Grimes, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

427
FXUS63 KDMX 251724
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1224 PM CDT Sat Apr 25 2026

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- A few showers and non-severe thunderstorms possible far west
  late today and tonight.

- Thunderstorm chances increase from west to east Sunday and
  Sunday night.

- Monitoring potential for a significant severe weather event on
  Monday.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 247 AM CDT Sat Apr 25 2026

A mostly quiet early morning across Iowa. A ribbon of mid-leve theta-
e advection is leading to a region of showers and a few
thunderstorms from southeast South Dakota and into north central
Nebraska. Big picture wise, a large upper level low pressure remains
over Saskatchewan today. A robust upper level system off the west
coast of California, will begin to move east today and combined with
the northern upper low, will begin to tilt the upper level flow more
southwesterly. That flow will begin to increase the moisture
transport into the state and gradually eroding the drier air
currently in place in Iowa and will lead to increasing precipitation
chances tonight and Sunday.

Expect mostly dry conditions today as low level easterly flow
develops from near the surface up to around 5 kft. The one feature
to watch with this easterly flow is the stratus that is currently
over eastern Wisconsin and Lake Michigan. The steering flow for this
stratus will keep pointing south for the next several hours before
turning more northeast then east as that easterly flow develops this
morning. That may bring some of this stratus into parts of eastern
Iowa today. Mid to high level cloud cover will also increase over
parts of western and northwest Iowa today as the theta-e advection
aloft arrives through the day. CAMs and other guidance are
suggesting a few thunderstorms will be translating east this
afternoon and may reach parts of western Iowa later afternoon and
into this evening. At this time, it appears this activity will begin
to outrun the feeding instability, leading to a weakening in that
activity as it moves towards the western DMX CWA. A few
thunderstorms could occur overnight as limited instability
develops.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 247 AM CDT Sat Apr 25 2026

Lee side cyclogenesis will occur over southeast Colorado on Sunday
as the California upper level system translates eastward. Waves
of theta-e advection lifting into Iowa will intensify as the
low deepens and moves into western Kansas. This will lead to
increasing thunderstorms chances, especially later in the
afternoon and in particular overnight. A few storms with large
hail are possible.

The western upper level system will lift into Nebraska and southeast
South Dakota on Monday while surface low pressure deepens as it
lifts north/northeast across Iowa from late morning and through the
afternoon. This is a setup that has the potential for significant
severe weather across parts of the state. Continue to monitor the
strong tornado potential with a large amount of low level shear and
helicity within the 0-1 km layer and increase streamwise vorticity
ingestion potential for any organized supercell storms. A few spot
checks over parts of central and southern Iowa suggest the 0-1 km
streamwise vorticity values may top 0.03, which is quite high. In
addition the upper level jet will be cutting across the warm sector,
which would also support strong tornado potential. Stay tuned,
there remains some uncertainty on the exact track this system
takes. SPC now has an Enhanced risk for severe weather Monday
with a 45% hatched areas over parts of Iowa.

No significant weather is anticipated for the rest of next week
as severe iterations of high pressure remain the primary
influence. High temperatures in the 50s and 60s will be near to
slightly below seasonal averages. Perhaps a period or two of
frost may occur.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1224 PM CDT Sat Apr 25 2026

VFR conditions will prevail through the TAF period, with a
gradual increase in high level clouds this evening and tonight.
There is an area of low ceilings around FL030-035 over eastern
Nebraska that is attempting to creep eastward into Iowa, but it
is encountering dry easterly flow that is eroding its leading
edge and the probability is low that it will be able to reach
DSM. In addition, isolated SHRA/TSRA will be possible tonight
into Sunday, but probability of impact at any terminal is too
low for TAF mention at this time.

&&

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

&&

$$

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