Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/07/23

Area Forecast Discussion

National Weather Service Des Moines IA

 646 PM CDT Sat May 6 2023

...Updated for the 00z Aviation Discussion...

.DISCUSSION.../Tonight through Saturday/
Issued at 222 PM CDT Sat May 6 2023

Key Messages:

- Conditional chance for storms, possibly severe far south this
  evening.
- Dense fog could develop overnight.
- Another chance for strong to severe storms Sunday afternoon and
  night.
- Mainly quiet and mild next week.

An active weather pattern will continue through Sunday night across
the area. Surface low pressure is located over northeast Kansas this
afternoon with a warm front extending east towards the Kansas City
and St. Louis metros. This boundary will lift some into this evening
as the upper level flow becomes a bit more southwesterly as a short
wave passes through the region. The warm front will likely stall
near to just south of Iowa before retreating back south as the
current surface low washes out and new cyclogenesis takes over in
western Kansas.

For Iowa, an elevated mixed layer (EML) has been expanding into
central Iowa and model solutions continue to be different in the
evolution of the EML with the HRRR continuing to be the most robust
developing convection along the warm front in northern Missouri with
some expansion into south central Iowa this evening. ACARS soundings
a various points across the region continue to show an increasingly
stout EML capping the region. Cloud cover is mixed across that area
of interest and actually have backed high temperatures off a few
degrees north of the warm front. Should convection not develop with
diurnal heating and forcing, the low level jet is not overly
impressive and with the primary kinematic energy with the passing
short wave well north of the warm front, confidence in storms let
along areal coverage is not high. In a worst case scenario should
the capping break, conditions are favorable for a few supercells
capable of large hail and possibly tornadoes in vicinity of the warm
front with increasing curvature in the low level hydrographs and
potential for streamwise vorticity ingestion. Otherwise regarding
storms, the overnight should be generally quiet outside what is
mentioned above.

The other weather concern overnight is the increasing potential for
fog and potentially dense fog. The greatest chances should be along
and north of Interstate 80 and possibly southward into the
Nishnabotna Valley. The fog may take some time to dissipate into
Sunday. On Sunday, the warm front will advance back north. For EML
will either still be in place or become re-established and keep any
surface based activity to a minimum though there is some potential
of convective elements to overtop the EML with elevated
thunderstorms possible as the day goes on. Eventually, stronger
forcing and eroding capping may lead to thunderstorms to develop
later Sunday afternoon with additional activity overnight. Again,
supercells would be possible near the warm front which could include
all phases of severe weather potential though development still is
conditional on the EML eroding. Storms overnight could become linear
as they move out of Nebraska and would bring an attendant damaging
wind threat though the 0-3 km theta-e differences of less than 20C
are not overly favorable for established cold pools.

Mild and spring like conditions will continue for much of next week.
After Sunday night, a transition to more westerly/zonal upper level
flow early in the week to ridging by mid-week. No single focused
period for precipitation during this period though residual chances
are still in the forecast at times. An upper level low will lift
into the western High Plains towards the end of the week which often
would lead to storms in Iowa but this system eventually drifts north
and shears out into next weekend so it may not have much impact on
the state.

&&

.AVIATION.../For the 00Z TAFS through 00Z Sunday evening/
Issued at 638 PM CDT Sat May 6 2023

An area of stratus and fog in northern IA are creating MVFR and
IFR conditions, with occasional drops into LIFR. This stratus and
associated fog is currently eroding from the west, but will
expand south and west again when temperatures cool this evening.
This will result in worsening conditions statewide, with
widespread IFR ceilings and low visibility likely at all sites at
some point through the night.

In addition to stratus, showers and thunderstorms are expected to
develop south over the next few hours, potentially impacting KDSM
and KOTM. Confidence is low in the exact location and time storms
will initiate, with higher confidence for storms at KOTM and less
at KDSM. Therefore, will watch radar trends closely this evening
and update TAFs accordingly.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

DISCUSSION...Donavon
AVIATION...Dodson



Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 836 PM PDT Sat May 6 2023

.SYNOPSIS...06/803 PM.

Dry and slightly warmer conditions are expected this weekend into
next week, though temperatures will remain below normal through
next Wednesday. Much warmer temperatures are possible towards the
end of next week, especially inland.

&&

.SHORT TERM (SAT-TUE)...06/835 PM.

