Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/26/22

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 833 PM PDT Fri Mar 25 2022

.SYNOPSIS...25/654 PM.

Skies will be partly to mostly cloudy through Sunday. Rain will
develop on the Central Coast Sunday evening and spread across all
areas by Monday. Expect numerous showers on Monday, with a risk
of thunderstorms and heavy downpours, with rain diminishing on
Tuesday. Drier conditions with a slight warming trend is expected
from Wednesday through the end of next week.

&&

.SHORT TERM (FRI-MON)...25/833 PM.

A very shallow marine layer and onshore pressure trends brought
a return of low clouds and fog near immediate coastal areas today,
along with a general cooling trend to coastal areas. However,
inland areas above the marine layer remained very warm with
temperatures climbing well into the 80s to around 90 degrees
across the valleys and deserts. In fact, record high temperatures
of 87 degrees were observed today at Paso Robles, Palmdale, and
Lancaster, as well as Sandberg at 77 degrees.

Current satellite imagery showing higher level clouds continuing
to stream into Southern California from the southwest, which will
continue through Saturday. In addition, low clouds and fog also
beginning to return to portions of the coast this evening, and
will become more widespread across the coastal plain overnight
into Saturday morning. ACARS data continues to show a shallow
and strong marine inversion (around 600 feet at LAX), so there
will continue to patchy desne fog for coastal areas.

As the upper level ridge breaks down on Saturday, there will
be increasing onshore flow, with LAX-Daggett gradient likely
to peak to between +6 and +7mb by late afternoon. This increased
onshore flow will continue to bring some additional cooling on
Saturday for lower elevations, but many valley areas still
expected to be warm with highs in the lower to mid 80s. Onshore
wind gusts of 25 to 35 mph expected across the mouuntains and
Antelope Valley by Saturday afternoon/evening, with isolated
gusts as high as 40 mph in the foothills of the Antelope Valley.

*** From previous discussion ***

By Sunday the high pressure ridge shifts east of the Rockies with
southwesterly flow increasing across the West Coast. This opens
the door for additional marine layer depth and more clouds to
spill into southwest CA. A storm system will get organized over
the eastern Pacific about 500nm west of SFO Bay Sunday afternoon with
some subtropical moisture tap likely to occur from east of Hawaii.
Southerly flow increases and is likely to bring advisory level
wind gusts to many mountains and northern counties by Sunday
afternoon. This continuous south flow will likely start to
generate light precipitation for the Santa Ynez Mountains and
areas to the north late in the afternoon. Sunday night a cold
front will push through the Central Coast and move to about
eastern Santa Barbara County by daybreak on Monday. A band of
light to moderate steady rain is likely to occur with the front
lasting 4-7 hours with the front edge picking up over Los Angeles
County during the Monday morning commute. All model data are in
good consistency with the timing of the cold front, but there is
slight differences with the track of the upper level low pressure
system on Monday. The NAM model takes the more southerly track and
would bring the best dynamics to the south coast region with
stronger upslope flow, diffluent winds aloft, and rotation of the
low itself. Overall though, even the slight differences are not
enough to diminish the storm potential for widespread wetting
rainfall. If anything we favor the wetter model solutions
including EPS, due to enhanced rainfall amounts on south-facing
foothills and mountains. In addition, the air mass becomes quite
unstable by midday Monday over the coastal waters and shifts
inland through Monday afternoon and night. Surface lifted index of
-4 and MUCAPES over 600 J/kg are impressive and could bring a
rapid increase in heavy showers and isolated thunderstorms between
18Z Monday through 06Z Tuesday. Will continue to highlight 1-3"
of rain for foothills and mountains with most coasts/valleys
receiving 0.50-1.5" through Tuesday. If the storm remains on-
track, we should not be surprised to see peak amounts top out
closer to 4" or more in the Santa Barbara and western Ventura
County mountains.

