579
FXUS63 KDMX 040831
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
331 AM CDT Sat May 4 2024

.KEY MESSAGES...

- Thunderstorms passing across Iowa early this morning into
  early afternoon with low end wind and hail risk.

- Additional strong to severe storms on Monday evening into
  Tuesday

&&

.DISCUSSION...
Issued at 331 AM CDT Sat May 4 2024

A surface low has ejected across the central plains and towards the
midwest through the overnight. Convection has ridden the surface
warm front into the area with storms persisting thanks to low-level
jet reinforcement. By 3 AM storms were entering western parts of the
area, but have lost some steam thanks to weak instability into Iowa
as the primary axis falls short of the area. This line of storms
will continue progress across the area through the morning,
exiting east in the early afternoon. MLCAPE through today
remains around 500 J/kg with rather modest lapse rates, though
deep layer (0-6 and 1-6 km) shear within sounding comes in at
40-50 kts. Given the parameter space, expect some small hail and
wind risk with storms, however the severe threat remains on the
lowers side into the afternoon.

At the same time, hydro concerns remain in the back of our minds.
Given recent heavy rains in recent days, a few areas are more
sensitive (rivers in northern Iowa in minor flood and south-central
Iowa which saw flash flooding earlier in the week). The good news
here is that storms are fairly progressive which will mitigate most
issues. HREF LPMM places a widespread 0.75-1.0" across the area with
a few pockets of 1.5+" possible.

Sunday will bring a welcome reprieve in the active period with weak
ridging into the area behind the departing low. This is short-lived
as the next system will be on our doorstep, swinging across the
Rockies. By Monday will will move across the plains. In Iowa this
will make for a breezy afternoon as the pressure gradient tightens
ahead of the system. Recent model runs have slowed the progression
of the system, lifting it across Iowa later Monday evening and into
the overnight before exiting on Tuesday. A plume of instability
cuts across the area with 1500+ J/kg MLCAPE and deep layer
shear exceeding 40 kts. Model soundings indicate tall skinny
CAPE profile with sweeping hodographs through the lowest 2 km.
With 0-1 km SRH exceeding 200 m2/s2, tornadic activity is
something to be aware of, in addition to the hail and wind
concerns.

The week remains active with another system on Wednesday/Thursday.
Details on this will be forthcoming as this system is closely
associated with the Monday/Tuesday system and will be heavily
influenced by it.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1205 AM CDT Sat May 4 2024

MVFR to IFR cigs to move in with rain and thunderstorms. Have
added thunder mentions to to all terminals as confidence is
increasing in thunderstorms for even KMCW and KALO. Highest
confidence at KFOD, KDSM and KOTM with vsby reductions and gusty
winds also possible for KFOD and KDSM in the next 6 hours. Will
continue to evaluate trends. Gusty northwest winds to follow
departing rain, easing at sunset.

&&

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

&&

$$

DISCUSSION...Hagenhoff
AVIATION...Jimenez