It's a common misconception that a single pattern is responsible for long term weather anomalies, such as a drought. In reality, it is usually a succession of several different patterns that all produce similar weather anomalies for a particular location that causes the long term weather anomalies. More simply put, your area has been dry since spring, but we have had several different patterns occur for several weeks at a time that have combined to produce these results.
There are times when a dominate pattern sets up and persists for many months and produces weather anomalies. Such was the case in 1988. In that year, a massive upper air ridging pattern set up shop across the central US and produce hot and dry weather from the Rockies to the Appalachians. Severe drought impacted areas from the northern Rockies to the Midwest.
I do not have the actual data in front of me for 1988, so I do not know how well this year matches up with 88 for your individual locale, but I was part of a NWS team that produced extensive review products of the drought of 88 and can say that what is going on across the central US this year pales in comparison to that in 88. Again, I am talking about the entire central US and not a particular location.
For what it is worth, here are the numbers for this year: Since April 1, Green Bay has seen 7.9" of rain, which is 76% of average. Wausau has seen 11.05" of rain, which is 96% of average.
-John
