893
FXUS63 KDMX 281100
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
600 AM CDT Sun Apr 28 2024

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- More showers and storms today. A few may be strong to severe,
  but the threat looks highly conditional at this time.

- Storm chances return Tuesday along with the potential for
  strong to severe storms. Forecast trending wetter through the
  middle of the week.

&&

.DISCUSSION...
Issued at 252 AM CDT Sun Apr 28 2024

Shower and storm chances persist again today as an upper low
slowly moves toward the northern Plains. While the primary
moisture/instability axis will remain well south, some moisture
is pulled back westward toward the low and will help support
scattered to widespread precip. Hires guidance suggests the
greatest coverage occurs this afternoon into the early evening
hours. Severe threat today looks highly conditional as
instability looks limited due to precip/cloud cover. Deeper
convection that develops this afternoon over eastern
KS/northern MO could dribble into southern Iowa and pose a
threat for hail and gusty winds before weakening. Still cannot
rule out potential for a few weak tornadoes, although again
instability is a significant limiting factor. Ambient vorticity
increases as upper and sfc lows both pass near or west of the
forecast area. Sfc pressure field generally weakens and winds
try to veer from se to sw through the day. It will likely take
appreciable clearing and the development of more robust low
level instability to generate enough stretching to support a
quick spin up. Will need to monitor trends through the day, but
at this time the threat looks low.

Conditions dry out Monday as deep layer subsidence increases behind
the departing upper low. Moisture wrapping around the backside of
the system will promote broken to overcast cloud cover especially
early in the day, and will help hold highs in the upper 50s north to
mid 60s south.

Forecast activity picks right back up through the middle to latter
portions of the week as a series of shortwaves follow an upper
jet streak traversing the central Rockies into the local region.
Moisture returns northward on Tuesday ahead of an approaching
surface front. Precip chances ramp up by mid to late day as
showers and storms develop within the vicinity of the front.
SBCAPE builds to near 1000-2000 J/kg and effective shear ~40-50
kts, which would be sufficient to support more organized strong
to severe storm activity. This idea is backed by the CSU ML
output that paints lower end severe probs over the cwa. Front
stalls out just south of the area and is lifted back northward
on Wednesday as models have trended more progressive with
successive waves. The baroclinic zone serves as the general
focus for additional rounds of showers and storms by late
Wednesday through Thursday. While widespread heavy rain does not
likely, there is a signal in the models for a potential axis of
heavier QPF amounts, likely associated with training deeper
convection. Precip potential becomes more uncertain as a deeper
upper low pulls out of the central Rockies late in the week.
Euro camp is more progressive and considerably drier by the end
of the week, whereas the more sluggish GFS/GEFS solutions would
favor more precip chances into Friday.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 559 AM CDT Sun Apr 28 2024

A mixed bag of categorical restrictions are observed over the area
early this morning due to variable cigs and shra activity. Expecting
MVFR to IFR cigs to become more widespread by mid to late morning in
concert with the redevelopment of more shower and storms. A brief
period of improvement after 22z is forecast to occur as dry air
scours out the lowest cigs over much of southern and into central
Iowa. Uncertain if the cig improvements reach as far north as KMCW,
so that particular terminal forecast was left at MVFR. Stratus is
reinforced with lower MVFR to IFR cigs gradually fill back in
between 06z and the end of the TAF period.

&&

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

&&

$$

DISCUSSION...Martin
AVIATION...Martin
HYDROLOGY...Zogg