Scientific Forecaster Discussion
fxus66 klox 221818 aaa
Area forecast discussion...updated
National Weather Service Los Angeles/Oxnard California
1118 am PDT Fri Jun 22 2018
Updated aviation discussion
An upper level high pressure will result in hot weather across
inland areas today. A trough dropping through the Pacific
northwest will bring a cooling trend, and same night to morning
low clouds pattern is expected over the weekend. Warming trend
will return early to mid week.
Short term (tdy-sun)...22/934 am.
Big contrast in temps from coast to inland areas again today as
we still have a robust 2000' marine layer but at the same time we
also have a little warming aloft and about a 1mb offshore trend in
the west/east gradients. So while this won't help lower
elevations much in terms of warming it should generate a degree or
two of warming for the mtns and Antelope Valley as well as
interior slo/sb counties. This is all covered pretty well in the
existing forecast so no changes there. Temps are encroaching on
heat advisory criteria but just in isolated pockets and it's not
expected to be widespread enough to warrant pulling the trigger on
***From previous discussion***
An upper low will drop southward through Idaho tonight and
Saturday, and heights across the region will drop a bit. Onshore
gradients should increase as well. An eddy circulation will
develop across the inner waters, which would deepen the marine
layer a bit. Overall though, expect a similar low cloud pattern
tonight/Sat morning, with widespread clouds in all coastal and
valley areas with the exception of the far interior valleys of slo
County and the Cuyama Valley. Max temps should be down a few
degrees in most areas, except there will be minor changes near the
coast. Cooling should be most pronounce in the warmer valley
locations of l.A. And vtu counties on Sat. Gusty winds in the
Antelope Valley could approach advisory levels Sat afternoon.
The upper low will move into The Rockies Sat night and sun, with a
very weak broad trough extending into the forecast area. Models
are showing a rather strong southerly surge will be located just
east of the region Sat night and Sunday, which should help deepen
the marine layer and bring cool marine all the way to the coastal
slopes. Models show significant cooling at 950 mb on sun. Expect
plenty of night through morning low clouds, possibly to the
coastal slopes, with slower clearing on Sunday. Clouds may well
linger through the afternoon in coastal areas south of pt
Conception on Sunday. There should be significant cooling in all
areas west of the mtns on Sunday, with the exception of portions
of the Santa Ynez Valley and the central coast, where downslope
southerly winds will provide warming in places like Lompoc and
vandenberg. There will be less cooling in the higher mtns and
Long term (mon-thu)...22/407 am.
Heights will rise a bit across the region on Monday, and onshore
gradients will relax a bit, especially in the north-S direction.
Expect faster clearing on Mon, and with some warming at 950 mb,
there should be a few degrees of warming in the valleys and across
interior sections of the coastal plain, generally to a bit above
normal levels. It will remain hot in the mtns and deserts, with
temps several degrees above normal. Do not expect too much change
in the weather Tue and Wed, with night through morning low clouds
in coastal and most valley areas, and mostly minor changes in Max
temps. A trough moving into the West Coast should bring cooling to
most areas on Thu.
At 1737z, at klax, the marine layer depth was around 1900 feet deep.
The top of the marine inversion was around 3100 feet with a
temperature near 26 degrees celsius.
Moderate confidence overall in the 18z tafs. Low clouds with
IFR/MVFR cigs are expected at ksba, koxr, kcma, ksmo, klax and klgb
til around 20z-21z then the low clouds should move back into all the
coastal airfields from late this afternoon at ksmo and klax, and
thru this evening to later tonight at the rest of the coastal
airfields. Some of the airfields should have LIFR conditions at
times late tonight into Sat morning as well. The low clouds with
IFR/MVFR cigs should also move into kbur and kvny late tonight. The
low clouds are expected to persist thru much of Sat morning altho
some scattering to VFR cigs should occur at ksbp, ksmx, kbur and
kvny by 17z Sat. The timing of the onset and dissipation of the low
clouds and timing between flight cats may be off +/- an hour or two.
