Low pressure underwent lee cyclogenesis as it moved out of Colorado, across the central plains and into the Midwest. Initial broad isentropic lift allowed for precipitation to develop, with light rain in southern Iowa and snow in northern Iowa.
Every event with a place to put it; 9 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS DMX wrote it up.
Low pressure underwent lee cyclogenesis as it moved out of Colorado, across the central plains and into the Midwest. Initial broad isentropic lift allowed for precipitation to develop, with light rain in southern Iowa and snow in northern Iowa. Across northern Iowa, snow rates increased later in the day as frontogenesis reached the area. This resulted in a narrow band of heavy snow in far NW Iowa into Minnesota. As the low deepened the pressure gradient tightened across the state, resulting in gusty 25 to 35 mph winds and periods of significantly reduced visibility in blowing snow.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Des Moines, IA wrote its last area forecast discussion before the first event at Dec 10, 5:53 AM CST, 2 hours 7 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 553 AM CST Fri Dec 10 2021 ...Updated for the 12z Aviation Discussion... .DISCUSSION.../Today through Thursday/ Issued at 309 AM CST Fri Dec 10 2021 Key Messages: - First significant winter storm of the season for Iowa today with heavy snow across northern Iowa and light ice possible central and east, accompanied by gusty winds - Much warmer into next week, in record territory The much advertised Winter Storm is knocking at our doorstep as snow began falling across Nebraska overnight. The surface low will continue to deepen as it lifts out of the central plains and into the upper midwest through today. Central and southern Iowa will sit within the warm sector of the system for the first part of the day and temperatures were nudged up a couple degrees here to account for some of the warming trends seen in recent hires model runs. This could also set up a potential fog scenario with good moisture in place, however confidence in this is not high and at this time most models don't indicate indicate reductions to visibility. Something to monitor for changes later. Light snow is expected to begin across northwest Iowa around midday, intensifying late afternoon and this evening as mid level frontogenesis supports banding and heaviest snow rates. RAP/GFS soundings in northern Iowa indicate pretty deep dendritic growth layers after 00z with good lift through the layer, supporting high snow rates and higher than average snow-to-liquid ratios (climatology for Iowa is ~13:1 and ratios were increased to ~15:1). Snow rates are forecast to diminish overnight as stronger forcing shifts east. Deformation zone snow will linger across northern Iowa through the early morning hours before exiting around sunrise. Accumulations of 8+ inches are expect northwest with 5+ inches across the remaining portions of northern Iowa. The gradient is fairly tight from northern to central Iowa thanks to the banding that will enhance totals across northern Iowa and a transition to mixed precipitation into central Iowa. Soundings across central to east central Iowa support initial drizzle/freezing drizzle ahead of the front before fully saturating to allow for ice introduction and a transition to snow. Light ice accumulation is possible, a few hundredths in the vicinity of Story/Marshall/Tama/Black Hawk counties and surrounding locations, so the Winter Weather Advisory has been expanded to account for this. Winds will also be a concern Friday night into Saturday morning as the pressure gradient tightens with strong cold air advection and subsidence on the back of the low. Soundings indicate 30+ knot gusts in the boundary layer, and while these won't be totally realized at the surface, it will be quite windy. Across northern Iowa where this is combined with heavy snow, drifting and visibility reductions due to blowing snow are a concern. Winds shift to southerly and warm air advection increases across the area beginning Sunday as upper level ridging slide towards the area. This regime will dominate the forecast for much of the upcoming week as breezy south winds pump warm air into the area. Snow pack across northern Iowa will initially keep temperatures cooler there early in the week while central and southern Iowa warm well above climatological normals. Wednesday looks to be the warmest (and windiest) day of the week with highs ranging from the mid 50s north to upper 60s central and south. A few spots could even touch 70 degrees, well into daily record territory and perhaps near all-time December high temperature records. Synoptic models continue to indicate a robust system middle to late week that could bring convection back to the forecast and will most certainly drop temperatures. Details are still quite fuzzy at this time range with significant model differences, but will be something to monitor in the coming days. && .AVIATION.../For the 12Z TAFS through 12Z Saturday morning/ Issued at 553 AM CST Fri Dec 10 2021 VFR conditions this morning will deteriorate by midday across northern Iowa as a strong winter system impacts the area, dropping to IFR or LIFR in northern Iowa by evening across all sites. Winds will transition from easterly to northwesterly today and overnight, gusting 20-30 kts at times. Heaviest snow and blowing snow will impact KFOD/KMCW beginning midday while KALO and perhaps KDSM may see a period of rain and/or freezing rain this afternoon before transitioning to light snow tonight. && .DMX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from midnight tonight to 6 AM CST Saturday for IAZ039-049-050. Winter Storm Warning from 9 AM this morning to 6 AM CST Saturday for IAZ004>007-015>017-023. Winter Weather Advisory from noon today to 6 AM CST Saturday for IAZ024>028-033>038-044>048. && DISCUSSION...Hagenhoff AVIATION...Hagenhoff
Hazardous Weather Outlook National Weather Service Des Moines IA 333 AM CST Fri Dec 10 2021 IAZ004>007-015>017-023-111200- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas- 333 AM CST Fri Dec 10 2021 This Hazardous Weather Outlook is for portions of northern Iowa. .DAY ONE...Today and tonight A Winter Storm Warning for moderate to heavy snow and blowing snow is in effect for the area later today through tonight. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .DAYS TWO THROUGH SEVEN...Saturday through Thursday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotters will not be needed for severe weather, but snowfall reports would be greatly appreciated. IAZ024>028-033>039-044>050-111200- Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-Webster- Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene-Boone- Story-Marshall-Tama- 333 AM CST Fri Dec 10 2021 This Hazardous Weather Outlook is for portions of northern and central Iowa. .DAY ONE...Today and tonight A Winter Weather Advisory is in effect for light to moderate snow, blowing snow, and a light wintry mix later today through tonight. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .DAYS TWO THROUGH SEVEN...Saturday through Thursday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotters will not be needed for severe weather, but snowfall or icing reports would be greatly appreciated. IAZ057>062-070>075-081>086-092>097-111200- Audubon-Guthrie-Dallas-Polk-Jasper-Poweshiek-Cass-Adair-Madison- Warren-Marion-Mahaska-Adams-Union-Clarke-Lucas-Monroe-Wapello- Taylor-Ringgold-Decatur-Wayne-Appanoose-Davis- 333 AM CST Fri Dec 10 2021 This Hazardous Weather Outlook is for portions of central and southern Iowa. .DAY ONE...Today and tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Saturday through Thursday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotters will not be needed. Small
The national radar mosaic for the moment the first event began.
9 winter storm. Local standard time, as filed.
A trained spotter reported 8 inches of snow in Estherville.
A total of 5.5 inches of snow fell with winds over 25 mph.
A total of 5 inches of snow fell with winds over 25 mph.
A total of 6.5 inches of snow fell with winds over 25 mph.
A total of 6.7 inches of snow fell with winds over 25 mph.
A total of 4 inches of snow fell with winds over 25 mph.
A total of 4 inches of snow fell with winds over 25 mph.
A total of 4 inches of snow fell with winds over 25 mph.
A total of 4 inches of snow fell with winds over 25 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2021Every state in 2021This day in weather historyWarnings in Iowa, December 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 994719, 994720, 994721, 994727, 994722, 994723, 994724, 994725, 994726.