Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/05/22

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 816 PM PDT Wed May 4 2022

.SYNOPSIS...04/1212 PM.

High pressure will persist through Friday with warm temperatures
inland and mild conditions near the coast. A cold front will usher
in cooler and windy weather for the upcoming weekend. The cool
and unsettled weather pattern will remain over southwest
California early next week.

&&

.SHORT TERM (WED-SAT)...04/815 PM.

***UPDATE***

Overall, a quiet evening across the forecast district. Latest
satellite and surface observations indicate stratus/fog along the
Central Coast as well as surging through the Santa Barbara
Channel. Current AMDAR sounding data indicates marine inversion
around 1000 feet deep. No significant winds are observed with just
the usual onshore gusts of 15-25 MPH.

Forecast-wise for the immediate short term, main issue will be the
marine layer stratus/fog. With onshore gradients overnight and
weak eddy circulation, stratus/fog should be able to form nicely,
impacting the entire coastal plain overnight. Do not anticipate
much deepening of the inversion overnight, so will only expect
limited penetration into the coastal valleys overnight. A quick
look at the latest HREF data supports this forecast thought. Other
than the stratus/fog, skies should remain clear overnight. No
significant wind issues are expected.

Overall, current forecast has good handle on the immediate short
term. Will likely make some minor tweaks to the sky grids, based
on trends of the stratus. However, no significant updates are
expected at this time.

***From Previous Discussion***

Offshore pressure gradient trends continue to weaken this
afternoon with return flow breezes pushing through Ventura County
to near the LA County line. This resulted in stunted temperatures
near the coasts where northeast winds never materialized, as
expected. Inland valleys, however, have warmed nicely into the 80s
and near 90 just after noon. Low clouds had mostly dissipated over
the nearshore waters south of Pt Conception, but cloud fragments
remain in the channel while a much stronger push of low clouds
were rapidly approaching Morro Bay from the north. Expect all
coastal areas to have low clouds and fog tonight and Thursday
morning as onshore pressure gradients increase. Then for Thursday,
gradients peak at +8mb for LAX-DAG which will result in slow
clearing at the coasts and gusty southwest winds through the
highway 14 corridor to the Antelope Valley foothills/canyons in
the afternoon. Temperatures will be similar to today for the most
part, with the exception of the Central Coast where winds off the
cold ocean water will hold down much heating potential.

Thursday evening will begin the next round of Sundowner winds for
the western Santa Ynez Range, possibly reaching advisory levels.
Across southern counties the onshore pressure gradient is a little
stronger Friday afternoon so expect slight cooling for most areas
compared to Thursday. The marine layer and May Gray will likely
hang around longer and possibly penetrate into coastal valleys by
Friday morning. A cold front will be dropping down the northern
CA coast Friday afternoon as a deep low pressure system approaches
the Pac Northwest states. Winds increase over the coastal waters
Friday night with a dry cold front entering the area. Sundowner
winds will be more widespread Friday evening, but again higher
gusts for western canyons.

Saturday will be the transition day to a colder and windier
pattern ahead. The cold front will push through the entire region
with gusty west to northwest winds for coastal waters, I-5
corridor and much of the northern counties. Temperatures will
still be rather mild with a few 80s over the interior valleys.
Winds will be more widespread and strongest over coastal waters
and higher elevations.

.LONG TERM (SUN-WED)...04/145 PM.

Amazingly good agreement with all deterministic model data and
especially GEFS, EPS, GEM ensembles for the large Pac Northwest
low pressure trough to adsorb another system from the Gulf of
Alaska on Sunday. This secondary system substantially drops the
base of the large scale trough southward late Sunday and Monday
closer to central CA. EFI wind gusts are shaded 90 percent
probability with a +1 bullseye for the Santa Barbara and San Luis
Obispo County areas including nearshore coastal waters, and the
GEFS has a large area of >34 kt winds in this region for Sunday
afternoon. Much of the area will likely see gusty west-northwest
winds with anticipation of needing several high end wind
advisories and possibly high wind warnings for the mountains and
Antelope Valley. Mother`s Day activities may be less impacted if
completed earlier in the day rather than later.

