Moderate Drought in Central Wisconsin
By Justin Poublon
August 21, 2018 - 9:30 AM CST | 9 0
Welcome to 2018 Wisconsin where we have record flooding and moderate drought occurring simultaneously.
The drought monitor has central Wisconsin in Abnormally Dry to Moderate Drought (D1) category. According to the AHPS precipitation Analysis tool , 60 and 90 day precipitation departure from average is -6.0" for many counties in central Wisconsin. Clark, Wood, Monroe, Jackson and Eau Claire counties are driest relative to average. Meanwhile just a few miles away in southern Wisconsin a surplus of 8.0"+ has been observed.
It's common for summer precipitation to be poorly distributed spatially, even on a county level. A localized thunderstorm could impact the downtown while suburbs stay completely dry. The upper Mississippi Valley depends on large mesoscale convective system's (MCS) to provide widespread rain in summer. These systems occur as a result of thunderstorm activity. When thunderstorm events are weaker, the MCS activity is below average. In 2018 we've seen pretty much no MCS activity across central Wisconsin hence the drought that has developed.
Interesting note - Southern Wisconsin flooding rain events recently were driven by abnormally strong low pressure systems passing slowly over the region, not mesoscale convective systems.
To make matters worse, dry-hardened soil will act like concrete driving rain to runoff before allowing it to soak in. It takes time to penetrate the hardened soil. With a single thunderstorm the rain comes and goes quickly. Central Wisconsin doesn't need 15 inches of rain overnight. Yes it would improve the dry conditions but create other issues (just as the folks in Cross Plains!) Wisconsin needs a long duration, widespread, preferably light-moderate intensity soaking rain event.
Late August Rain Outlook
The Climate Prediction Center 6-10 day outlook shows high rain probabilities in late August for drought areas of northern & central Wisconsin. With the increased rain probabilities will come above average temperatures. Long range forecasts can be tough this time of year due to lower predictability but I would say confidence is good right now. 8-14 day probabilities are encouraging as well.
We are seeing these outlooks play out on the GFS model .There could be multiple days with thunderstorms and heavy rain in Wisconsin beginning Friday Aug 24 into early next week. We will be covering it closely. It certainly looks like rain will favor central and northern Wisconsin this time. Stay tuned!
Here is the 7-day forecast to close showing decent rain chances on Friday and Sunday, Monday for the Wisconsin Rapids location.