Area Forecast Discussion
Issued by NWS Los Angeles, CA
FXUS66 KLOX 301842
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1142 AM PDT MON MAY 30 2016
It will be another day of slow clearing, especially for the
beaches. A ridge will build in Tuesday through Thursday, bringing
well above normal temperatures to the valleys and interior. There
will continue to be overnight and morning low clouds and fog,
especially at the beaches through the period.
Visible satellite imagery shows marine layer stratus well
entrenched along the Southern California Coast this morning.
The coastal valleys are struggling to scour out this morning. A
deep marine layer has deepened to near 3100 feet at KLAX this
morning, with a strong marine inversion above it. More May Gray is
on the way, especially as ridging aloft over the Eastern Pacific
Ocean builds in. A trough of low pressure over the Lower Colorado
River Basin will continue to move east and be replaced by the
ridge. Subsidence aloft will clamp down on the marine layer,
lessening its areal extent but creating a May Gray/June Gloom
scenario. If KLAX NAM BUFR time height sections are correct, the
marine layer depth will thin to near 1000 feet by Thursday
morning. Clouds will hug the coast over the next several days
as the marine inversion tightens. Out of the marine influence,
temperatures will warm above normal over the next several days.
The warmest temperatures will likely occur in the Antelope Valley,
where temperatures might approach the century mark by Thursday.
With the trough exiting today, enough instability exists to
produce a few cloud buildups or maybe an isolated shower or
thunderstorm over the San Gabriel Mountains this afternoon and
An update has been issued to the package this morning.
The ridge will continue to build on Tuesday. The 582 dm hgts
moving into the area will squash the marine layer down and there
will less vly penetration. The squashing of the marine layer hgt
and the warming aloft will really put a strong inversion cap on
the marine layer and this will allow the low clouds to stay over
the beaches. Not much change in the coastal temps but the vlys
will have a big warm up and the there will be further warming in
the interior as well.
Wed and Thu will be dominated by ridging with the 585 DM ridge
axis sitting over the state. There will only be a few clouds in
the lower vlys as the marine layer will be smooshed below 1000
feet. There will still be low clouds during the night through
morning hours across the coasts. There will only be a slight
warming trend across the coastal sections and maybe no warming at
the beaches. It will be a different story in the vlys where max
temps will jump into the mid 80s Wed and then the lower to mid 90s
on Thu. Thursdays max temps will be 8 to 12 degrees above normal.
There will be upper 90 degree readings in the interior of SLO
county and perhaps a few triple digit max temps in the Antelope
Thursday looks to be the warmest day of the week for many areas as
thickness values peak. Warmest valleys expected to climb to around
90 degrees, with Antelope Valley climbing to around 100 degrees.
A shallow marine layer will continue to keep coastal low clouds
and fog. Friday through Sunday, 12z GFS and ECMWF models showing
another cutoff low developing off the Southern California coast,
with cross sections showing a good surge of mid and upper level
clouds. With this type of pattern, not out of the question that
we could see some showers or mountain tstms develop across the
forecast area sometime during this period, but probability at this
time is still around 10 percent.
At 1710Z at KLAX...the marine layer was about 2550 feet deep. The
top of the marine inversion was near 3930 feet with a temperature
of 20 degrees Celsius.
A slow clearing trend is expected today with most TAF sites
clearing by late this afternoon, yet clearing is not a complete
guarantee for all coastal sections. The marine layer is currently
2500 feet deep, but the depth of the marine layer is expected to
decrease tonight and Tuesday to about 1700 feet. The marine clouds
are expected to sneak into the TAF sites in the San Fernando
Valley tonight, with IFR conditions the result.
KLAX...There is moderate to high confidence in the 18Z TAF. MVFR
to isolated IFR conditions are expected tonight into Tuesday
morning. There is a 30 percent chance of marine clouds arriving
plus or minus two hours from forecasted times.
KBUR...There is low to moderate confidence in the 18Z TAF. The
greatest uncertainty in this forecast is in regards to whether the
marine clouds will make it into the airfield tonight. There is a
40 percent chance of VFR conditions through the night.
Conditions will likely remain below advisory levels through at
least Friday. The northwest swell across the coastal waters will
diminish through the middle of the week. A long period south swell
is expected to reach the coastal waters by Tuesday then peak on
Wednesday and Thursday before gradually diminishing. The swells
will likely remain below advisory criteria but there will be
extra surging and currents along exposed south facing shores.