The deep low pressure system drops over northern CA on Monday
reinforcing colder air and continuing the windy theme. The system
slowly moves over central CA and weakens through Wednesday. NBM
precipitation chances only rise to about 15-20 percent anytime
from Monday through Wednesday, however, there will be good
cyclonic flow and slight instability that may help generate a few
showers during these days. This part of the forecast remains
somewhat uncertain, but we`re not really expecting much impact
from precipitation. Snow levels will drop to about 3500 feet or
less by Monday morning since the airmass will be so anomalously
cold. If any organized precipitation did occur, and models
currently do not support this, then the low snow levels would be a
concern. Additional reinforcement of cold air could keep the
trough entrenched across western states through the remainder of
next week.

&&

.AVIATION...04/2340Z.

At 2130Z, the marine layer at KLAX was 850 feet deep. The top of
the inversion was around 1700 ft with a temperature of 24 C.

Moderate confidence in coastal and valley TAFs, except lower
confidence in the LA Valley sites. Low clouds are expected at all
coastal terminals, generally IFR south of Pt. Conception, LIFR
along the Central Coast. There is a 30 percent chance that low
cigs make it to KBUR and a 20 percent chance for KVNY.

KLAX...Moderate confidence in the 00Z TAF. The arrival time of IFR
cigs could differ by +/- 2 hours from taf time of 08Z. East winds
are not expected.

KBUR...Low to moderate confidence in the 00Z TAF. There is a 30%
chance of IFR conditions from 11Z-15Z.

&&

.MARINE...04/806 PM.

For the Outer Waters, moderate to high confidence in the
forecast. Winds and seas are expected to remain below Small Craft
Advisory (SCA) levels thru Thu, though there could be local SCA
level wind gusts late Thu afternoon. SCA level winds are expected
Thu night through Mon, with a 50% chance of Gale force winds Sat
through Mon.

For the Inner Waters north of Pt. Sal, moderate confidence in the
forecast. Winds and seas should remain below SCA levels thru Thu
morning. There is a 50% chance of SCA level winds Fri
afternoon/evening, then SCA level winds are likely Sat thru Mon.
There is a 30% chance of Gale force winds during the afternoon and
evening hours Sat and Sun.

For the Inner Waters south of Pt. Conception, moderate confidence
in the forecast. Winds and seas are expected to remain below SCA
levels thru Fri afternoon, except for a 30% chance of SCA level
winds Thu evening across the western Santa Barbara Channel. For
Friday night thru Sunday, high confidence in SCA level winds
across much of the SBA channel. Across the southern inner waters,
there is a 40% chance of SCA level winds Fri night, then SCA conds
are likely Sat thru Mon. There is a 40% chance of Gale force
winds during the evening hours Sat and Sun across most of the
Santa Barbara Channel and across the western portion of the waters
west of LA County. The strongest and most widespread SCA to Gale
Force winds will occur on Sunday late afternoon/evening.

Short period seas will grow rapidly across all of the
waters, building to 12-15 feet in the outer waters, 10-13 feet
nearshore along the Central Coast, and to 8-12 feet over the
nearshore waters south of Point Conception by Sunday evening.

&&

.BEACHES...04/149 PM.

A long-period southerly swell and an increase in northwest swell
could bring high surf conditions with hazardous rip currents to
the Central Coast as early as late Thursday, and to beaches south
of Point Conception Saturday through Tuesday. Also, locally
generated short period swells may develop this weekend,
potentially increasing beach hazards for many coastal areas.

&&

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

&&

$$

PUBLIC...EB/Thompson
AVIATION...Smith
MARINE...Smith
BEACHES...Sweet/Munroe/DB
SYNOPSIS...EB

weather.gov/losangeles

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