571
FXUS66 KLOX 121028
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
328 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...12/0633Z.

At 0515Z at KLAX, the marine layer was 2000 ft deep. The top of
the inversion was at 3400 ft with a temperature of 25 C.

High confidence in VFR conds and winds for KPRB, KPMD and KWJF.

Moderate confidence in the remainder of TAFs. Valley TAFs may
clear an hour later than fcst. Coastal TAFs with afternoon
clearing have a 30 percent chc of no clearing. There is a 25
percent chc of LIFR cigs at KOXR, KSMO, KLAX and KLGB and a 35
percent chc of LIFR cigs at KBUR and KVNY.

KLAX...Moderate confidence in TAF. There is a 25 percent chance
of OVC008 conds 10Z-16Z. There is a 30 percent chance that CIGs
will not clear Wed afternoon. No significant easterly wind
component is expected.

KBUR...Moderate confidence in TAF. There is a 35 percent chc of
2SM BR OVC004 conds 11Z-15Z. VFR transition may be delayed until
18Z.

&&

.MARINE...11/752 PM.

Good confidence in current forecast through Thursday afternoon
with Small Craft Advisories (SCA) not expected. Increasing winds
are expected Thursday night, with SCA winds likely through the
weekend, and Gales possible Saturday afternoon/night.

Moderate confidence the forecast for the nearshore waters along
the Central Coast. SCA conditions are likely (60 percent chance)
between Friday afternoon and Sunday. There is a chance (30 percent)
of GALE force winds Saturday afternoon through Sunday evening.
Wave heights will likely peak between 8 to 12 feet.

For the outer waters, SCA winds will likely (60-70 percent)
develop Thursday night over most of the area. GALE force winds are
possible Friday through Sunday, but most likely Saturday afternoon
and night. If GALES do not develop there will be strong SCA
conditions. An extended period of steep, short period hazardous
seas with overall wave heights of 10 to 15 feet are likely between
Friday and Sunday.

For the western Santa Barbara channel SCA winds and seas will
likely develop Friday night and continue through Sunday. There is
a 30-40 percent of a period of GALE force winds focused Saturday
afternoon and evening.

For the inner waters, including the eastern Santa Barbara
Channel, wave heights along with steep choppy seas will build
Friday and continue into the weekend with a 20-30 percent chance
of SCA winds or seas.

&&

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

&&

$$

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

weather.gov/losangeles

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