Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/30/20

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 843 PM PDT Sat Aug 29 2020

.SYNOPSIS...29/802 PM.

Southwest flow aloft will keep near normal temperatures in place
along with night through morning low clouds across coast and
coastal valley areas through Monday. Gusty onshore winds will
continue across the interior each afternoon and evening into early
next week. A strong high pressure system is expected to bring a
warming trend Tuesday through Thursday, leading to another
potential significant heat wave Friday through Labor Day weekend.

&&

.SHORT TERM (SAT-TUE)...29/840 PM.

Onshore flow and a persistent marine layer will remain in place
across the area as southwest flow aloft continues ahead of a weak
upper-level trough. The latest AMDAR soundings from KLAX show a
marine layer depth near 1200 feet deep currently, deepening
slightly to near 1500 feet along the Central Coast. Minor
variations in the marine intrusion will likely keep temperatures
near seasonal levels. Night through morning low clouds and fog
will continue to push into the coast and most valley areas through
at least Monday.

The weak upper-level trough of low pressure off the Central Coast
of California will slowly retrograde to the southwest through
Sunday then exit the region between Monday night and Tuesday.

No changes are planned to the current forecast at this time.

***From Previous Discussion***

High temperatures on Monday will change little from Sunday. There
could be a few high clouds moving across the southern portion of
the forecast area as models are picking up on some remnant mid
level moisture from what is now Tropical Storm Iselle (pronounced
ee-sell) located 800 miles south of San Diego this afternoon.
This remnant moisture will be caught up in the southwest flow
aloft with the bulk of moisture south and east of the forecast
area, generally across the southeast portion of California and
Arizona.

A strong upper level ridge of high pressure will begin to build
in across California, leading to some light northeast flow in the
boundary layer across the interior. This rising height and light
northeast flow across the interior will likely result in a slight
warming trend for Tuesday (mainly interior areas) that will
continue through the remainder of the week.

.LONG TERM (WED-SAT)...29/159 PM.

Models continue to remain in good agreement for the extended
period (Tue-Fri) showing good confidence for a warm midweek, then
hot by the end of next week into the Labor Day weekend. By
Tuesday, an elongated 594 DM high pressure aloft slides in from
the Ern Pac across Cal. This high expands over the Southwestern
states on Wed and persists over the region through the weekend.
The high strengthens to a 597-599 DM by Friday and remains through
next weekend. This will bring steady warming each day to the
mountains and interior valleys. Onshore flow at the coast will
remain moderate and should keep the marine layer across coastal
areas and limit any warming for the coastal and valley sections.
By Friday, onshore flow will be weaker and much of the forecast
area will really heat up. This widespread warm up will at least
persist, if not increase over the holiday weekend, and Heat
Advisories and/or Excessive Heat warnings may be need late
next week into the Labor Day weekend.

Besides the heat, the placement of the upper level high will
bring a prolonged period of SE flow aloft by Fri. If there is
moisture to tap into, the placement of the upper high will be
conducive to open a window for convection to our south, which
would provide an upstream moisture and thunderstorm source for our
mountains and deserts by the end of the week. Still too far out
to grab onto details.

&&

.AVIATION...30/0053Z.

At 2315Z, the marine layer was 1400 ft deep at KLAX. The top of
the inversion was around 2900 ft with a temperature of 25C.

Moderate to high confidence in the 00Z TAFs. High confidence in
desert and valley terminals with the exception of KBUR, where
there is lower confidence for the occurrence of MVFR conditions.
Moderate confidence for coastal terminals, with uncertainty in
the arrival time of the low clouds, which could be off +/- an hour
or two.

KLAX...Moderate confidence in the 00Z TAF. Low clouds may arrive
as early as 05Z tonight. High confidence in no significant east
winds.

KBUR...Moderate confidence in the 00Z TAF. There is a 30% chance
of 0 cigs overnight. The arrival time of any low clouds may occur
between 10Z and 12Z.

&&

.MARINE...29/814 PM.

Overall, high confidence in forecast through Tuesday, then
moderate confidence. Winds and seas will likely remain below Small
Craft Advisory (SCA) level through Tuesday. However, local gusts
to 20 kt are possible during the afternoon and evening hours
through the Santa Barbara and San Pedro Channels. For Wednesday
and Thursday, there is a 30-40% chance of SCA level winds across
the outer waters along Point Conception to San Nicolas Island.

Patchy fog, locally dense with visibility under one mile, will
likely affect the waters through Sunday morning.

&&

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

&&

.HAZARD POTENTIAL OUTLOOK (TUE-SAT).

Very warm conditions are expected by the end of next week, with
an increased risk for heat related illnesses possible through
Labor Day weekend.

&&

$$

PUBLIC...Hall/Gomberg
AVIATION...Phillips/Sirard
MARINE...Stewart/Phillips
SYNOPSIS...Hall

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