Area Forecast Discussion
Issued by NWS Los Angeles, CA

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464
FXUS66 KLOX 012140
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
240 PM PDT SUN MAY 1 2016

.SYNOPSIS...
A departing low pressure system will bring the slight chance of
showers and thunderstorms through this evening across interior
areas. A gradual warming trend is expected through Tuesday as
high pressure aloft briefly builds into the region. A slow moving
low pressure system may bring showers and thunderstorms with
cooler conditions to the area Thursday through the weekend.

&&

.SHORT TERM...(TDY-WED)

Main short term impact is potential convective showers and thunderstorms
across interior sections of forecast area this afternoon and
evening. As of 2 pm, satellite imagery showing considerable
cumulus/towering cumulus clouds developing across interior
sections, mostly over the mountains. Doppler radar showing
a few storms producing rain showers over our local mountains
and interior valleys of SLO county, with only lightning strikes
so far being observed to our north in Kern county.

Weak upper level low pressure system centered over Central
California will bring some cyclonic flow and associated vort
energy across our forecast area this afternoon. Some residual
moisture across the region this afternoon, with precipitable
water values ranging between .7-.8 inches. With ample early May
sunshine and still some cold air aloft (500 mb temperatures as low
as -18 degrees celsius across interior sections), there will
likely be enough instability and moisture to continue generating
some showers over the mountains, deserts, and interior valleys
this afternoon and early evening. With latest NAM model soundings
showing lifted index values ranging between -2 and -4, and surface
based CAPE values between 300-700 J/kg, the convective parameters
indicate a slight chance thunderstorms is warranted this
afternoon/early evening across the mountains and deserts. With
the upper level wind flow from the northwest and mid level flow
from the northeast, could see some storms drift off the mountains
into the adjacent foothill portions of the valleys, as well as the
Santa Clarita Valley. If any thunderstorms do develop today, they
will likely be slow moving, capable of producing heavy rain with
localized flooding. Other potential thunderstorm impacts include
gusty winds, and small hail.

Meanwhile, low clouds have burned off the coast this afternoon.
NAM model cross sections showing ample low level moisture and
moderate-strong onshore flow next few days to maintain a high
probability of night and morning low clouds and fog across many
coastal/valley areas. Mild temperatures will continue next couple
of days, with gradual warming across interior sections.
While, there is some residual mid level moisture over the
mountains on Monday, only expecting some afternoon buildups
as the atmosphere begins to stabilize. By tuesday, a large
upper low begins to approach the west coast. This system will
bring an increasae in mid/high level clouds across the forecast
area.



.LONG TERM...(THU-SUN)

12z GFS/ECMWF model solutions in general agreement that a cutoff
low pressure system will likely impact the forecast area sometime
between Thursday and Friday, then slowly drift east over the
weekend. There will be a chance for hit and miss showers in most
places Thursday through Saturday (with the highest probability
from Thursday afternoon through Friday evening). Current
projections have cold core upper low (with 500 mb temperatures of
-24 degrees Celsius) moving across Southwest California sometime
between Thursday afternoon through Friday. With this cold air
aloft combined with early May sunshine providing good surface
heating, feel that there will be enough instability to warrant a
slight chance of thunderstorms(especially over interior sections),
and have added accordingly to the official forecast. This system
is cold enough that we could potentially see some snow impacts
in the local mountains, with snow levels projected to range
between 5000 and 6000 feet.

&&

.AVIATION...01/1800Z

AT 1737Z at KLAX, the marine layer depth was 3300 feet. The top
of the inversion was around 3900 feet with a temperature of 13
degrees C.

a newly reinvigorated eddy was causing some ceiling issues in
southern la county. klax remains on the north edge of the cloud
shield. the clouds over coastal la county are expected to slowly
push to the east this afternoon as the sea breeze clears the skies
for a time. elsewhere...skies will be mostly clear this afternoon
except in the mountains and deserts where a stray thunderstorm is
possible during the afternoon.

tonight...there is moderate confidence in the development of
marine clouds across the coastal and valley sections for later
this evening and overnight. there is less confidence for the
central coast.

KLAX and kbur...moderate confidence in the 18z taf. mvfr
conditions are expected for the overnight hours extending into
monday morning.


&&

.MARINE...01/200 pM...

There is rather high confidence that conds will remain below SCA
levels across the entire waters through at least Tue. Winds will
increase later in the week.


&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect until 9 PM PDT this evening
      For zones 34-35-40-41-87. (See LAXCFWLOX).
PZ...NONE.

&&

$$

PUBLIC...Gomberg
AVIATION...Sweet
MARINE...Sweet
SYNOPSIS...Munroe

weather.gov/losangeles



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