textproduct: Des Moines

KEY MESSAGES

- Swath of accumulating snow possible Wednesday afternoon into the evening. Increasing potential for pockets of 2 to 4 inch amounts.

- Snow may switch over to a brief freezing drizzle/rain late Wednesday night into early Thursday morning.

- Temperatures warming again Thursday and Friday. More precipitation possible through the weekend and into next week.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 257 PM CST Tue Feb 24 2026

Our warmer southerly air has brought temperatures into the mid 50s in our snow free areas over southern Iowa, while areas with snowpack have generally only warmed into the mid 30s as of 2 PM. The shortwave passing to our north responsible for freezing rain and snow in Minnesota is dragging a "cold" front through the area which will flip flow to a north northwesterly direction through the evening. While this is a cold front on a broad scale (colder air mass moving into a warmer air mass) surface temperatures are actually warmer behind the front due to the snowpack holding temperatures down over Iowa. In fact, temperatures in snow free areas in northern Iowa are actually warming behind the "cold" front, as the prevailing wind direction is no longer advecting the colder air over the snow up from the south and instead advecting the warmer air from snow free areas to the northwest. Likewise, better mixing is being realized behind the front and mixing warmer temperatures down to the surface, as opposed to the inversion in place ahead of the front and over the snow. This discrepancy is only present at the surface, however, and temperatures aloft will be cooling behind the front tonight. This cold air advection regime will result in cooler highs on Wednesday over much of the area. Have continued to err on the lower end of guidance for lows tonight and highs tomorrow in areas with snow on the ground.

The main focus of today's forecast has been the quick-moving clipper system that will drop from northwest to southeast through central Iowa tomorrow afternoon into early Thursday morning. This system remains a challenge to pin down, particularly in regards to total snowfall amounts, as the 12z runs of high resolution models have only increased the dispersion of solutions. First, looking at the system conceptually, our main sources of lift will be isentropic lift and mid-level frontogenesis as warmer air overruns the cooler air filling in on the north side of a low passing through eastern Nebraska and Kansas, into northwestern Missouri. This lift looks fairly healthy in soundings and cross sections, with roughly 10 to 20 microbars of vertical ascent present along the fgen band. As discussed in previous discussions, the placement of the surface low will cut off the low-level moisture from the area, meaning the column will need to take advantage of pacific stream moisture in the mid- to upper- levels and saturate from the top down. This process seems to be the main issue among guidance, as some models are struggling to saturate through the dry air mass from the surface high pressure across the north and east, while others indicate the lift will be sufficient to produce enough hydrometeors to saturate through the dry low levels.

NBM and ensemble guidance has started to follow this drier trend in the guidance, resulting in snow amounts around an inch or less being forecast. However, not particularly buying this trend. While guidance is trending drier and cross sections struggle to saturate, the dry air around the low isn't overly robust, so if we get the progged lift of 10 to 20 microbars and can saturate through, the system will augment the environment below it and allow for a sustained area of better saturation. This solution is popular in the GFS suite of models, as well as the 18z HRRR and 15z RAP which receive their boundary conditions from the GFS. In these solutions, a swath of 2 to 4 inch amounts are being forecast through central Iowa with lower amounts on the northern fringes where lift is weaker and drier air is better able to impede the top down saturation. While the expansiveness of the higher amounts in these solutions may be overdone, the signal is there for pockets of higher amounts in that 2 to 4 inch range punching through the dry low-level air. Should this signal persist and lock in on a more favored area this evening, snowfall amounts may need to be increased and headlines considered.

After this accumulating snow moves through, the same solutions mentioned above indicate dry air cutting into the mid-levels and shutting off ice introduction aloft through late Wednesday night and into early Thursday morning. This leaves a few hours of 1 to 2 km deep saturation through the early morning hours roughly along Interstate 80 and south. With weak lift still present, as well as low-level wind shear in the saturated layer, this suggests the potential for more super-cooled liquid production and ultimately a freezing rain/drizzle developing overnight. With dry air and high pressure to the north, this saturation may only last a few hours, but could still leave some light icing on the ground for the Thursday morning commute. With guidance struggling to create this low-level saturation in the first place, like the snow, this isn't a persistent signal across all solutions, but it's certainly something to keep an eye on as it could have implications for travel on Thursday morning. With model solutions evolving as we speak, will be watching trends closely as the beginning of this system draws nearer. Dry conditions and slightly warmer temperatures are then expected through the day Thursday, helping to melt any ice or snow on roads.

LONG TERM /FRIDAY THROUGH TUESDAY/

Issued at 257 PM CST Tue Feb 24 2026

Another wave passing through the Great Lakes region will bring westerly flow aloft and southerly flow at the surface, resulting in warmer conditions on Friday. This will be a good setup for warm temperatures with the clear skies and compressional heating aloft, but extensive snowpack likely still in place will work to hold high temperatures down during the day. Current NBM highs in the mid to upper 50s over the current snowpack are likely too high, as the snow will actively cool the air as it melts. Expect this to dial back over snow covered areas in the coming days. That said, areas without snow will likely warm quite substantially and dewpoints near or above freezing should make a healthy dent in the snow pack.

At least low end precipitation chances then develop Saturday through the beginning of next week as a wave passes to the north of the area on Saturday and another, potentially more prominent system passes through toward the end of the weekend or early next week. However, the current precipitation forecast is likely overdone temporally as NBM tries to capture differences in timing with these systems in the models. With such spread in guidance, it's not worth speculating on a specific time, but main takeaway is at least an active pattern continuing through the end of the weekend and into next week.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 541 PM CST Tue Feb 24 2026

VFR to prevail for much of the period. Confidence increasing in a band of snow affecting FOD and DSM late in the period. Have added Prob30 groups to reflect, the duration of the snow will last beyond 00z.

DMX WATCHES/WARNINGS/ADVISORIES

None.