Grimes, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

033
FXUS63 KDMX 241131
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
531 AM CST Sat Jan 24 2026

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

.KEY MESSAGES...

- Light snow across southern Iowa today. Accumulation of 1-2".

- Reinforcing shot of cold air Sunday night into Monday morning will
bring wind chills back down into the -10s to -20s.

- Remaining cold through the upcoming week.

&&

.UPDATE...
Issued at 235 AM CST Sat Jan 24 2026

High pressure has allowed for quiet conditions across Iowa
early this morning. Temperatures has fallen into the -5 to -15
degree range so far, though with lighter winds the wind chill
has marginally improved over those seen on Friday. A handful of
sites across the area remain at -20 to -25 but continue to
improve, and the Cold Weather Advisory will expire as scheduled
at 3 am. Meanwhile, high and mid level clouds continue to stream
into the area, associated with the incoming winter storms set
to impact much of the southern US through this weekend. Light
snow has begun at Lamoni and Creston early this morning, though
no accumulation is evident on area webcams. Moisture will
increase across central and southern Iowa into this afternoon.
Meanwhile, the arctic high will maintain very dry air central
and north. The battle between the incoming moisture and dry air
will impact the expanse of any accumulating snowfall today.
Model cross sections indicate that relative humidity remains
around 80-85% from around the I-80 corridor and south with brief
periods of mid level saturation increasing to 90+% in the
afternoon. Soundings maintain a deep isothermal layer through
the dendritic growth zone. Omega is modest with around -5 ubar
in southern Iowa this afternoon. Putting it all together, while
there is sufficient moisture for snow production and a deep
dendritic growth zone, the lack of better saturation and weak
lift will prevent higher snow totals. An inch or two of snow
remains possible across southern Iowa. While light snow may make
it as far north as the I-80 corridor, any notable accumulation
that far north is unlikely. Many CAMs previously maintained
better accumulations (>1") all the way up to the I-80 corridor
in earlier runs, however the 06z runs have backed off and seem
to better recognize the impacts the dry air will have.

A reinforcing shot of arctic air arrives Sunday night into
Monday, resulting in another morning with wind chill values in
the -10s to -20s. Parts of northern Iowa may need another Cold
Weather Advisory. The cold air lasts through the upcoming week
with weak shortwaves passing across the area to bring
reinforcing arctic air and periods of light snow.

&&

.DISCUSSION...
Issued at 251 PM CST Fri Jan 23 2026

Arctic high pressure is ridged into Iowa this afternoon with the
center to the north over west central Minnesota. Temperatures at 2
pm remain below zero for the entire area which is impressive over
the snow free areas over central and southern Iowa. The coldest
temperatures are with the light snow cover over northern Iowa with
reading of 7 to 11 below zero. High level clouds have been streaming
over the southern half of the state today and the resultant
filtering of solar energy is in part responsible for temperatures
remaining below zero over the snow free areas.

A more organized mid level cloud layer around 8 kft extends from
northern Missouri into central Nebraska. That layer is closely
linked with with moisture and theta-e advection around 750 mb. That
cloud cover has been mostly stagnant so far today with little
progress northeast but it will begin to make progress later this
afternoon and tonight. Will be using this cloud deck as a proxy for
the low temperature forecast tonight and have leaned closer to the
NBM 75th percentile over the southwest to near to slightly below the
NBM 50th northeast. Dew points over northeast Iowa are in the low
20s below zero over northeast Iowa. The high level cloudiness
shouldn`t have much impact of any radiational release overnight. The
high pressure center will move southeast and winds will diminish to
less than 5 mph over the northeast. With current temperatures near
10 below at Waterloo and Mason City and considering the dew points
and some light snow pack, a run for 20 below zero is possible. With
the winds becoming light, wind chill values will rise just above
advisory criteria overnight and have kept the end of the advisory at
3 am CST.

Light snow chances over southern Iowa are the other forecast
challenge this forecast cycle. Numerous model guidance are trying to
bring at least light QPF south of Interstate 80. Several things to
consider here also. First, any gulf moisture is cutoff well to the
south of Iowa. There is good mid-level moisture transport
originating from the Pacific and that extends up into southern Iowa.
This is what is moving the mid-level cloudiness over the area
tonight. There is light snow and cloud bases near 3 kft over western
Kansas and far western Nebraska. This moisture will try to move east
towards Iowa, which will have the Arctic high pressure nearby.
Typically the dry air from these very dry/Arctic high pressure
systems wins out and results in less precipitation that model
guidance. Model RH cross-sections across Iowa are a less than
impressive 75-85 percent. Typically look for 75 percent for ice
nucleation and even if that is achieved, the snow flake microphysics
process will be impacted, likely resulting in smaller flake dynamics
that may evaporate more easily and certainly will result in a low
snow to liquid ratio. The other consideration is that with such a
cold air mass, it does not take much moisture to have some
saturation but still the lack of low level moisture advection should
be a big limiting factor here. Therefore, have limited snow chances
more south and backed off snow amounts but did keep up to 2 inches
possible near the Missouri border. At this point, no headlines are
expected, especially with the light wind.

Beyond that, it still looks to be a cold end of January with several
surges of cold air southward with a mostly predominant northern flow
from central Canada to Iowa. There should be a could light snow
chances embedded in the forecast and with the greatest chance
projected around Wednesday, but that is a ways out trying to track
temporal and spatial placement of and short waves.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 531 AM CST Sat Jan 24 2026

Light snow is falling across southwest into central Iowa early
this morning. Northern TAFs will not see snow and have kept to a
single line at KFOD/KMCW/KALO. Snow is further north than
anticipated this morning with MVFR visibility at KDSM already.
Anticipate that saturation will waver through the day,
resulting in on and off periods of light snow. Have attempted to
target the most likely windows this morning and again in the
afternoon with a prob30 group, however confidence in precise
timing is not high and adjustments are likely. Snow has not yet
made it to KOTM but expect it to arrive by midday. More
persistent snow is expected there along with light accumulation.

&&

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

&&

$$

UPDATE...Hagenhoff
DISCUSSION...Donavon
AVIATION...Hagenhoff