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000
FXUS63 KDMX 180450
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1150 PM CDT Wed Apr 17 2024

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- Rain to move in tonight with thunderstorms southwest. Some
  could be strong to severe with gusty winds and hail.

- Rain exits Thursday afternoon with below average temperatures
  behind for the remainder of the week. Below freezing lows
  likely (>75%) this weekend.

- Next precipitation window early next week.

&&

.DISCUSSION...
Issued at 251 PM CDT Wed Apr 17 2024

The low pressure that impacted the state continues to lift to the
northeast this afternoon. Diurnal mixing has eliminated some of the
stratus in the southwest half of the state, allowing temperatures
there to rise into the 60s. The clear skies and fair weather will be
short-lived.

Morning upper air analysis showed a wave in the High Plains as well
as an area of low pressure over the Texas panhandle. This low will
lift northeastward overnight and bring with it moisture from the
Gulf. The wave from the west will be accompanied by Pacific
moisture. The two areas of moisture will be out of phase with each
other, but both will bring rain to the state starting tonight
lasting into Thursday. The Pacific moisture will impact all but the
bottom third of the state and will depart with the synoptic wave
Thursday afternoon.

The southern stream of moisture will precipitate along an fgen band
that spans into southwest Iowa this evening. The instability
axis will span into this region as well, but with higher values
remaining in MO. The base of the trough with an intensifying
midlevel jet will center over the area tonight with some
diffluence on the exiting half. Paired with the front mentioned
earlier, this is a favorable setup to produce mesoscale gravity
waves (MGW). CAMs are keying in on evening convection positioned
just behind the front and are producing spots of 40kt+ wind
gusts with the MCS as it interacts with the MGW and transfers
winds aloft towards the surface. Soundings support this
possibility with time series cross sections with pockets of
large positive omega reaching the surface. While most of these
storms storms will not organize until they sink into MO, cannot
rule out gusty winds in Iowa along. Some hail will be possible
given the available MUCAPE.

Beyond Thursday, broad troughing will deepen over the region and
keep a colder airmass overhead, keeping temperatures in the 50s for
the rest of the week. Lows will be in the low 30s and even 20s in
spots in the weekend which will warrant frost/freeze headlines. High
pressure will keep precipitation away until a shortwave arrives
early next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1150 PM CDT Wed Apr 17 2024

Light showers are moving from Nebraska into Iowa and will affect
the terminals overnight, with a few thunderstorms likely in
southern Iowa including at OTM during the early morning hours
Thursday. Have gone with prevailing SHRA for much of the night
but visibility restrictions will be generally light/MVFR and
intermittent. Meanwhile, a large area of low stratus clouds will
move through with the rain and produce prevailing low ceilings
below FL020 for much of the night/morning. There is potential
for several hours of IFR within this time, however confidence is
not high enough to include in the TAFs at this time. Amendments
are likely overnight based on radar/observational trends.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

DISCUSSION...Jimenez
AVIATION...Lee