textproduct: Des Moines

KEY MESSAGES

- A quick shot of light snow in some areas this morning, but with little impact. More light snow this afternoon and evening, mainly in northern and eastern Iowa, along with strong northwest winds across the state. This combination of snow and wind has prompted expansion of the Winter Weather Advisory, which is now in effect for most areas along/north of Highway 30.

- Very cold tonight into Monday morning, as winds are slow to diminish and temperatures fall to near or below zero. This will lead to dangerous wind chill values, and the Cold Weather Advisory has been expanded into much of central and southeastern Iowa.

- Not as cold from Tuesday through Thursday, with some low snow chances north at times.

DISCUSSION

Issued at 243 AM CST Sun Jan 18 2026

A surface high pressure ridge sliding by to our southwest allowed for light winds and mostly clear skies several hours ago, with temperatures falling to near or just below zero. Winds have begun to come around to southwest overnight and clouds have gradually increased, helping temperatures to stabilize but still resulting in another cold night across the region. Meanwhile, a trio of mid-level shortwave impulses is approaching quickly from the north northwest. The first impulse will move over our forecast area early this morning, coincident with low-level warm air advection in the aforementioned southwesterly flow. Forecast soundings show a brief period of saturation and weak forcing for ascent associated with this conjunction, and forecast models continue to produce light snow in a roughly north-south band that will sink southeastward into our area in a few hours, but then likely fade out by the time it reaches our eastern counties as it encounters a relatively drier environment. Regional radar already evinces the development of this snow band, though it is not yet reaching the surface for the most part, with only a couple of surface observations of snow in South Dakota as of 2 AM. At any rate, this early morning snow will be light, transient, and of little impact, but may cause brief minor travel issues due to slick spots on area roads, mainly in our western and northern counties.

There will be a brief lull in wake of this leading band of light snow, but then the second mid-level shortwave will barrel through this afternoon, pushing with it a strong surface trough that will sweep from northwest to southeast across our service area during the afternoon. Strong cold air advection and a tight pressure gradient will support strong and gusty northwest winds behind the front, persisting through the evening and into early tonight. It appears the tightest pressure gradient, strongest cold air advection, and strongest 925 MB winds overlap best in northern and northeastern Iowa. Wind potential is thus maximized in that area, where the probability of reaching Wind Advisory criteria is approximately 60%. In addition, forecast soundings this afternoon show that the cooling above the surface and cold air advection will enhance mixing and may result in weak surface-based instability and a possibility of light snow showers. However, moisture will be very limited and forecast CAPE values are low in our area, generally 10-20 J/KG, minimizing the threat of any stronger snow squalls. Nevertheless, light snow is likely especially in our northeast, closer to the passing mid-level impulse, and have continued to advertise high (60-70%) POPs in that area this afternoon. Despite forecast snow amounts of only about an inch or less, the combination of the snow with the gusty winds could result in visibility reductions and hazardous travel conditions. In light of this, have expanded the pre-existing Winter Weather Advisory over to our northeastern areas around Tama, Waterloo, and Waverly.

Any lingering light snow/snow showers will end by later this evening, however the winds will be slow to diminish overnight. As temperatures plummet below zero across northern Iowa and to just a few degrees above zero in the south, this will result in dangerously cold wind chill values across much of the state overnight into Monday morning. Have expanded the Cold Weather Advisory through our central and southeastern counties, and it is now in effect for most of our forecast area excepting only our southwestern counties. The third 500 MB wave will move over northeastern Iowa and neighboring states around Monday evening, but soundings look dry and additional snow is not anticipated. Another series of impulses will move through the broadly cyclonic flow aloft between Tuesday night and Wednesday night, but Iowa will reside beneath the southern fringe of their influence and only low (20-30%) POPs are carried in northern Iowa at times, notably around Tuesday night with the first impulse in this new series. Temperatures will gradually moderate in this scenario, with afternoon highs Wednesday and Thursday ranging from around 20 northeast to mid-30s southwest.

A pattern change will finally take place late in the coming week. By around Friday the 500 MB cyclonic flow pattern will shift eastward, placing Iowa beneath brisk roughly zonal flow aloft, while a broad trough swings down into the western U.S. As that trough approaches the central U.S. next weekend, it will likely lead to renewed precipitation chances in our region, but any further details are murky at this range.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 532 AM CST Sun Jan 18 2026

VFR conditions will prevail for the next several hours, but then deteriorate this afternoon and evening as a cold front surges across the area. Behind the front winds will turn to northwest and become strong and gusty, resulting in 20+ crosswinds on some runways. Low stratus clouds will also spread in producing MVFR visibilities around FL015-025, and scattered snow showers will produce sporadic reduced visibility to 3SM or less in falling and blowing snow. Probability of such impacts is highest at MCW and ALO, and lowest at DSM and OTM. Any snow will move out this evening with VFR conditions returning overnight, but winds being slow to diminish.

DMX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 9 PM CST this evening for IAZ004>007-015>017-023>025-033>035.

Winter Weather Advisory from noon today to 9 PM CST this evening for IAZ026>028-036>039-048>050.

Cold Weather Advisory from 9 PM this evening to noon CST Monday for IAZ004>007-015>017-023>028-033>039-045>050-061-062.

Cold Weather Advisory from 1 AM to noon CST Monday for IAZ058>060-072>075-083>086-095>097.