Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/03/22

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 829 PM PDT Sat Apr 2 2022

.SYNOPSIS...02/715 PM.

A deep marine layer combined with onshore winds will keep low
clouds over the coasts and into the valleys for the weekend.
Gusty north to northwest winds will move in Sunday night, mainly
for southern Santa Barbara County, the Interstate 5 corridor, and
Antelope Valley. Temperatures will warm through the week, becoming
hot by Wednesday/Thursday.

&&

.SHORT TERM (SAT-TUE)...02/829 PM.

A weak upper level trough passing through California tonight
combined with strong onshore flow near the surface has resulted
in a deep marine layer pattern. Latest ACARS data showing the
marine layer depth in excess of 3000 feet across the LA Basin.
Current satellite imagery showing an extensive area of low
clouds across the forecast area, along with an influx of higher
level clouds. The 00z NAM model is showing the deep moist layer
continuing into Sunday morning, which could result in some patchy
drizzle across LA county, especially the foothills of the San
Gabriel mountains where upslope flow is enhanced.

Projected northwest-north wind event will on track for the area
late Sunday into Tuesday, with wind advisories likely needing to
be issued.

*** From previous discussion ***

Sunday will start off as a quiet day under fairly zonal flow.
During the evening a weak shortwave will move across the area with
broad, dry northwest flow aloft behind it. Low clouds should be
able to clear much better in the late morning or afternoon,
especially for northern areas. Gusty north to northwest winds will
be the story Sunday evening through the overnight hours as a
strong offshore trend in northerly gradients combines with very
good upper-level wind support and decent cold advection. As is
typical, areas with the strongest winds will be across southern
Santa Barbara County, through the I-5 corridor, and the western
Antelope Valley. Wind gusts of 30-50 mph are likely for these
areas, with some isolated gusts to 60+ mph for the typical north
wind magnets. Wind Advisories will likely be needed. The gusty
north winds should keep low clouds from returning from Santa
Barbara northward on Sunday night, but not enough to prevent them
from covering coastal LA and Ventura Counties.

Winds will weaken through Monday morning, but the lull will be
short-lived. Northerly gradients strengthen even further Monday
night. A note of significance is the SBA-BFL gradient forecast to
strengthen to the realm of -5.5 to -6.5 mb. Taking a glance at
our local pressure gradient study, a LAX-BFL gradient in this
range puts it in the 97th percentile for early April. In addition,
upper-level wind support is forecast to be stronger and a tight
thermal gradient will produce much stronger cold advection. As a
result, stronger north to northwest winds are expected as compared
to Sunday night for the same areas listed above. Gusty winds will
likely be more widespread on Monday night, especially for the
eastern half of the Santa Ynez range. It will certainly be
possible for the hills above Montecito to see localized gusts
above 60 mph. The question will be if winds filter into the
urbanized foothill areas along the eastern south coast. Winds may
also filter through the Santa Clarita and western San Fernando
Valleys, although not nearly as strong. Confidence is high that
we`ll need another round of Wind Advisories for southern Santa
Barbara County, the I-5 corridor, and Antelope Valley. Future
shifts may need to consider whether a High Wind Watch will be
necessary for the mountains. Winds will start to taper off through
the first half of Tuesday. Once again north winds will pick up on
Tuesday evening, but thanks to northerly gradients and upper-level
support relaxing winds will be weaker.

Outside of winds, the other weather topic of note will be warming
temperatures on Monday and Tuesday. Downsloping wind from the
mountains will help the valleys warm up into the low to mid 80s
by Tuesday.

.LONG TERM (WED-SAT)...02/238 PM.

A big change is in store mid to late next week as an upper-level
ridge starts to build over California on Wednesday then peak on
Thursday. The main weather items for those days everyone will be
talking about will be heat and offshore winds. Starting with wind,
both the GFS and ECMWF show light to moderate offshore LAX-DAG
gradients. They agree that Wednesday night through Thursday
morning will be the peak timing for strongest winds. Currently,
upper-level support does not appear very strong. The ECMWF meteogram
for Newhall indicates that the ensembles are in fairly good
agreement in moderate offshore winds in the 30-40 mph range.
However, a few of the members show some stronger gusts both days,
so confidence in strength is still fairly low at this time.
Confidence is better in terms of timing as the ensembles also
agree Thursday looks a bit stronger than Wednesday.

