It is safe to say that last September compared to this September in North Central Wisconsin has been a tale of two completely different months. Last year, Wausau experienced the driest September on record with only 0.23" of rain, while temperatures for the month reflected that more of late summer than fall, running 3 degrees above average. Fast forward to this year, and we have had the 5th wettest September on record, while temperatures have averaged about 3 degrees below average. Polar opposites indeed.
Of course what will be most memorable when we look back on this September was the flooding rain that impacted much of central and western Wisconsin on Sept 22nd & 23rd. We knew about 5 days ahead of time that there was a good risk for moderate to heavy rainfall in the Badger State on Thursday the 23rd. The various computer guidance models were forcasting the heaviest rains to actually fall across the northern tier of the state early on in the week, before adjusting the risk area a bit farther south in central Wisconsin a couple days before the deluge of rain hit. Rainfall totals ranged from 2-6" in much of our viewing area, with the highest amounts being found in parts of Wood & Portage County in the 5-7" category. Here is a radar estimate of total rainfall from the storm from the National Weather Service in La Crosse.
More details on rainfall totals in parts of viewing area and portions of western Wisconsin can be found on this link from the NWS in La Crosse. The heaviest rain fell in SE Minnesota were over 10" was measured.
As you'll recall, flood watches were initially posted leading up the the storm from roughly Marathon County on northward, later having most of the other counties in our viewing area (with the exception of Juneau, Adams & Waushara Counties) added on as the rain began to fall. Although there wasn't any one particularly heavy line of storms that rolled across the region, there was a sustained flow of moisture traveling northward into the Wisconsin River Valley. The rain came down at its hardest during the nighttime hours Wednesday and continued moderate to heavy at times on Thursday. Rainfall amounts of .50-1" per hour where common during those stretches of time. Of course as the ground became more saturated, it was only a matter of time before the runoff would lead to flooding as drainage ditches and culverts became filled, while area streams and rivers began to approach flood levels. The worst of the flooding took place in Marathon City, Babcock and in Wisconsin Rapids where flooding was a direct effect of the rising rivers in those areas. There were many other locales that also had some flooding in low lying spots for a time, but not quite to the extreme that took place in Marathon, Wood and Portage Counties. As time went along, the flood waters had to flow downstream and that was the case southbound along the Wisconsin River in Wisconsin Dells and Portage, where the river crested above flood state on Monday. Historically speaking, this is at least the 4th major flood to impact the state since 2005. Previously we had flooding in Antigo in late March 2005, the heavy rains that lead to the breaching of the dam on Lake Delton in 2008 and earlier this summer the severe storms that dumped 8-15" of rain in SE Wisconsin near Milwaukee. Probably most interesting about this particular wet weather event was that it took place in early fall. A lot of times we'll experience flooding during the spring due to a combination of melting snow, heavy rain and ice jams, while the summer typically is the season with convective storms that can dump lots of rain in a short period of time. However, as this case illustrates, there is no one time of the year that flooding can't take place.
On a side note, it almost is mind boggling that a century old levee in Portage, known as the Caledonia-Lewiston levee is still their means of protection from the risk of flooding. If there is one thing we have learned over the past several years, levees and dams should be checked on a regular basis and if the structure is that old, something needs to be built to a higher standard to replace it. Unfortunately, it is only after flooding events like this that officials may consider the need to fix this. No less, one would have thought after what went down in Lake Delton a couple years back, that would have been a wake up call to many municipalities to see how strong their dams, levees, etc are structurally? Will the aftermath of flooding due to this storm, which lead to a state of emergency in various counties in the state be that wake up call? Honestly, I'm not sure, but I certainly hope it gets the inspections process in motion.
Meantime, as we are about to leap into October, the tail end of the growing season has arrived. Nighttime lows since the start of this month have flirted with or dropped below freezing in the Northwoods, while the mercury has dipped into the 30s on at least a handful of nights in Central Wisconsin. So when is the average first frost date for your area? Below is a map and here is a breakdown by cities in the area from the National Weather Service in Milwaukee and Green Bay.
Enjoy those warm and sunny days when you can, because as we all know much chillier weather is bound to invade as we push toward the end of the year.
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