There is also a 30% chance the low clouds may not affect kbur and
kvny at all during the period.
For kprb, kpmd and kwjf, there is hi confidence in the 18z tafs with
VFR conditions thru Sat morning. Gusty southwest afternoon and
evening winds will prevail at kpmd and kwjf during the taf period as
Klax...moderate confidence overall in the 18z taf. Low clouds with
MVFR cigs are expected at the airfield til around 21z then the low
clouds with ifr\mvfr cigs should move back in by 00z late this
afternoon and persist thru about 20z Sat. The timing of the onset
and dissipation of the low clouds and timing between flight cats may
be off +/- an hour or two.
Kbur...moderate confidence overall in the 18z taf. Low clouds with
ifr\mvfr cigs should move into the airfield by 09z late tonight then
clear to MVFR vsbys around 17z Sat. Otherwise, VFR conditions should
prevail for the most part. The timing of the onset and dissipation
of the low clouds and timing between flight cats may be off +/- an
hour or two. However, there is also a 30% chance the low clouds may
not affect the airfield at all during the period.
For the outer waters, high confidence in current forecast. Small
Craft Advisory (sca) level winds will continue through Saturday
morning with a 60% chance of Small Craft Advisory level winds continuing into
Saturday evening. Winds will remain below Small Craft Advisory levels Sunday and
Monday. On Tuesday, there is a 70% chance of Small Craft Advisory level winds.
For the inner waters, high confidence in current forecast. For the
waters north of Point Sal, winds and seas will remain below Small Craft Advisory
levels through Tuesday.
For the waters south of Point Conception, winds and seas will
remain below Small Craft Advisory levels through Tuesday. However, both
tonight/Saturday morning and again Saturday night/Sunday morning,
southeast winds are anticipated with a 50% chance of southeast
wind gusts between 10 and 15 kt.
Fire weather...22/944 am.
Elevated to brief critical fire weather conditions are expected
to continue across interior areas through Saturday due to the
combination of hot temperatures, low humidities, and breezy
conditions. A 2000 foot marine layer will continue to keep coastal
and valley temperatures mild today, however a weak offshore wind
influence this morning across interior sections will bring additional
warming to the mountains, deserts, and interior valleys above the
marine influence. This offshore wind influence has already brought
some wind gusts in the 20 to 25 mph range across the mountains
this morning, with a rapid drop of humidities into single digits.
This offshore wind influence is expected to bring widespread
triple digit temperatures today across the lower mountains,
Antelope Valley, and interior valleys of San Luis Obispo County.
In addition, these same areas will see widespread single digits
humidities. Later this afternoon through tonight, winds will shift
to the west and northwest across interior sections with gusts
in the 25 to 35 range, with strongest winds in the mountains.
In addition, the hot and unstable conditions will also bring the
potential for large plume growth with any fire ignitions that
develop across interior sections.
On Saturday, a stronger onshore wind influence will bring a slight
cooling to most areas, however there will still be some
triple digit readings and single digit humidities across warmest
interior locations. In addition, there will be stronger onshore winds in the
afternoon and evening, with gusts in the 30 to 40 mph range across
the mountains, interior valleys, and Antelope Valley, with isolated
gusts as high as 50 mph possible in the foothills of the Antelope
Valley. This increased wind threat combined with continued hot and dry
conditions will bring more elevated to brief critical fire weather
conditions across interior sections on Saturday, especially the Highway
14 corridor from Santa Clarita valley into the Antelope Valley.
Pz...Small Craft Advisory in effect until 9 am PDT Saturday for
zones 670-673. (See laxmwwlox).
Small Craft Advisory in effect until 3 am PDT Saturday for
zone 676. (See laxmwwlox).
Hazard potential outlook (sun-thu).
No significant hazards expected.