453
FXUS63 KDMX 242339
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
639 PM CDT Fri Apr 24 2026

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

.KEY MESSAGES...

- Quiet and seasonally cooler through daytime Sunday.

- Thunderstorm chances return from Sunday night through Monday.
  Severe weather and heavy rain may be possible.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 117 PM CDT Fri Apr 24 2026

The cold front that surged through Iowa with severe
thunderstorms Thursday evening/night has passed well southeast
of the state. High pressure is building into the region behind
it, bringing sunny skies, north northwest breezes, and notably
cooler temperatures. Actually, the temperatures today are near
normal for the date, but are notably cooler because the last
several days have been 10-20 degrees above normal. In any event,
the high pressure area will provide clear, dry, cool, and quiet
weather for our service area through tonight and into Saturday.
Meanwhile, a large 500 MB gyre is parked over southern
Saskatchewan and Manitoba and will spin there through the
weekend. A shortwave impulse rounding the base of the gyre will
cross the Upper Midwest tonight into Saturday, generating rain
over parts of South Dakota, Nebraska, and Minnesota. This may
scrape our western and northwestern counties Saturday and
Saturday night, however, low-level dry air entrainment from the
departing surface high pressure area will mitigate this
possibility, as supported by forecast soundings around
Estherville and Carroll, and have limited POPs during this time
to slight change (<25%) in our far western counties. Saturday
and Sunday will also be slightly warmer as the high pressure
center moves off to our east, with highs both days ranging in
the upper 60s to lower 70s across the forecast area.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 117 PM CDT Fri Apr 24 2026

In the latter half of the coming weekend a broad 500 MB trough
will develop across the western U.S., extending down from the
Canadian gyre, with multiple shortwave troughs ejecting out of
it toward the Midwest and Iowa into early next week. This
synoptic set-up favors a more active weather pattern for us,
beginning late Sunday as the first such shortwave approaches
from the west southwest. A surface low pressure area will
develop in response to the approaching wave somewhere near the
Oklahoma Panhandle on Sunday afternoon, then pivot up to around
northeastern Kansas by early Monday morning. Ahead of the
surface low, and beneath the broad area of strong lift in the
leading flank of the approaching mid-level trough, a pronounced
nocturnal low-level jet will develop Sunday night mainly over
the western half of Iowa. The NAM projects 850 MB winds to
increase from around 25 KT at sunset Sunday evening to 50-60 KT
after midnight Sunday night. These factors will contribute to
the development of a large area of showers and thunderstorms,
initially somewhere around eastern Nebraska and northern Kansas,
then surging northeastward across Iowa overnight. Forecast PoPs
are near 100% in our area, and while instability is fairly
limited (with MUCAPEs of perhaps 500-1000 J/kg at best),
strengthening flow and shear profiles associated with the LLJ
may support some threat of severe weather Sunday night. Hail
will be possible, but mitigated by persistent moisture transport
resulting in a nearly saturated column. Gusty winds would
appear to be the higher threat given the strength of the low-
level flow, but that is contingent on convection being surface-
based overnight, or an organized cold pool developing within the
large mess of convective elements. Given these various factors,
the Marginal Risk outlined by the SPC is appropriate for our
area Sunday night.

On Monday the leading 500 MB shortwave will move overhead and
deepen a bit, possibly closing off somewhere near the IA/MN
border. This evolution will induce the High Plains surface low
to pivot northeastward and deepen over Iowa, with a cold
front/dryline trailing southward into Missouri. A dry slot will
develop behind the departing overnight/morning convection and
ahead of the trailing boundary, and depending on the degree of
clearing/destabilization that can occur within the dry slot,
robust convective development is likely along and just ahead of
the trailing boundary Monday afternoon to evening. Given the
presence of strong forcing for ascent and impressive deep-layer
shear magnitude, any instability will allow for a threat of
severe weather during this time, though the details of which
hazards may be most likely are still unclear. The other primary
uncertainty factor is the location of the surface low, trailing
boundary, and dry slot. Resolution of these features varies from
model to model and run to run. The 12Z NAM has come in slower
with the progression of the parent system, resulting in the
center of the surface low being near Estherville at 00Z Tuesday
(that is, Monday evening) and storms firing right down across
central Iowa and into northern Missouri. The 06Z GFS, meanwhile,
locates the center of the low near Waukon in far northeast Iowa
at 00Z Tuesday, with the storms firing east of our area in far
southeastern Iowa. Given the potential magnitude of the overall
severe weather threat, but large uncertainty in mode and
location, the SPC has outlined a relatively large risk area from
central Iowa eastward to around Chicago and southward into the
lower Mississippi River region. These potential threats will be
refined in the coming days as confidence in details gradually
increases.

From Monday night through the remainder of next week the 500 MB
pattern will become more broadly cyclonic, with generally west
northwesterly steering flow over our region and more subtle
shortwaves moving through at intervals. This general pattern
will support periodic rain chances but with an overall lower
severe weather threat, along with a continuation of relatively
cooler weather as daily highs generally range in the 60s or so.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 639 PM CDT Fri Apr 24 2026

VFR conditions will prevail through the TAF period. Winds shift
from out of the north to northeast this evening to out of the
southeast by Saturday morning. Light, spotty showers are
possible in far northern Iowa on Saturday, however dry air will
prevent much development and thus have kept from the KMCW TAF at
this time.

&&

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

&&

$$

SHORT TERM...Lee
LONG TERM...Lee
AVIATION...Hagenhoff