A building ridge combined with offshore flow will bring the
potential for hot temperatures across LA and Ventura Counties.
High temperatures will make a jump into the 80s with a few spots
in the low 90s on Wednesday. The peak heat is expected on Thursday
and Friday. There still is some uncertainty in exactly how warm it
will be since we`re still 5 to 6 days out. The current forecast
indicates widespread temperatures in the 85-95 degree range away
from the beaches. This puts temperatures around 15 to 20 degrees
above normal. Current record high temperatures are quite high so
they may be hard to reach. However, there is the potential for a
couple records to be broken Thursday and Friday.

Temperatures will dramatically sink back into the 70s and low 80s
on Saturday as a trough approaches the west coast with a return of
the marine layer.

&&

.AVIATION...03/0028Z.

At 2251Z at KLAX, the marine layer was 3700 feet deep. The top of
the inversion was around 4300 feet with a temperature of 16 C.

Expect widespread low clouds in all coastal and most valley areas
tonight. Expecting mostly MVFR conditions, except IFR to LIFR
conds are possible on the Central Coast. Lower confidence in
timing of cat changes.

KLAX...Low to moderate confidence in 00Z TAF. There is a 30-40%
chance that cigs will linger all afternoon. East wind component
will remain below 7 kts.

KBUR...Moderate confidence in 00Z TAF. There is a 20-30% chance
that cigs will linger through at least 21Z.

&&

.MARINE...02/233 PM.

For the Outer Waters, moderate to high confidence in current
forecast. Small Craft Advisory (SCA) level winds are expected to
affect the northern two outer waters zones (PZZ670/673),
particularly across western sections at times thru Sun morning.
Winds may actually drop below SCA level in most areas tonight, but
seas should remain above SCA levels. Across the southern zone,
winds and seas should remain below SCA levels thru Sun morning.
NW winds are expected to increase across the entire outer waters
Sun afternoon, with a 60% chance of Gale Force winds Sun
afternoon thru Tue evening. A Gale Warning has been issued for the
outer waters from Sunday afternoon through Tuesday evening. Then,
SCA conds are expected Tue night and Wed.

For the Inner Waters north of Point Sal, winds and seas will
likely remain below SCA levels thru Sun morning. SCA level NW
winds are expected to develop Sun afternoon, then continue much of
the time thru Tue evening. There is a 30% chance of Gale force
winds Mon afternoon and evening.

For the Santa Barbara Channel, winds and seas will remain below
SCA levels through early Sun afternoon. SCA level W-NW winds are
expected across western sections of the Channel Sun afternoon and
Sun night, then across most of the SBA Channel Mon thru Tue night.

Across the southern inner waters, there is a 30-40% chance of SCA
level W-NW winds across western sections Mon afternoon thru Tue
evening. Otherwise, SCA conds are not expected.

&&

.BEACHES...02/233 PM.

A passing storm system on Sunday will bring gusty northwest winds
to the coastal waters with building surf conditions on area beaches,
mainly late in the day. Surf will remain elevated through Monday
night, then another long period northwest swell from a second
storm moving across the north Pacific Ocean will move into the SW
California coastal waters. Surf will likely increase further for
Tuesday and Wednesday, with the potential for high surf
conditions, especially on west-facing beaches. In addition, high
tide predictions are around 5 feet next week, which could generate
minor beach erosion along with the building surf.

High surf along with increasingly warm temperatures in the 80s
to 90s by mid-week may lure people to area beaches for relief.
Ocean water temperatures are only in the 50s, which can easily
cause hypothermia and immediate danger to those entering the
water. The combination of high surf and cold water will be
dangerous to unprepared swimmers or surfers. Powerful waves are
likely with a high rip current risk late Sunday through Wednesday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 PM PDT Sunday for
      zones 670-673. (See LAXMWWLOX).
     Gale Warning in effect from 3 PM Sunday to 9 PM PDT Tuesday
      for zones 670-673-676. (See LAXMWWLOX).
     Small Craft Advisory in effect from 9 AM to 3 PM PDT Sunday
      for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...Gomberg/Stewart
AVIATION...Phillips/Sweet
MARINE...Sweet/DB
BEACHES...Sweet/DB
SYNOPSIS...Phillips/Stewart

weather.gov/losangeles

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