A couple of weak upper level low pressure systems will rotate into
northern California during the next 24 to 36 hours, maintaining
a weak upper level trough across our region. Current satellite
imagery showing a good influx of mid and higher level clouds
moving through the district this evening, and are expected to
thin out on Sunday, as indicated by NAM 00Z cross section. ACARS
data showing a minimal marine layer inversion this evening, but
this inversion is expected to strengthen slightly overnight. This
in combination with a developing eddy circulation will likely
generate areas of low clouds and fog across coastal, valley, and
coastal slope locations. The marine layer depth is expected to be
around 4000 feet across the LA Basin, where there is the
potential for patchy drizzle.

Northerly gradients across the western Santa Ynez Range do pick
up slightly over the next few days so some gusty winds are
expected there during the afternoon and nighttime hours. Wind
gusts are expected to range between 25 and 40 mph tonight from
Gaviota to San Marcos Pass, then slightly stronger Sunday and
Monday when wind advisories may be needed for wind gusts of 30
to 45 mph across the western Santa Ynez mountains and adjacent
south coast.

.LONG TERM (WED-SAT)...06/125 PM.

The last of the upper lows circulating around the main upper low
over Oregon will come through late Tuesday into Wednesday, which
is a little faster than previous solutions. Model cluster analysis
indicates a high probability of this low taking an inside track
through interior CA before quickly shifting east Thursday. This
goes along fairly well the 12z deterministic solutions so it`s
unlikely going to have a significant impact locally. Some of the
ECMWF EPS solutions still have a little rain with it, mainly in
the mountain, though currently none of the GEFS solutions show any
precip. Main impact will be continued cool temperatures.

After Wednesday, model now are favoring a rapidly building and
positively tilted upper ridge into early the following week. This
is also supported by all the model clusters leading to higher than
usual confidence at the end of the 7 day forecast window. While
some of the NAEFS members also support some light to even moderate
offshore flow during this period, odds favor at least a light
onshore flow near the coast. In any case, several degrees of
warming are expected for the latter half of next week, likely
peaking next Saturday. Latest projections show warmer valleys have
a 30% chance of reaching the mid to upper 90s next weekend.
Coastal areas will likely be much closer to normal temperatures.

&&

.AVIATION...07/0031Z.

At 0015Z at KLAX, there was no marine layer nor sfc based
inversion.

Low to moderate confidence in TAFs. The currents forecast calls
for significantly more marine cloud coverage beginning late
tonight as warmer air aloft arrives to create a marine inversion.
There is a 40 to 50 percent chance that the current marine cloud
forecast is too expansive. Until later tonight, there is decent
confidence that conditions will be VFR across most of the area,
except near some mountains. There will also be some gusty winds
in the Antelope Valley through the period.

KLAX...Low to moderate confidence in TAF. MVFR cigs are likely
late tonight into Sunday morning, with a 20 percent chance of VFR
conditions through the period. A light easterly wind component is
expected late tonight into Sunday morning due to an eddy
circulation, but is expected to remain less than 8 knots.

KBUR...Fairly high confidence in TAF. MVFR cigs likely by early
Sunday morning, but 20 percent chance of IFR conditions and 20
percent chance of VFR conditions through the period.

&&

.MARINE...06/819 PM.

For the Outer Waters, moderate confidence in current forecast.
This afternoon through Tuesday, there is a 60-70% chance of SCA
level winds across PZZ673/676. There is a 40% chance of SCA level
gusts across PZZ670 Sunday afternoon/evening. Chances increase
for widespread SCA level winds, with a 20% chance for local gale
force winds Tuesday night through Thursday.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. High confidence in winds and seas
below SCA levels tonight. Sunday through Tuesday there is a
40-50% chance of SCA level winds in the afternoon and evening
hours. Chances increase (70%) for SCA level winds Wednesday and
Thursday.

For the Santa Barbara Channel there is moderate confidence in SCA
level winds over the western portion through late tonight. Sunday
through Tuesday, moderate confidence in SCA level winds in the
afternoons and evenings, with the strongest winds in the western
portion. Seas are expected to approach SCA level in the afternoons
and evenings, being the highest on Monday and Tuesday.

For the Inner Waters south of Point Dume, there is a 40-60% chance
of SCA level winds Sunday through Tuesday, especially over the
western portion during the afternoon/evening hours. Starting
today seas are expected to approach SCA level in the afternoons
and evenings, being the highest on Monday and Tuesday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Sunday for
      zones 650-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Gomberg/MW
AVIATION...Gomberg
MARINE...Smith
SYNOPSIS...MW/Smith

weather.gov/losangeles

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