-- Discussion containing changed information from previous version are highlighted. --
706
FXUS66 KLOX 121304
AFDLOX

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

.SYNOPSIS...12/106 AM.

Low clouds and patchy night to morning fog and drizzle are
expected through late this week over the coast and coastal
valleys. This will bring highs in the 60s near the coast to 80s
and 90s over the interior. Gusty southwest winds will affect the
Antelope Valley through late this week. Winds will shift to
northwest to north Friday night into the weekend, with moderate to
locally strong winds over the higher terrain. Warming temperatures
are expected this weekend, with fairly good clearing to the
coast.

&&

.SHORT TERM (TDY-FRI)...12/311 AM.

A 578 dam upper low will spin harmlessly to the SW of KLAX today.
Strong onshore flow both to the north and the east has combined
with the weak lift from the upper low to deepen the marine layer
to over 2000 ft. Low clouds now cover all of the coasts and vlys
(including the Santa Clarita) and extend onto the mtn foothills.
The weak lift and deepening marine layer will also allow some
patchy drizzle to develop. Continued strong onshore flow will
delay clearing esp for the coastal sections. Many beaches and
nearshore areas will see no clearing today. The interior will cool
some with slightly lower hgts and some cool marine layer
intrusion. The Atascadero to Paso Robles area will see a 20+
degree cool down as south flow brings cool marine air into the
area. Short range ensemble based fcsts show some warming along the
coasts today and this seems a little overdone (based on the
marine layer and strong onshore flow) and these max temps were
lowered.

The upper low will move to the east and will be centered over San
Diego by late afternoon. 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...
-- Changed Discussion --
12/1304Z.

At 12Z at KLAX, the marine layer was 2300 ft deep. The top of the
inversion was at 4800 ft with a temperature of 23 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 LIFR, except
low MVFR in coastal sections of L.A./VTU Counties, and the locally
VLIFR in the foothills and north of Pt. Conception. There could be
some drizzle this morning. Expect cigs to scatter out by mid to
late morning in the valleys and early afternoon on the coastal
plain. However, cigs may linger near the coast 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.

KLAX...Moderate confidence in TAF. There is a 20-30% chance that
there will be no clearing at all this afternoon. There is a 20%
chance of IFR condition 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
will not scatter out until 21Z. There is a 20-30% chance that cigs
tonight will arrive as early as 06Z.
-- End Changed Discussion --

&&

.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...Rorke
AVIATION...DB
MARINE...DB
SYNOPSIS...Cohen/Smith

weather.gov/losangeles

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