676. (See LAXMWWLOX).
Small Craft Advisory in effect from 3 PM this afternoon to 3
AM PST Sunday for zones 655-673. (See LAXMWWLOX).
.HAZARD POTENTIAL OUTLOOK...(MON-FRI)
There is the potential for widespread rains and gusty winds later
next week. Still considerable uncertainty in timing and amounts
from this storm, but most likely impacting the area sometime
between Thursday and Friday. There is the potential for a cold and
unsettled pattern lingering into next weekend, with a threat of
rain showers and mountain snow.