687
FXUS63 KDMX 031827
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
127 PM CDT Sun May 3 2026

.KEY MESSAGES...

- Breezy and dry this afternoon, with winds diminishing by this
  evening.

- Milder temperatures on Monday, but with a cold front pushing
  through in the afternoon and evening. A few strong to severe
  thunderstorms will be possible along the front late in the day
  across the southeastern half of Iowa.

- Cooler weather from Tuesday into Thursday, with another
  frost/freeze possible in parts of Iowa Tuesday night.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 126 PM CDT Sun May 3 2026

A weak surface high pressure area is building into the area from
today, heralded by a wind shift that has passed across most of
our service area. Behind this boundary there is little sensible
temperature difference, but winds are turning to northwest and
increasing to 15-25 MPH with gusts of 25-35 MPH. However, these
higher winds will only last for a few hours, as the combination
of the high building in and diurnally diminishing low-level
mixing will cause winds to go light and variable by around
sunset, then come around to south southwest and remain light
overnight. Meanwhile, temperatures have risen into the mid-60s
to lower 70s this afternoon beneath mostly sunny skies, and with
dewpoints remaining in the mid-30s to lower 40s. This has made
for a glorious spring day for most outdoor interests. The dry
and quiet weather will continue tonight as temperatures fall
into the mid/upper 40s, prevented from falling much further by
the light but organized south southwest breezes overnight.

By Monday morning a 500 MB shortwave trough will be moving
across North Dakota and Minnesota, pushing a cold front
southward toward Iowa. The front is expected to reach our
northwestern areas near Estherville and Algona around noon or
just after, eventually reaching our southeastern areas near
Ottumwa and Centerville by Monday evening. The broadly cyclonic
flow spreading aloft on the southern periphery of the passing
shortwave will initially bring modest and nebulous forcing for
ascent. However, late in the day and into the evening, slightly
better forcing combined with diurnal destabilization will
support gradually increasing shower and thunderstorm chances.
Initially, it is likely that the advancing surface front will
provide a focus mechanism for the first storms to develop in the
late afternoon, likely in our eastern to southeastern counties
where the boundary is expected to lie and where the preceding
capping inversion will be weakest/erode earliest. This initial
round of showers and storms should exit relatively quickly to
our southeast on Monday evening, however, a subtle secondary
shortwave moving overhead Monday night may support lingering
overnight rain along the 925-850 MB frontal zone, if low-level
dry air can be sufficiently overcome, resulting in lingering
light rain chances over the southern 1/2 or 2/3 of our forecast
area Monday night, exiting to the south on Tuesday. Behind the
initial surface front, instability and moisture will be limited
and severe weather is not anticipated with the later activity.
However, during the initial round of storms along the surface
boundary late Monday afternoon and evening, surface-based CAPE
of around 1000-1500 J/kg is forecast, along with deep-layer (0-6
KM) bulk shear of around 30-40 KT. Low-level moisture will be
lacking with dewpoints likely only in the 40s, however, forecast
soundings indicate steep mid-level lapse rates and good low-
level mixing supporting a modest threat of hail and gusty winds
from any stronger updrafts. The SPC has outlined about the
southeastern half of Iowa with a Marginal Risk, which is
appropriate for this scenario.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 126 PM CDT Sun May 3 2026

Any lingering rain will clear out of southern Iowa on Tuesday
as cool and dry air continues to filter in from the north.
Temperatures will be notably lower behind the cold front, with
daily highs only in the mid to upper 50s both Tuesday and
Wednesday. Cyclonic 500 MB flow will persist aloft during this
time, but any thought of rain chances is mitigated by the lack
of available moisture or instability. Meanwhile, Tuesday
night/Wednesday morning lows will fall into the 30s across much
of Iowa once again, with near-freezing temperatures in the
north, prompting another round of frost/freeze concerns at
least in some areas.

A couple of more pronounced 500 MB troughs will move over later
this week, from around Thursday onward, providing a return of
low (20- 30%) PoPs at times, but no significant precipitation or
hazardous weather is foreseen. Meanwhile, the surface pattern
will become more erratic and diffuse in general, supporting a
slow moderation of temperatures as highs return to the 60s on
Thursday and Friday, and possibly some 70s by next weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1210 PM CDT Sun May 3 2026

VFR conditions are forecast through the 18Z TAF period. Gusty
northwest winds are forecast for the next several hours, after
which they will diminish, go light and variable for a period
this evening into tonight, then come around to SSW by Monday
morning. No precipitation or obscurations are anticipated
during this time.

&&

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

&&

$$

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