Scientific Forecaster Discussion
fxus66 klox 251219
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
519 am PDT sun Jun 25 2017
..aviation discussion updated...
A strong ridge of upper-level high pressure over southern Arizona
will continue very warm conditions away from the coast through
early next week. Closer to the coast, a persistent marine layer
should moderate temperatures and continue mainly night through
morning low clouds and fog. A trough of low pressure off the
California coast will weaken high pressure aloft Tuesday and
bring a cooling trend as onshore flow strengthens.
Today will be the last day of increasing temperatures. There are 2 mb
offshore trends both form the north and the east. These trends
have greatly reduced the marine layer which will be confined to
the central coast and the la coast. There will be some northerly
winds as well. The upper level ridge will actually shift a little
to the east today and this will take a couple of degrees away from
the Max temps across the interior today (not that there is much
difference between 110 and 108 degrees). The reduced marine layer
and offshore trends will combine to bring several degrees of
warming to the coasts and vlys. The Santa Clarita Vly will warm
enough to justify a heat advisory.
Monday's marine layer stratus pattern will be pretty similar to
this morning's...perhaps just a touch more.
The ridge will be knocked down by a pac northwest trof on Monday and hgts
will drop to about 590 dm which is still very warm but still
noticeably cooler than today's 594 dm hgts. There will not be
much change in Max temps across the coasts but the vlys will see 2
to 4 degrees of cooling and the interior will see a very welcome
4 to 8 degrees knocked of the Max temps.
There does not look like there will be much change in the stratus
Monday night as the pressure grads will be unimpressive and there
will not be an eddy. So it looks like most areas except the la
coast and central coast will be cloud free Monday night.
The ridge will continue to be smooshed down to the south. There
will also be an increase in the onshore flow both to the north and
the east. Look for cooling across the entire area. There deserts
will further cool and will only be about 4 degrees above normal
(down from 14 degrees above today)
The long term looks like a pretty typical June scenario. Weak
broad scale troffing will cover the west Wed and Thu. At the sfc
the onshore flow will slowly increase each day. Both of these will
combine and allow for an increase in coverage of the night through
morning low clouds. Hgts will lower a bit more on Wednesday as
well and then hold steady on Thu. Look for Max temps to come in
right at normals on Wed and remain about the same on Thu.
A subtle reversal occurs Friday with a slight increase in hgts and
a small decrease in the onshore flow. There will be little or no
change to the marine layer stratus pattern but Max temps will
bounce up a few degrees.
At 09z at klax... the inversion was around 700 feet. The top of
the inversion was around 3050 feet with a temperature of about 31
Overall... low confidence in the current coastal tafs and
moderate to high confidence in the remaining tafs. Vlifr/LIFR
conditions are along the coast but just off terminal sites at many
locations. It is difficult to judge which locations may have cigs
and possibly visibility take a nose dive at sunrise. Chances are
greatest for at least IFR/MVFR conditions to come in at central
coast and Ventura County sites and at worst MVFR conditions at
ksba and Los Angeles County sites. Any reduced conditions should
be VFR by 18z. Otherwise and elsewhere conditions will be VFR
through the forecast period.
Klax... low confidence in the current taf. IFR/MVFR conditions
may move over the airfield near daybreak and there is a ten
percent chance that LIFR conditions could develop suddenly that
time. However there is a sixty five percent chance of remaining
VFR. VFR conditions will prevail by 18z and continue through the
forecast period. There is a thirty five percent chance of
IFR/MVFR conditions after 26/10z. No east winds stronger than
seven knots are expected during the forecast period.
Kbur... moderate to high confidence in the current taf. There is
a less than ten percent chance of MVFR conditions around daybreak.
Otherwise VFR conditions will prevail through the forecast
For the outer waters... Small Craft Advisory (sca) level
conditions will continue through at least Tuesday evening. Wind
speeds may weaken to below Small Craft Advisory levels during the morning hours but
will strengthen again in the afternoon.
For the inner waters... Small Craft Advisory level winds will develop in the afternoon
and evening hours through Tuesday evening across the northern
nearshore waters as well as in the east Santa Barbara Channel.
Local gusts up to 25 kt could also develop during this time from
Point Mugu to San Mateo Point west of Santa Catalina Island.
In addition to the elevated winds, a short period west to
northwest swell could impact the coastal waters Monday through
Fire weather...24/800 PM.
Hot and dry conditions will continue through Monday. The hot and
unstable conditions will also bring the potential for plume
dominated fires which can create their own intense winds. Gusty
onshore winds will continue today focusing the concerns to
interior Los Angeles County. Gusty west to northwest winds will
impact interior portions of the forecast area through Monday.
For Los Angeles County, the focus of strongest winds will be the
I-5 corridor in the mountains as well as the Antelope Valley where
gusts between 30 and 40 mph can be expected. For Santa Barbara
County, the strongest sundowner winds will be focused across the
western portions of the Santa Ynez range and South Coast (mainly
from Gaviota to goleta), with gusts in the 30 to 40 mph range each
evening. Humidities in the single digits and teens can be
expected across the mountains, deserts, and interior valleys. In
addition, localized humidities falling to between 15 and 25
percent can be expected in the Santa Ynez Mountains and adjacent
canyons where the downslope sundowner winds develop.
The combination of hot and dry conditions with locally gusty winds
will bring elevated fire weather concerns to interior sections
through Monday, with brief critical conditions likely each
afternoon and evening in wind prone areas. If fire ignition
occurs, dangerous fire behavior should be expected. As such, the
public should be extreme careful when handling potential ignition
sources such as cigarettes, campfires, hand torches and metallic
California...heat advisory in effect until 9 PM PDT this evening for zones
38-52>54-88. (See laxnpwlox).
Excessive heat warning in effect until 9 PM PDT this evening
for zone 59. (See laxnpwlox).
Pz...Small Craft Advisory in effect from 9 am this morning to 3 am
PDT Wednesday for zone 645. (See laxmwwlox).
Small Craft Advisory in effect until 3 am PDT Wednesday for
zones 650-670-673-676. (See laxmwwlox).
Hazard potential outlook...(tue-sat)
no significant hazards expected.