Full-blown winter appears here to stay with another round of snow impacting Iowa on Monday into Tuesday. Totals from this event were much lighter with just an inch or two most commonly reported over southern and southeastern Iowa. As a reminder, the IEM generates these maps for snowfall events that have at least an arbitrarily chosen two inch or greater report and/or significant travel impacts. You can find previous event maps for this year and previous years by following the "winter2526" tag associated with this feature message. The next snowfall event arrives this evening, but totals are again expected to be on the light. A bit of quieter weather arrives for the remainder of the week.
The snowfall from this past weekend was quite intense for November. The featured chart presents top 10 daily snowfall totals for Des Moines during the month of November. There are caveats galore with such a listing including difficulties of snowfall measurement, varying periods of record, and most importantly: snowfall events are typically long duration and often cross arbitrary 24 hour boundaries more so than heavy rainfall events. All those caveats aside, the total from Saturday at 8.9" comes in third place for the month of November. This was also the case for Waterloo, with its 9.3" coming in third place as well.
After a mild start on Wednesday morning, an arctic front swept the state and ushered in much colder temperatures and the coldest air of the season to date. Low temperatures this Thursday morning are well below zero and likely record lows for today for many sites in the state. The featured chart looks into the accumulated frequency of having the season's first low temperature of the given threshold by the given date of the season for Ames. The chart plots as a percentile over all years, so there are some years that failed to reach the given threshold and that is why the accumulated value does not reach 100 in all cases. The side table shows the percentile dates for each threshold. Having such cold weather by 4 December comes in around the 10-25th percentile of so, so about once or twice per decade to experience such cold temperatures this early for the given thresholds plotted.
The featured chart presents monthly average temperature departures for Ames with the monthly Niño 3.4 index values since the start of 2018. The value of this index drives the designation of either La Niña (negative value) or El Niño (positive value) state with values between -1 and 1 considered as "weak". So we have spent much of 2025 in a weak La Niña state with the present forecast not calling any additional strengthening, so remaining weak. Much is made of using this index to make monthly/seasonal scale forecasts for weather over the globe due to the importance of the equatorial Pacific Ocean basin for global atmospheric circulations. As the chart shows, it is certainly not a simple relationship between this index and monthly temperature departures for a location in the center of Iowa!
