455
FXUS63 KDMX 160506
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1206 AM CDT Thu May 16 2024

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

.KEY MESSAGES...

- Showers and storm chances increase this evening into the overnight.
  Highest chances north. Severe threat low.

- Active pattern continues this weekend into early next week.
  Threat for severe weather and heavy rainfall may develop
  Sunday night and again Monday night into Tuesday, although
  specific details remain uncertain at this time.

&&

.DISCUSSION...
Issued at 200 PM CDT Wed May 15 2024

19z GOES water vapor imagery shows an active split-flow pattern over
the conus with several embedded lower amplitude waves. One such
shortwave was noted crossing the northern Plains and will serve as
the impetus for precip chances through the next 24 hours. At the
surface a weak low pressure center was over eastern SD with a
surface boundary extending south toward the MO River valley. Thermal
forcing and meager moisture return ahead of the front will phase
with the increasing kinematic ascent with the approaching upper
wave to produce more scattered to widespread shower/storm
activity later this afternoon into the evening over western
Iowa, then pushing eastward late this evening and overnight.
Highest chances (>50%) for rain will reside over the northern
half of the cwa. The shear and instability parameter space is
not overly supportive of organized strong to severe convection,
but some sporadic small hail or gusty winds cannot be ruled
out.

Frontal boundary progression is sluggish and will only be over
eastern Iowa by Thursday morning. Lingering showers/storms are
possible into Thursday morning, but most hi-res guidance suggests
afternoon redevelopment will occur east of the cwa. Most
locations should be dry for the majority of the day with temps
reaching into the 70s to near 80. GFS still wants to graze
southern Iowa with light rain Friday as it brings an upper low
much further north than other guidance. This is an outlier
compared to most ensemble guidance and the NBM continues to
trend in a dry direction.

An active forecast continues over the weekend and into early next
week as the synoptic pattern aloft gradually transitions to mean
western troughing and southwesterly flow. Storms are possible as a
frontal boundary pushes through Saturday, however much more
organized robust chances likely evolve early next week as the Gulf
opens up and deeper moisture streams northward. Details at that time
range are still nebulous considering the typical model variances and
likelihood for mesoscale processes to drive convective evolution,
however models are keying on Sunday night and then again Monday
night into Tuesday for the most probable windows. A threat for
severe storms and heavy rainfall may develop, but will be more
acutely determined in the days ahead.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1200 AM CDT Thu May 16 2024

VFR conditions prevail across much of central Iowa with a few
MVFR conditions co-located with the locations of showers/storms.
First round has moved through the area with the second round
moving into northwest Iowa bringing some shower and storms into
areas north. Vicinity of storms only looks to impact KFOD early
in the period with otherwise shower mentions at northern sites
overnight and southern sites (KOTM) early Friday morning.
Guidance continues to suggest MVFR, locally IFR conditions to
move through the area early Friday morning but kept towards
higher end of guidance with overall probabilities for IFR fairly
low (isolated ~30-40%), but updates may be needed if conditions
exceed current expectations.

&&

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

&&

$$

DISCUSSION...Martin
AVIATION...KCM