Finally, snow levels will mostly be above 7000 feet on Monday but
then fall to about 5500 feet in the afternoon and Monday night.
Snow levels could dip down at times in heavier convective snowfall
Monday afternoon, so this is a concern for potential snow
accumulations at resort levels. This will not be a winter storm
that brings snow to heavily traveled highway corridors, but remote
highways leading up to higher elevations are likely to see
snowpacked and slick conditions on Monday night and Tuesday. Will
be looking at this a little closer for any highlights in the
coming day or so.

.LONG TERM (TUE-FRI)...25/223 PM.

Tuesday will be the transition day as we will continue to see
scattered showers, especially over Los Angeles County and rather
wet ground following the rain event. Temperatures will remain
cooler then normal with partly to mostly cloudy skies from the
residual moisture.

Wednesday will be the start of a drying trend. Another trough
pushes into the Great Basin late next week which steepens the
ridge just off the West Coast and increases northwest flow aloft
for our area. This may hamper a significant warm up, but there may
be another round of north-northwest winds for Sundowners during
evening/night hours or perhaps the typical I-5 corridor wind
gusts. Temperatures will remain rather cool in the mountains with
near or slightly below normal temperatures at lower elevations
next week.

&&

.AVIATION...26/0020Z.

At 0010Z, the marine inversion at KLAX was based at 500 feet. The
top of the inversion was 1500 feet with a temperature of 22
degrees Celsius.

Overall, moderate to high confidence in 00Z TAF package. High
confidence in VFR for all valley and desert TAF sites through
period. Onshore trends and shallow marine layer resulting in
low clouds lingering near immediate coastal areas late this
afternoon. High confidence in cigs returning to coastal TAFS
tonight, however only moderate confidence in timing and flight
category. Expecting LIFR/IFR conditions at coastal TAF sites
with a 20% chance of VLIFR conditions at any particular location.

KLAX...Overall, moderate confidence in 00Z TAF. High confidence
that cigs will generally prevail through Saturday morning. Cigs
mostly expected to be in LIFR/IFR category, however there is
a 20% chance of VLIFR conditions. No significant easterly wind
component is expected.

KBUR...High confidence in 00Z TAF as VFR conditions are
anticipated through the TAF period. There is a 20% chance
of MVFR VSBYs due to haze between 13Z-17Z.

&&

.MARINE...25/748 PM.

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) level northwest winds will continue through
tonight/Saturday morning before diminishing. By Sunday afternoon,
strong SCA level southerly winds will develop and continue through
the day Monday. On Monday, there is a 30% chance of Gale force
southerly winds. On Monday night, the winds will shift to the
northwest, but will remain at strong SCA levels through Wednesday.
Additionally, there will be 30% chance of Gale force winds
Tuesday and Wednesday.

For the Inner Waters north of Point Sal, high confidence in
current forecast. Through Sunday morning, winds and seas will
remain below SCA levels. On Sunday afternoon, southerly winds will
increase to SCA levels and remain at SCA levels through Monday
afternoon. Monday night, the winds will shift to the northwest
with SCA level winds expected Tuesday and Wednesday with a 20%
chance of gale force gusts.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Tonight through Sunday morning,
high confidence in winds and seas remaining below SCA levels. By
Sunday afternoon, high confidence in southeasterly winds
increasing to SCA levels and remaining at SCA levels through
Monday afternoon. The winds will shift to the west and northwest
Monday night with moderate confidence in SCA level winds Tuesday
and Wednesday, especially across western sections.

Areas of dense fog will affect most of the waters tonight into
early Saturday, then clearing to patchy dense fog through late
Saturday morning. On Monday and Monday evening, there is a slight
chance of thunderstorms. Any thunderstorms that develop will be
capable of producing brief heavy rain, small hail and possibly
even waterspouts.

&&

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

&&

$$

PUBLIC...Gomberg/EB
AVIATION...Gomberg
MARINE...RAT/Smith
SYNOPSIS...EB/Smith

weather.gov/losangeles

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