449
FXUS66 KLOX 171014
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
314 AM PDT Tue Sep 17 2024

.SYNOPSIS...16/841 PM.

Much cooler than normal temperatures will continue through Friday
before warmer conditions return for the weekend. There is a
chance of rain or drizzle Wednesday night and Thursday as a low
pressure system moves into the area.

&&

.SHORT TERM (TDY-THU)...17/242 AM.

A fairly unusual pattern for mid September as Srn CA is in between
a departing upper low and an approaching upper low. All of the
cold air form ydy`s low destroyed the marine inversion and low
clouds are confined to western SBA county. Rising hgts, plenty of
sunshine and weak onshore flow will bring 2 to 4 degrees of
warming to the csts/vlys and 4 to 8 degrees for the mtns and
interior. Despite this warming max temps will end up 10 to 15
degrees blo normals.

The next upper low will start its trek down the west coast early
Wednesday and by noon it will be just west of the Bay Area. The
marine inversion should reform and this along with stronger
onshore should allow for a little more coastal stratus to form
esp for the Central Coast and the LA cst. A slight chc of rain
will develop in the afternoon over SLO county as the low moves
further south. Max temps will warm a degree or two south of Pt
Conception and will cool a degree or two north.

The low with 563 dam central hgt will continue to move south
overnight and by dawn Thursday it will be centered just to the
north of SLO county. A chance of rain will overspread SLO And SBA
counties overnight. There is a slight chc of rain for VTA and LA
counties but more likely the upper low will gin up a deep marine
layer cloud deck and some drizzle (which could produce a few
 of an inch) Rainfall amounts overnight will not total any more
than .05 inches.

The upper low will skirt along the northern portion of the
forecast area on Thursday. It will bring cloudy skies and chc of
rain to the entire area. The system does not have much moisture to
work with and rainfall amounts will be under a tenth of an inch
with the only exception being the NW corner of SLO county which
could see a quarter inch. The cold core of the upper low will move
over the area in the afternoon and the instability created by the
cold temps aloft could be enough for TSTM development. At this
time there is only a 10 percent chc of a TSTM but the threat will
need monitoring.

Max temps on Thursday will plummet along with the quickly lowering
hgts and cloud cover. Look for 4 to 8 degrees of cooling across
the board with max temps coming in 10 to 20 degree blo normals.
Look for max temps in the 60s across the coasts and 70s in the
vlys.

Breezy northwest to onshore winds are likely Wednesday into
Thursday with the most wind prone areas potentially reaching
advisory levels.

.LONG TERM (FRI-MON)...17/312 AM.

All signs point to a robust warming trend starting on Friday. Both
the GFS and EC show a rapid rise in hgts to 588 or even 590 dam.
At the same time onshore flow weakens considerably with a
possibility of weak offshore flow during the morning hours. Marine
layer clouds will likely be confined to western SBA county.

6 to 12 degrees of warming is on tap for Friday with 5 to 10
additional degrees slated for Saturday. Sunday will be warmer
still but only be 1 or 2 degrees. Slight cooling is forecast
Monday as the hgts fall and onshore flow increases.

The weekend temps will be 4 to 8 degrees above normal with 70s at
beaches 80s a little further inland and 90s in the vlys, lower
elevation mtns and inland areas.

&&

.AVIATION...17/0656Z.

At 0541Z at KLAX, the marine layer was 4600 feet deep. The top of
the weak marine inversion was near 9000 feet with a temperature
around 8 degrees Celsius.

High confidence for TAFs at KPMD and KWJF.

Low-moderate confidence in all remaining TAFs. Sites north of
Point Conception have the best chance for cigs and there is a
chance for LIFR cigs/vsbys at KSMX (30%) between 10Z and 16Z.
Cigs may oscillate between flight categories tonight into Tuesday
morning.

KLAX...Moderate confidence in TAF through 18Z. There is a chance
for MVFR conditions from 12Z to 14Z, however the more likely
solution appears to be VFR conditions through until Tuesday
night. No significant east wind component expected.

KBUR...Low to moderate confidence in TAF due to potential for
brief MVFR cigs around 15Z.

&&

.MARINE...16/929 PM.

For the Outer Waters (Central Coast to San Nicolas Island),
moderate to high confidence in the forecast. For the northern zone
(Pt Piedras Blancas to Pt Sal) winds are likely to remain below
SCA level until Tues afternoon, then there is a 60-80% chance of
SCA level winds developing Tues afternoon thru Wed morning. From
Wed afternoon thru late Sun, moderate confidence in winds
remaining below SCA level, with a 30-50% chance of SCA winds Fri
thru Sun, with best chances Sun. For the southern zones (Pt Sal
to San Nicolas Island) moderate to high confidence in SCA level
winds persisting into early Wednesday, with a lull possible
Tuesday morning. There is a 40-60% chance of SCA winds continuing
thru late Wed. There is a 30-60% chance of SCA level winds Thurs
thru Sun, with best chances Fri afternoon thru late night.

For the Inner Waters off the Central Coast. High confidence winds
will remain sub advisory level thru tomorrow morning, then there
is a 60-80% chance of SCA winds in the afternoon thru evening
hours Tues. Moderate confidence in winds being sub advisory Wed
thru Sunday, with lowest confidence in the afternoon thru evening
hours Fri thru Sun.

For the Santa Barbara Channel, high confidence in Gale Force
thru late tonight, then rapidly decreasing to below SCA level.
Steep, choppy seas and strong rip currents can be expected thru
late tonight. There is a 40-70% chance in SCA level winds
returning Tues and Wed afternoon thru late night, with higher
confidence Tues. From Thurs to Sun, There is a 20-50% chance of
SCA level winds in the afternoon thru evening hours, with highest
confidence Fri.

For the nearshore waters off the Los Angeles and Orange County
coasts, SCA level winds will continue throughout much of the
zone. In the northwest portion of the zone from Malibu west to the
Channel Islands and as far south as Santa Barbara Island, high
confidence in Gales thru late tonight. Seas will be choppy in
this area, and exposed beaches may see strong rip currents. Winds
will quickly drop off to below SCA levels overnight into early
Tues. Moderate to high confidence in winds remaining below SCA
level Tues afternoon thru Sun.

&&

.BEACHES...16/927 PM.

A series of Southern Hemispheric storms will send a long-period,
South to Southwest swell (around 18-second wave periods) to the
Southern California coastal waters through the middle of this
week. Wave periods will gradually shorten to around 15 seconds by
late week. This S to SW long-period swell will bring an extended
period of elevated surf -- surf heights of 4-6 feet -- along with
powerful and dangerous rip currents (over 80% chance) through
Thursday. The area of greatest concern for these impacts will be
across beaches with highest exposure to S to SW swell directions
-- especially across the L.A. and Ventura County beaches. These
 factors warrant the issuance of a Beach Hazards Statement for the
 L.A. and Ventura County beaches.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Wednesday for zones 645-650-670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Wednesday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke
AVIATION...Phillips
MARINE...Lewis/JB
BEACHES...Phillips/Lund/JMB
SYNOPSIS...MW

weather.gov/losangeles

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