428
FXUS66 KLOX 121753
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1053 AM PDT Wed Jun 12 2024

Updated Aviation Discussion

.SYNOPSIS...12/858 AM.

Low clouds and fog are expected through at least Friday across
coast and coastal valleys with temperatures 3-6 degrees below
normal. Gusty north winds are expected Friday night into the
weekend, mainly in the mountains and southern Santa Barbara County
and adjacent coastal waters. Warming temperatures are expected
this weekend, with faster clearing of low clouds.

&&

.SHORT TERM (TDY-FRI)...12/908 AM.

***UPDATE***

Marine layer depth is around 2000-2500 feet this morning and
covered the entire coast and most of the coastal valleys. A
moderate onshore trend today will again keep clouds along the
coast much of the day but clear across the valleys by late
morning. Temperatures will remain below normal in most areas
through at least Friday, but near to slightly above normal across
the interior. An upper low continues to spin a few hundred miles
to our southwest and will remain there through tonight but will
begin to move northeast Thursday and likely be over the San Diego
area Thursday afternoon before moving into AZ Friday.

***From Previous Discussion***

The lower hgts and weak PVA associated with the low will lift the
marine to over 3000 ft. Low clouds will overspread all the coasts
and vlys and likely penetrate deep into the mtn passes. This
amount of lift will also likely produce a good amount of drizzle
or even light rain near the foothills. Clearing will be slow and
if the marine layer deepens enough the vly clouds will morph into
a field of strata- cu. Onshore flow will remain near 9mb to the
east and it will be another day of slow to no clearing across the
coasts. The low will bring some mid level dynamics into the area.
This along with the very high sun angle will destabilize the
atmosphere over the mtns. There is, however, only a very thin
slice of mid level moisture and this will eliminate the threat of
convection. There will likely be some CU or ACCAS clouds over the
LA/VTA mtns in the afternoon. The marine layer, onshore flow and
lower than normal hgts will all contribute to max temps 3 to 6
degrees below normal with the exception of the Antelope Vly which
will end up about 3 degrees above normal. This is the most likely
scenario. There is a 20 percent chc that the upper low will weaken
the marine inversion either by mechanical mixing or cool air
advection into the inversion layer. If this happens there will be
much less low clouds and a substantial warm up.

Both today and Thursday afternoons the strong 9mb onshore push to
the east will generate gusty winds across the Antelope Vly and its
western foothills. While there will likely be isolated advisory
level gusts the majority of the winds will be under advisory
levels.

A big change in Srn CA`s weather will begin on Friday as the upper
low departs the area. Quickly rising hgts, sunny skies and
offshore trends will bring 4 to 8 degree of warming to all areas
save for the coast where the marine layer and onshore flow will
still hold sway.

High pressure will build into the northwest to north in the
afternoon. All of the N/S gradients will quickly reverse from
onshore to offshore. These sfc gradients will combine with modest
NW flow aloft to produce Sundowner wind event across Srn SBA
county. Current ensemble guidance gives an 80 percent chc of
advisory level wind gusts and a 20 percent chc of warning level
gusts. It will be windy through the I-5 corridor as well with a 50
percent chc of advisory level gusts. These north winds will
greatly reduce the marine layer clouds.

.LONG TERM (SAT-TUE)...12/327 AM.

Saturday will be a very warm day. Hgts will approach 590 dam and
there will likely be offshore flow from both the north and east.
The offshore push from the east is not strong to generate much in
the way of NE winds and the winds will remain predominately from
the north. Low clouds will likely be confined to the Long Beach
area. Most areas will warm 6 to 12 degrees. The coasts will end up
2 to 4 degrees above normal and inland areas 6 to 12 degrees. The
one exception will be the SBA south coast where a forecast max
temps of 85 degrees or 15 degrees above normal. Northerly advisory
level winds will remain likely over portions of SBA county. These
winds and max temps will combine with low humidities to produce
enhanced fire weather conditions. Please reference the fire
weather discussion below for more exact details.

