Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 281155
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
455 AM PDT Sun May 28 2017

...Aviation discussion updated...

.SYNOPSIS...

An upper level ridge of high pressure and a lowering marine layer
will support a warming trend through early next week. The high will
be replaced by a weak upper level trough of low pressure by the
middle of next week providing a cooling trend with more widespread
night and morning low clouds for the coast and valleys.

&&

.SHORT TERM...(TDY-TUE)

Pleasant but rather dull on tap for the next three days. All mdls
agree that a 582 DM ridge will persist over the area today and
Monday with a trof moving into the area Monday night and lasting
into Tuesday.

Marine layer stratus is struggling to develop due to a weak
inversion and offshore trends. The only exception is western SBA
county where westerly flow has produced a backwards building
stratus deck. Patchy stratus will develop towards dawn over the LA
and VTA coasts and the San Gabriel Vly as continued radiational
cooling increases the low level humidities close to 100%.

Whatever the morning stratus pattern skies everywhere will be
sunny by mid to late morning. The increasing hgts...offshore
trends and abundant sunshine will all contribute to 3 to 6 degrees
of warming across the area and most max temps will end up 2 to 4
degrees above normal.

Not much change in the weather for Monday. The stratus may be a
little better developed as the inversion will be stronger. Max
temps will be up 1 to 2 degrees from todays readings.

Tuesday will see the arrival of a weak trof along with an increase
in the onshore flow both to the west and north. This will likely
spin up an eddy. Look for significant increase in morning low
cloud coverage esp for the vlys. Still the onshore flow and the
inversion will not be strong enough to prevent total clearing Max
temps will fall with the biggest drops in the vlys and the
smallest inland.

.LONG TERM...(WED-SAT)

The GFS and EC agree that a fairly sharp (at least for this time
of year) upper level trough will move across the forecast area on
Wednesday. This system will continue to deepen the marine layer
which will continue to cool the coasts and vlys. Lowering hgts
will allow some cooling inland also. The PVA with this trof moves
across during max heating and while it is still on the dry side
there is a 20 percent chc of a TSTM.

A little ridge will bring a decrease in marine layer coverage as
well as a noticeable bump up in temps on Thursday.

The forecast is a little muddled for Friday and Saturday as the
GFS continues the ridge while the EC brings in a weak trof. The
night through morning low cloud pattern should continue but to
what degree will be dependent on which pattern actually develops.

&&

.AVIATION...28/12Z.

At 09z at KLAX... The inversion was based near 500 feet. The top
of the inversion was near 4900 feet with a temperature of about
17 degrees Celsius.

Overall... Moderate confidence in the current TAFs. LIFR/IFR
conditions will develop at some coastal locations by 14z then
will clear by 18z. There is a fifteen percent chance of LIFR/IFR
conditions at KBUR and KVNY in the 13z-17z period and a ten percent
chance at KPRB and KSBA in the 14z-17z period. LIFR/IFR conditions
will likely develop at most coastal and adjacent valley locations
after 29/04z. Otherwise and elsewhere VFR conditions will
prevail.

KLAX... Moderate confidence in the current TAF. There is a thirty
percent chance of LIFR/IFR conditions in the 13z-17z period then a
seventy percent chance in the 29/05z-17z period. Otherwise VFR
conditions will prevail. No east winds above 7 knots are expected.

KBUR... Moderate confidence the current TAF. There is a fifteen
percent chance of LIFR/IFR conditions in the 13z-17z period then a
sixty percent chance after 29/05z. Otherwise VFR conditions will
prevail.

&&

.MARINE...28/200 AM.

Small Craft Advisory (SCA) conditions continue across the Outer
Waters into at least Tuesday though there will be periods during
overnight and early morning hours when winds dip below SCA levels.

SCA conditions will begin in the nearshore waters of the Central
Coast this afternoon and continue into at least Tuesday. There
will be periods during the overnight and early morning hours when
conditions will dip below SCA levels. The stronger winds will
spill into the western half of the Santa Barbara Channel each
evening but not far enough to warrant a SCA for the entire
channel.

The elevated winds will create a short period chop over all
waters including the Santa Barbara Channel and Santa Monica Basin
in the Inner Waters. The winds peak Monday and Tuesday and there
is a thirty percent chance that Gale Conditions form beyond 30 nm
of the Central Coast.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 9
      AM PDT Tuesday for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 AM PDT Tuesday for
      zones 670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(TUE-SAT)
No significant hazards expected.

&&
$$

PUBLIC...Rorke
AVIATION...Kj
MARINE...Kj
SYNOPSIS...Sirard

weather.gov/losangeles



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