Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
220 PM PDT Friday Jul 29 2016
High pressure aloft will result in above normal temperatures away
from the coast through the middle of next week. Night through
morning low clouds and fog will affect coastal and some valley areas
during the period. There will also be some afternoon clouds over the
mountains and deserts. Otherwise, mostly clear skies will prevail
across the region. Breezy afternoon and evening south to west winds
can be expected through the middle of next week as well.
Some low clouds lingered at the beaches along the central coast
early this afternoon. Otherwise, mostly sunny skies covered the
forecast area. A few pop-up cu developed over the vtu/l.A. County
mtns and Antelope Vly as well. Gusty S to W winds up to 30 mph were
noted across the foothills, mtns and deserts thanks to decent
onshore gradients. Temps this afternoon soared into the 90s to
around 100 in the vlys and foothills, with temps 102 to 110 observed
in the Antelope Vly. Two record highs have already occurred, with a
high of 102 at Sandberg (old record 100 in 1995) and a record-tying
high of 109 so far at Lancaster Fox Field (old record 109 set in
Fairly strong upper level ridging will persist over srn California thru Mon.
500 mb heights of around 594 dm today will lower slightly to 591 to
592 dm for sun and Mon. 1000-500 mb thicknesses will range from 584
to 588 dm this afternoon then drop to 580 to 585 dm by sun and
continue on Mon. The marine inversion which is below 1000 ft today
should gradually increase to near 1500 ft over the weekend and into
Mon, with very good onshore gradients forecast by the NAM up to +9.0
mb lax-dag each afternoon.
Marine layer clouds and fog should expand along the coastal plain
and extend into some of the adjacent vlys night and morning hours
thru Mon. Afternoon clouds should also develop over the mtns and
deserts each day with marginal amounts of monsoonal moisture
filtering into the area from the E at mid levels. A 10 percent or
less chance of a thunderstorm cannot be ruled out as well in the
mtns and deserts, which is too small a chance to mention in the
zones. Otherwise, mostly clear skies will prevail thru Mon across
the forecast area. Gusty afternoon and evening S to W winds will
persist across the foothills, mtns and deserts during the period.
The onshore flow and gradually deeper marine layer will help to
lower temps some thru the weekend and into early next week. Even so,
highs will remain several degrees above normal away from the coast.
Highs by sun in the warmest vlys and foothills will be in the upper
80s and 90s, except upper 90s to 103 in the Antelope Vly. Temps will
then change little for Mon.
Ec/GFS in good agreement during the extended period. The upper
ridging will continue over srn California Tue thru Thu, then weaken slightly
Fri as upper troffiness develops along and off the central coast.
Some monsoonal moisture will affect mainly eastern l.A. County Tue
into Wed, with some afternoon cu buildups possible in the mtns and
deserts, but no thunderstorms are expected. The marine layer pattern
will continue thru the week, with varying amounts of night and
morning low clouds and fog for the coast and some adjacent vlys.
Otherwise, mostly clear skies will prevail across the region. Little
change in temps are forecast Tue thru Fri, with highs several
degrees above normal away from the coast. The warmest vlys and
foothills each day should reach the upper 80s and 90s, with
upper 90s to 103 expected for the Antelope Vly.
At 1030z, the marine layer was around 750 feet deep at klax. The
top of the inversion was near 4000 feet with a temperature around
29 degrees celsius.
North of Point Conception...moderate confidence in coastal tafs, with
marine layer clouds moving in overnight, with lower confidence in
timing. Cigs expected to fall to LIFR but 30% chance of IFR conditions.
S of Point Conception...low to moderate confidence in 18z tafs
for coastal sites...high confidence inland. There is a 30% chance
that low clouds will not affect the klax...klgb or koxr. A 40%
chance ksba will remain VFR.
Klax...low to moderate in taf...due to uncertainty in timing and
height of marine layer cigs overnight. There is a 20% chance of
IFR cigs...and a 30% chance the site will remain clear.
Kbur...high confidence in VFR conditions through the period.
Moderate to high confidence with the forecast through this
weekend. Not expecting Small Craft Advisory winds, except for the coastal areas
around Point Conception where local gusts to 25 kt will be
possible through this evening. There is a 40% chance that gusts
could become more widespread and the Small Craft Advisory might need to be added
during the evening. Otherwise no significant issues across the
coastal waters through this weekend.
A small but long period southerly swell will develop Sunday into
Hot and dry conditions continue with widespread temperatures
currently in the 90s and 100s and relative humidities in the 10s to
low 20s across interior areas. Locally gusty onshore winds will
continue during the afternoon and evening hours across portions of
the Los Angeles mountains into the Antelope Valley through at least
early next week. Gradually improving relative humidities and cooler
temperatures will help to reduce fire weather concerns including
over the sand fire this weekend into early next week as high
pressure aloft weakens and is gradually replaced by a weak low
pressure aloft off the coast of northern California.