657
FXUS63 KDMX 092312
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
612 PM CDT Sat May 9 2026

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

.KEY MESSAGES...

- Light rain/sprinkles near the Iowa/Missouri border possible
  tonight.

- Low temperatures approach the mid 30s tonight and low 30s
  tomorrow night. Frost development and/or temperatures near
  freezing could damage sensitive plants.

- Warmer temperatures return to start the week. Shower and
  thunderstorm chances (35 to 45%) late Monday night into
  Tuesday, mainly over northeast Iowa. A few stronger storms
  could develop, but severe weather potential is low and
  conditional at this time.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 252 PM CDT Sat May 9 2026

The surface boundary that passed through the area this morning has
started to usher in a cooler air mass over Iowa today, most
noticeably across northern Iowa where temperatures are only in the
low 60s. Farther into central and southern Iowa, temperatures have
reached the mid 70s, but likely won`t warm much more as typical
diurnal processes wrestle with the cold air advection (CAA) regime.
Another byproduct of the CAA are the breezy north northwesterly
winds ongoing over much of Iowa today, with sustained winds around
15 to 20 mph and gusts of 25 to 35 mph. Light showers trailed the
surface boundary through the morning, roughly co-located with the
850 mb boundary aloft, resulting in some sprinkles/light rain
through northern and north central Iowa. However, these have since
dissipated as they`ve encountered the drier air mass farther south.
Re-development was expected along this boundary later today and into
tonight as a weak lobe of energy tracked eastward out of Nebraska
into southern Iowa, but recent trends imply this will now stay south
of the state. Weak scattered showers can be seen upstream on MRMS
output, but these are on trajectory to stay just south of Iowa.
Likewise, the weak swath of instability that was scraping the
Iowa/Missouri border yesterday is now well south into north
central Missouri in today`s guidance. Therefore, signs are
pointing towards a dry forecast in Iowa tonight, although have
maintained the sprinkle mention along the southern border should
the elevated boundary find enough moisture to squeeze out a
hydrometeor or two.

The cooler air mass and surface high pressure filling in today will
bring diminishing winds and clearer skies overnight tonight.
Temperatures are forecast to fall into the mid 30s across the north
to mid 40s across the south, although radiational cooling early
Sunday morning may cause these to fall even further in areas where
skies clear. This introduces some concern for temperatures
approaching the low 30s, but have held off on frost headlines given
the upper 20 dewpoints and potential for upper level clouds/cirrus
to move through.

This air mass and high pressure sticks around through the day on
Sunday, keeping temperatures mild in the 60s to near 70 with lighter
winds than today, albeit still breezy in northern Iowa. This should
make for a pleasant day to celebrate all the great mothers out
there. Winds then go light again Sunday night into Monday morning,
bringing yet another cool May night in Iowa. Mid-level clouds in
place over central and southern Iowa will prevent the floor falling
out from under temperatures Monday morning, but northern Iowa may
not be so lucky as skies clear out overnight. Temperatures will
likely dip into the low 30s, approaching or falling below freezing
in far northern Iowa. Dewpoints will be in the mid to upper 20s,
suggesting cool, elevated surfaces and/or vegetation could see some
light frost development. With temperatures nearing freezing, frost
or freeze headlines may be needed tomorrow night.

The upper level pattern transitions a bit to begin the work week, as
the 500 mb low over the Hudson Bay begins to break up and ridging
builds eastward. This will allow warmer temperatures to the west to
build back into Iowa, boosting highs back into the 70s and then 80s
on Monday and Tuesday. Before the upper ridging can fully build in,
a more prominent shortwave wave will dive southward into North
Dakota and Minnesota from Monday night into Tuesday, just to the
north of Iowa. Forcing coincident with this wave is expect to
bring shower and thunderstorm chances back to the upper midwest
through this period, although our forecast are remains partially
displaced to the southwest of much of this activity according
to deterministic guidance. This puts the greatest precipitation
potential over northeastern Iowa, only just scraping our
northeastern forecast area. That said, the wave will drag a
boundary southwest to northeast oriented boundary behind it,
affecting all of our forecast area. Guidance does try to kick
off light QPF along this boundary through the morning and into
mid-day Tuesday, before departing the area Tuesday evening, but
the signal is far from robust. Timing of the wave will be
important to watch, as a slower progression would allow for more
warming out ahead of the front, resulting in more instability.
This scenario was being alluded to in yesterday`s guidance,
although it has sped up slightly again in today`s cadre of
models. Even in the slower, more unstable solutions (ie the GFS)
parcels are still combating a mid-level warm nose/capping.
Shower and thunderstorm chances remain in the forecast for this
period, but generally favor areas in northeastern Iowa given the
weak signal for activity farther south and east in the more
capped environment. At this point, the severe weather threat
looks low, but conditional on a more unstable and less capped
environment preceding the frontal passage. The more widely
experienced feature on Tuesday will be windy conditions
occurring along and behind the front, with the strongest winds
being over northern Iowa Tuesday afternoon where gusts up to 45
mph are forecast.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Issued at 252 PM CDT Sat May 9 2026

The Monday night into Tuesday wave departs eastward Tuesday night
into Wednesday, allowing cooler air to briefly fill in behind it.
With no more troughs blocking the broad scale pattern, 500 mb
ridging will build eastward into Iowa through the remainder of the
week. A warming trend will then begin through the end of the work
week, and potentially into the weekend, as highs climb into the 80s
Thursday and Friday. NBM guidance would suggest we could even be
approaching highs in the 90s into next weekend, although
deterministic guidance does add some uncertainty to that as the
pattern also becomes a bit more agitated on the backside of the
ridge, bringing in multiple shortwaves and more chances for
showers/storms. Therefore, the main takeaway at this time frame is a
warming trend through the second half of this week, and
potentially a more active period into next weekend. &&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1220 PM CDT Sat May 9 2026

VFR conditions prevail through the period. Light showers/sprinkles
are passing through the area today, but should produce minimal
impacts. Northwest to northerly winds continue this afternoon,
sustained around 15 kts with gusts over 25 kts possible at
times. Winds will become light and somewhat variable tonight,
although the prevailing direction will be out of the north.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 611PM CDT Sat May 9 2026

VFR conditions will prevail through the end of this TAF period.
Skies have started to clear for terminals north of DSM at the
start of this TAF period. Clouds will continue to clear with
winds becoming light and variable into the overnight hours. A
cloud deck is expected to move in from the north early
afternoon for ALO and MCW terminals ahead of a boundary but will
stay VRF during that time. Wind gusts will increase out of the
NW towards the end of the period with a few gusts reaching 20-25
mph at ALO and MCW.

&&

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

&&

$$

SHORT TERM...Dodson
LONG TERM...Dodson
AVIATION...Ansorge/TDR