Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/24/21

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 846 PM PDT Fri Apr 23 2021

.SYNOPSIS...23/824 PM.

There will be a slight warming trend for inland areas Saturday
while overnight and morning low clouds will help to keep
temperatures cooler near the coast. Light precipitation across the
region is possible Sunday into early Monday, then afternoon
temperatures will warm notably mid week.

&&

.SHORT TERM (FRI-MON)...23/841 PM.

Upstream upper level trough passing through Northern California
tonight, maintaining a strong onshore flow pattern across
Southwest California, with LAX-Daggett gradient peaking at +9.3 mb
late this afternoon. Latest ACARS data at KLAX still showing
a deep marine layer this evening, in excess of 4000 feet.
Current satellite imagery supports this deep marine layer, with
low clouds already extending into the coastal slopes as of
830 pm. Another cool day today, with similar cool conditions
expected on Saturday, except for the Antelope Valley where highs
will continue to climb into the mid to upper 70s. Looking for
another day of strong onshore flow on Saturday, along with
a deep marine layer. This will generate gusty onshore winds across
the Antelope Valley where gusts of 30 to 40 mph will be common,
except isolated gusts up to 50 mph in the foothills. A wind
advisory may need to be considered for the Antelope Valley
for Saturday, becoming more likely on Sunday as upper level
support increases ahead of approaching weather system.

*** From previous discussion ***

A second and deeper upper low will arrive on the West Coast Sunday
morning with a cold front sweeping through the state late Sunday
into early Monday. Models have really scaled back on this system
for southern California as the upper low and most of the energy
remain well to the north and there is very little, if any,
southerly flow at lower levels to provide additional lift with the
orographics. Rain amounts have been cut in half or more in most
areas with the upper end of totals now around a tenth of an inch
with maybe a quarter inch in some of the foothill areas and
northern SLO County. An inch or two of snow possible above 6000`.

Showers expected to start during the morning or early afternoon
for northern areas and in the evening in the south. Most of the
precip should be done by sunrise Monday, though some lingering
showers possible through the day, mainly near the mountains.

.LONG TERM (TUE-FRI)...23/153 PM.

Models differ with respect to how quickly high pressure will build
behind the trough, with the GFS faster and the ECMWF still showing
another weak upper low dropping down into the trough Monday night
into Tuesday, though with minimal moisture. The main impact being
a potential delay in the warming trend as the GFS is showing the
ridge rapidly building Tue into Wed while the ECMWF is now
holding this back to late Wed into Thu. In either case,
significant warming expected for the latter half of the week,
especially inland areas. There is still quite a bit of uncertainty
whether there will be any offshore flow accompanying the ridge
which would potentially bring at least some of that warming to the
coast as well. The EC has been pretty consistent showing this
while the GFS is still showing more of an onshore pattern.

&&

.AVIATION...24/0139Z.

At 2315z at KLAX... The inversion was around 3700 feet. The top
of the inversion was around 5300 feet with a temperature of about
13 degrees Celsius.

Overall... Moderate to high confidence in the current TAFs.
North of Point Conception, MVFR CIGs will linger this evening and
may not clear at KSBP and/or KSMX or may briefly lift to above
3000 feet. If KSBP/KSMX do become VFR, IFR/MVFR CIGs will return
after 03z. KPRB will likely become and remain VFR but there is a
thirty five percent chance of IFR/MVFR CIGs returning after 08z.

South of Point Conception, MVFR CIGs will linger this evening at
most coastal and coastal adjacent sites. However, some terminals
may not clear at all and possibly will briefly lift to above 3000
feet. For Los Angeles County locations that become VFR, IFR/MVFR
CIGs return after 04z. KOXR and KCMA have a thirty percent chance
of IFR/MVFR CIGs returning after 07z and KSBA has a fifteen
percent chance. KPMD and KWJF will remain VFR throughout the
forecast period.

KLAX... Moderate confidence in the current TAF. MVFR CIGs will
lift to above 3000 feet for a few hours then IFR/MVFR CIGs return
after 04z. There will not be any east winds greater than 8 kts
during the forecast period.

KBUR... Moderate confidence in the current TAF. MVFR CIGs will
linger this evening though may briefly lift to above 3000 feet.
If the terminal does become VFR, IFR/MVFR CIGs return after 04z.

&&

.MARINE...23/818 PM.

A chance of light rain will develop across the coastal waters
Sunday into early Monday.

Across the Outer Waters... There is a thirty percent chance of
Small Craft Advisory (SCA) level winds near Point Conception
Saturday afternoon. Winds will be SCA level Monday through
Wednesday and will be strongest during the afternoon and evening
hours. Otherwise, conditions will remain below SCA level.

Across the Inner Waters north of Point Sal... SCA level winds are
likely Monday and Tuesday and will be strongest during the
afternoon and evening hours. Otherwise, conditions will remain
below SCA level.

Across the Inner Waters south of Point Conception...winds will be
SCA level across the western portion of the Santa Barbara Channel
Saturday afternoon and evening, then again Monday and Tuesday.
Otherwise and elsewhere, conditions will remain below SCA level.

&&

.BEACHES...23/845 PM.

A south swell will continue to impact Ventura and Los Angeles
County beaches through Sunday morning. The swell heights will be
up to 4 feet with periods of 18-20 seconds. This will produce
breakers up to 6 feet... locally higher on south facing beaches
through early Saturday, especially on south facing beaches of
northern Los Angeles County.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through Sunday morning for
      zones 40-41-87. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect from 3 PM to 9 PM PDT Saturday
      for zone 650. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (MON-FRI).

No significant hazards expected.

&&

$$

PUBLIC...Gomberg/MW
AVIATION...Kj
MARINE...Gomberg/KJ
BEACHES...Kj/Gomberg
SYNOPSIS...Kj

weather.gov/losangeles