Area Forecast Discussion
Issued by NWS Los Angeles, CA
FXUS66 KLOX 302307
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
406 PM PDT SAT APR 30 2016
New Aviation Discussion
A low pressure system moving through the Great Basin will produce
a slight chance of showers and thunderstorms for eastern portions
through the weekend. Warmer weather is expected early next week as
weak high pressure builds over the region, but another low
pressure system could bring showers and cooler conditions to the
area late next week.
Satellite imagery this afternoon shows an upper low now centered
near Needles, CA. Showers have stayed mostly east of LA County
and all of the thunderstorm activity so far has been well to the
east near the center of the upper low. With very limited
instability (CAPE values of 250-500 J/kg), it`s unlikely any
thunderstorms will develop in our forecast area this afternoon. If
anything does happen, it will likely be in eastern LA County.
According to the NAM, the instability will be a little better
tomorrow with CAPE values of 500-750 J/kg, but the upper low will
be further east. Depending on what happens in the next couple of
hours, the slight chance of showers and thunderstorms may be
removed from the forecast for this afternoon and evening. We will
leave the slight chance of showers/t-storms in the forecast for
tomorrow for the Antelope Valley and mountains of Los Angeles,
Ventura, and Santa Barbara counties, but would not be surprised if
future shifts remove them.
Tonight through Monday the upper low currently near Needles, CA,
will move east and weaken below a longwave ridge. As this happens,
the marine layer will shrink but the inversion will sharpen. As a
result the night/morning low clouds and fog may because more
organized and fill in across the coastal and valley areas. This is
reflected in the current forecast. The Catalina Eddy should help
with the development of the stratus south of Pt. Conception
tonight and Sunday morning, but the Central Coast may remain cloud
free. The boundary layer moisture in the NAM suggests a better
chance for stratus on the Central Coast both Sunday and Monday
With the upper low moving east and high pressure taking over,
there should be slight warming each day through Tuesday.
Temperatures should be slightly above normal by Tuesday, with
temperatures in the 60s at the immediate coast, mid to upper 70s
for inland portions of the coastal plain, and 80s in the valleys.
Other than night/morning stratus and the slight chance of
showers/t-storms for interior areas on Sunday, generally fair
skies are expected for most of the populated areas through
Tuesday, with no wind issues anticipated.
A cooling trend should begin by Wednesday with an upper-level
trough approaching from the northwest. Models are in good synoptic
agreement that a cutoff low will develop over the area Thursday
night through Friday, then slowly drift east on Saturday. There
will be a chance for hit and miss showers in most places late
Wednesday night through Saturday. At this time, it looks like late
Thursday through Friday would be the best chance for any showers.
Thunderstorms are not in the forecast at the moment, but they may
need to be added at a later time, as 500 mb temps are as low as
-25 deg C when the center of the upper low moves overhead.
AT 2300Z at KLAX there was no Marine layer nor was there an
Good confidence in TAFs through 08Z. Lower confidence after 08Z for
coastal and vly TAFs KSBA and southward due to uncertainty in timing
of stratus arrival. Stratus could arrive at any time between 08Z and
13Z. Lower confidence in clearing fcst as BKN high MVFR or low VFR
cigs could remain late into the afternoon.
KLAX...Good confidence in TAF through 08Z. There is a 30 percent chc
of MVFR cigs 08Z-11Z. There is a 30 percent chc that MVFR cigs will
persist until 23Z.
KBUR...Good confidence in TAF through 09Z. There is a 30 percent chc
of MVFR cigs 09Z-12Z. There is a 30 percent chc that SCT conds will
develop aft 22Z.
Northwest winds will create small craft advisory conditions from
Piedras Blancas to San Clemente Island including the west portion
of the Santa Barbara Basin through tonight. Seas over 10 feet and
small craft advisory for hazardous sea conditions from Piedras
Blancas to San Nicolas Island will exist through Sunday morning as
gales north of the area persist. otherwise sca conditions are not
expected Sunday afternoon through Wednesday. Northwest winds are
expected to increase Thursday and there is a chance sca conditions
will exist over the entire area Thursday through Friday. A south
swell will build through Sunday and extra currents and surging as
well as hazardous surf are likely along exposed south facing
shores through Monday.
CA...Beach Hazards Statement in effect through Sunday evening For
zones 34-35-40-41-87. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
For zones 645-650. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 AM PDT Sunday For
zones 670-673-676. (See LAXMWWLOX).