Deterministic and ensemble forecasts agree that an upper low over
the PAC NW will bring a troffier pattern to the state and hgts
will lower to about 580 dam. Offshore flow will continue at the
sfc but it will be a little weaker than on Saturday. Some marine
layer clouds may develop across western SBA county and the Long
Beach area, but would not be surprised if skies ended up totally
clear. Max temps are forecast to lower each day. The blended
ensemble guidance may be a little too aggressive with the cooling
because the offshore flow effects would likely overwhelm the
synoptic scale cooling.

Onshore flow returns on Tuesday and along with continued troffing
aloft should result in more marine clouds and temps cooling to
near normals.

&&

.AVIATION...12/1753Z.

At 17Z at KLAX, the marine layer was 2500 ft deep. The top of the
inversion was at 5300 ft with a temperature of 21 C.

High confidence in VFR conds for KPRB, KPMD and KWJF thru the
period.

Low clouds were widespread in all coastal and valley areas this
morning, with the exception of the interior valleys of SLO County
and the Cuyama Valley. Conditions were mostly IFR to MVFR.

Based on the latest observational trends, expect cigs to scatter
out by this afternoon in the valleys and coastal plain north of
Pt. Conception. However, MVFR cigs are expected to linger near the
coast and over the coastal valleys south of Pt. Conception thru
the day. Expect widespread low clouds in all coastal and valley
areas again tonight, with the exception of the interior valleys of
SLO County and the Cuyama Valley. Conds should be mostly IFR to
low MVFR, except locally LIFR to VLIFR in the foothills and north
of Pt. Conception. In addition, accompanying the low clouds, there
will be a 50-70% chance for vsbys to become MVFR tonight/Thurs
morning and drizzle will be possible in a few areas (40% chance).

KLAX...Moderate confidence in TAF. There is a 20-30% chance that
cigs scatter out this afternoon. There is a 40% chance of IFR
conditions between 09Z and 15Z Thu. Any east wind component should
remain weaker than 7 kt.

KBUR...Moderate confidence in TAF. There is a 20-30% chance that
cigs do not scatter out. There is a 40% chance of IFR conditions
between 09Z and 15Z Thu.

&&

.MARINE...12/426 AM.

In the outer waters, good confidence in the forecast. Winds and
seas are expected to remain below Small Craft Advisory (SCA)
levels thru Thu afternoon, then an extended period of strong NW
winds is likely. SCA winds are likely Thu night, except maybe not
until Fri in the southern zone (PZZ676). SCA level winds and seas
are a near certainty (95% chance) Fri thru Mon. There is a 50-60%
chance of Gale force winds Fri afternoon or evening thru early Mon.
There is even a 20-30% chance of STORM Force wind gusts (to 48 kt
or greater) at times Fri night thru Sun night, mainly during the
evening hours.

In the inner waters N of Pt. Sal, conditions will likely remain
below SCA levels thru Fri morning. SCA conds are likely (80% chance)
Fri afternoon thru Sun night. Winds may drop below SCA levels for
a few hours during the late night thru morning hours, but seas will
likely remain at or above SCA levels. There is a 40-50% chance of
Gale force winds during the afternoon/eve hours Sat and Sun.

In the Santa Barbara Channel, conds will likely remain below SCA
levels thru Thu afternoon. There is a 30% chance of SCA level
winds in western portions Thu night. SCA level winds are likely
(80% chance) across western portions of the SBA Channel during
the late afternoon thru late night hours Fri thru Sun, with a 40%
chance of Gale force winds during these hours Sat and Sun. In the
eastern portion of the SBA Channel, SCA conds are likely (60-70%
chance) during the late afternoon thru late evening hours Fri thru
Sun. Steep waves of 8 to 12 ft are likely late Fri thru Mon.

In the southern inner waters, forecast confidence is lower. There
is a 30% chance of SCA level W-NW winds in northwestern portions
Fri afternoon/evening, and a 60% chance of SCA conds Sat afternoon
thru Sun night, mainly from Anacapa Island to Malibu. There will
likely be steep and dangerous seas, possibly to SCA levels Sat-Mon.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...MW/Rorke
AVIATION...DB/Cohen/Lewis
MARINE...DB
SYNOPSIS...MW

weather.gov/losangeles

Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox