609
FXUS66 KLOX 171545
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
845 AM PDT Sat Aug 17 2024

.SYNOPSIS...17/323 AM.

Onshore flow will bring some cooling and night and morning low
clouds and fog near the coast, otherwise mostly quiet weather is
expected through next week. A warming trend will develop early
next week. Hazardous heat will be possible next Tuesday or
Wednesday for the interior.

&&

.SHORT TERM (TDY-MON)...17/844 AM.

***UPDATE***

Over the local area this morning -- increased moisture on the
periphery of a midlevel speed maximum moving across the central
Great Basin, decreased midlevel heights in the base of a deep
upper trough centered over the Pacific Northwest and offshore,
and diffusion of an eddy off the coast of the Southern California
Bight -- have all contributed to the marine layer doubling to
tripling in depth during the past 24 hours. Data from KLAX suggest
marine-layer depths this morning now upwards of around 2200-2300
feet. This will allow the increased expanse of marine stratus and
fog -- as depicted by ongoing satellite imagery and surface
observations -- to persist with a longer duration and greater
coverage today. As a result, the forecast has been updated over
coastal areas and coastal valleys to account for these trends.
Clearing toward the coast is still expected later today. A repeat
of high-coverage/duration marine stratus and fog is expected once
again tonight into Sunday morning -- owing to little change in the
synoptic pattern over the local area. No other changes have been
made to the ongoing forecast.

***From Previous Discussion***

Fairly benign weather across the area this weekend with increasing
onshore flow and slightly cooler temperatures. Most areas will be
at or slightly below seasonal normal temperatures. Marine layer
stratus covers most of coastal LA and Ventura counties this
morning and a little bit along the Central Coast. Low clouds
expected to clear by mid to late morning in most areas. A similar
pattern expected Sunday morning as well.

A warming trend is expected to begin Monday as high pressure once
again pushes into California from the east. Ensemble based
guidance shows valleys and interior areas getting back up to
102-105 Monday and Tuesday and low 90s around Downtown LA. While
these numbers are very borderline for heat risk, there`s a 20-30%
chance that temperatures will be a few degrees warmer, pushing heat
risk levels to advisory or warning criteria for areas away from
the immediate coast.

Models showing little to no monsoon moisture moving into our area
the next several days so thunderstorm chances are very low.

.LONG TERM (TUE-FRI)...17/352 AM.

High pressure is expected to weaken mid to late next week
bringing temperatures back down closer to normal levels by
Thu/Fri. With a trough returning to the West Coast onshore flow
will be increasing with stronger afternoon and evening winds
across the interior. This upper pattern is not favorable for
thunderstorms locally so dry weather expected through the period.

&&

.AVIATION...17/1245Z.

At 1128Z at KLAX, the marine layer was 2000 ft deep. The top of
the inversion was near 2900 ft with a temperature of 23 deg C.

High confidence in TAFs for KPRB, KBUR, KVNY, KPMD, and KWJF.

Moderate confidence in the Los Angeles County coastal TAFs.
Cig/vsby restrictions may shift between MVFR to IFR through 14Z.
Cig burn off time may be as late as 20Z. Cigs may return as early
as 03Z Sun.

Low confidence in remaining coastal TAFs. Cigs may scatter as late
as 20Z and return as early as 06Z. There is a 20-30% chance KSBP
and KSMX remain VFR thru the period.

KLAX...Moderate confidence in TAF. Dissipation of cigs may be as
late as 20Z, with a return as early as 03Z. No significant east
wind component is expected.

KBUR...High confidence in TAF. Flight cat changes may be off by
+/- 2 hours.

&&

.MARINE...17/319 AM.

For the outer waters from the Central Coast to San Nicolas Island,
high confidence in Small Craft Advisory (SCA) level winds for the
waters south of Point Sal through Monday (Zones PZZ673/676). For
the furthest northern zone (PZZ670), high confidence in SCA level
winds this morning, then moderate confidence as winds winds will
be at or just below advisory levels through Monday morning.
Better confidence in SCA level winds Monday afternoon through
mid-week, with a 20% chance of Gale Force wind gusts at times
early next week.

For the nearshore waters off the Central Coast, moderate
confidence in conditions remaining below SCA levels through
Monday, with a 30% chance of SCA winds during the afternoon-
evening hours through Wednesday.

For the Santa Barbara Channel, moderate confidence in winds across
the Western Portion of the channel, with a 30% chance of advisory
level winds each afternoon and evening through Wednesday. In the
eastern portion, high confidence in conditions remaining below SCA
level through Wednesday.

For the southern inner waters, high confidence in conditions
staying under SCA levels through the period.

With a shallow marine layer, moderate confidence in patchy dense
fog with visibilities under 1 nautical mile effecting the Central
Coast waters and southern inner waters this morning, and again
tonight through Sunday morning.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 9 AM PDT this morning
      for zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Monday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Cohen/MW
AVIATION...Lund
MARINE...Lund/Smith
SYNOPSIS...Hall

weather.gov/losangeles

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