textproduct: Des Moines

KEY MESSAGES

- A band of accumulating snowfall (100% chance) will occur across parts of northern and northeastern Iowa from this afternoon into tonight, with lower snow chances (30-50%) and amounts farther south. While the precise location of the accumulating band and amounts within it are somewhat uncertain, confidence in several inches is high enough for a Winter Weather Advisory from around Algona over to Mason City and Waterloo. The evening commute will likely be affected in these areas.

- A second front will move across Iowa on Wednesday afternoon, bringing strong and gusty winds, scattered snow showers, and blowing snow in areas that receive around an inch or more today into tonight. Hazardous travel conditions may develop due to the combination of strong winds, snow showers, and blowing snow.

- Very cold weather is forecast from late Thursday through Saturday. Low temperatures both Friday morning and Saturday morning will be below zero statewide, and approach -20 degrees in some northern and northeastern areas. Dangerous wind chills may result.

DISCUSSION

Issued at 328 AM CST Tue Jan 20 2026

It has been a cold but quiet night across the area with a surface high pressure ridge sliding through the region. A patch of clouds has stubbornly clung to our southern counties, keeping temperatures there about 15-20 degrees warmer than areas to the north where skies are clear, as light to calm winds have allowed for good radiational cooling conditions. The clouds are moving slowly east southeastward however, so it is likely most or all of the remainder of our area will get in on the cooling party before the sun comes up. Fortunately with no wind, impacts from the cold are mitigated below hazardous thresholds.

As has been advertised for the last few days, a clipper system is set to bring snow to portions of our service area later today into tonight. A broad surface low pressure trough has already developed along the lee of the Rockies in advance of an approaching 500 mb shortwave, and as the mid-level system moves southeastward toward Iowa today it will cause the surface trough to shunt southward, then reorient and eventually close off as a surface low moving through Iowa tonight. Initially, as the surface ridge currently in places moves off to the east today and the trough slides down the High Plains to our west, a band of warm advection between the two systems will set up roughly along the Iowa/Minnesota border, arcing east southeastward into northern and northeastern Iowa. As the trough approaches and then moves through the area tonight, forecast soundings and vertical cross-sections continue to depict bands of frontogenetical forcing resulting in lift within the DGZ and a deep saturated profile. This supports a band of accumulating snowfall developing within the aforementioned warm advection region, tracking roughly parallel to its orientation as the system moves through, and likely over our northern and northeastern counties. Meanwhile, as the surface low deepens and moves eastward across Iowa tonight, it will pull a trailing surface trough through which should also provide a focus mechanism for a more southwest-to-northeast oriented snow band. Have greatly expanded POPs almost down to the Missouri border accordingly, however, this feature will be more transient and thus result in lower snowfall amounts and lesser impacts. There is high confidence in several inches of snowfall within the warm advection band over northern and northeastern Iowa, however, short-range model solutions have trended southward by about 40 to 60 miles since yesterday, and while they appear to have stabilized tonight, there is some uncertainty as to where the relatively narrow band of highest accumulations will fall. Nevertheless, with the potential for 2-3 inches or locally higher, beginning around the evening commute window, have elected to issue a narrow Winter Weather Advisory from mid- afternoon into tonight, for nine counties from Algona over to Mason City and Waterloo. If forecast trends for snowfall increase further, or for location of snowfall shift farther south or back north, then expansion of this advisory may be needed later today. While impacts will be mitigated by light winds, slick roads and difficult travel are still likely.

Unfortunately we will not get a break after the storm system later today-tonight, because on Wednesday a stronger 500 mb trough will follow hot on the heels of the first one. As this second trough moves over Minnesota and northern Iowa during the day on Wednesday, it will pull a sharp surface trough along with it, surging through our forecast area during the afternoon. Very strong winds aloft will follow the trough, with forecast soundings showing a deep mixed layer up to about 8000 FT and winds of 50-60 KT at the top of the mixed layer. With relatively steep lapse rates above the surface and all models resolving a brief but intense band of cold air advection behind the trough, efficient mixing should allow for good downward momentum transport and at least a few hours of strong and gusty winds behind the trough. Have therefore increased the forecast wind speeds and gusts significantly on Wednesday afternoon, but not yet to advisory criteria - this potential will be closely monitored in subsequent forecast updates and an advisory may be possible by the time we get to Wednesday. Also of note is the strong frontogenetical circulation depicted along the surging trough, and area of surface-based instability behind it due to rapid cold air advection aloft. This supports a potential for snow showers or even snow squalls, once again, with SBCAPE of 50-75 J/KG indicated by the NAM and other high-res models. A relative lack of moisture will be a mitigating factor, but the potential justifies significant expansion of POPs Wednesday afternoon with a 20-40% chance now advertised across much of our area. Even aside from any snow showers/squalls that may occur, the strong northwest winds sweeping across areas that receive accumulating snowfall later today will result in areas of blowing snow. Given the combination of strong winds, blowing snow, and snow shower potential, hazardous weather will once again be possible around Wednesday afternoon and perhaps lingering into the evening.

Once the second storm system moves off Wednesday night we will thankfully, mercifully, see a period of drier weather with no significant precipitation chances for at least a few days. However...that does not mean the weather will be uneventful, unfortunately. A large gyre over Canada will draft southward in the second half of this week, reaching far southern Ontario by Thursday and pushing a large, Arctic surface high pressure area from southern Canada down into the Midwest. The arrival of this airmass will be heralded by a cold front moving through Iowa during the day Thursday, with temperatures plummeting thereafter into the weekend. On Friday *high* temperatures will range only from the single digits above zero southwest to near 10 below in the northeast, while on both Friday morning and Saturday morning temperatures will fall below zero across the entire state, and may approach 20 below zero in the north and northeast on either or both mornings. While winds during this time will not be strong, even a modest breeze at such cold temperatures could result in dangerous wind chills, and we will likely see long- fuse cold weather headlines at the end of the week.

Finally, as if all that wasn't enough, by the latter half of next weekend a longwave 500 MB trough will set up roughly from the Midwestern states southwest to around the Four Corners region, with one or more impulses ejecting out of the southwestern portion of the trough over the southern High Plains and central U.S. Long-range forecast models are resolving a large precipitation shield developing in response to this scenario, and while it largely remains south of Iowa, its proximity is such that any more northward track or orientation of the system would bring a return of snow chances to our area, perhaps around Saturday night to Sunday night. Obviously, confidence in such details is low at this range, but it certainly doesn't look like our overall active weather pattern is going to quiet down within the next week.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1159 AM CST Tue Jan 20 2026

Snow will develop across western Iowa this afternoon, then move eastward through the area tonight. Widespread MVFR to IFR conditions will occur over FOD/MCW/ALO after 23Z, where the heaviest and most persistent snowfall will occur. Conditions will gradually improve after 06-08Z. Farther south lighter snowfall is anticipated, and hence CIGs and VSBYs impacts are less likely and will be of shorter duration, although a period of lower CIGs may persist behind any falling snow. Winds will favor a southerly component through early tonight, shifting w/nwly.

DMX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory from 3 PM this afternoon to 3 AM CST Wednesday for IAZ005-016-017-025>028-038-039.