A Warming Climate May Be Leading to an Increase in Heavy Rain Events

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The recent wet pattern across much of the Midwest, and country, has many wondering when, if at all, we’ll get a break from the very active pattern. 

Unfortunately it doesn’t look like the pattern will change anytime soon with more rain, and possibly severe weather, for the last week of May.  High pressure anchored over the southeast has placed the most active part of the jet stream across the southern and central Plains, right into the Midwest and Great Lakes.  Numerous days of severe weather over the Plains and heavy downpours in the Midwest are a result of this type of pattern as it pulls in quite a bit of Gulf moisture.  But it’s not just this short-term pattern that’s been causing the more heavy rain events. 

According to Climate Central the average annual precipitation from 1950 to 2018 has gone up in 90% of the states analyzed, with the eight largest increases having all come from the Northeast and Midwest.  Heavy rainfall is a sign of climate change.  For every one degree Fahrenheit increase in temperature, the atmosphere is able to hold four percent more water vapor leading to more frequent and heavy downpours.

Since 1950 the annual average precipitation has increased in Illinois between four to six inches, not only having an impact on the amount of rain that occurs, but also increasing the overall streamflow within some of the local rivers.  According to the USGS the average annual streamflow into the Rock River at Rockton – which is measured often by the USGS – has increased 80% since the 1950s!  This means the river is running higher than it has in a very long time.  And a higher than normal river level will lead to more frequent river flooding with higher than normal rainfall events.

Unfortunately this could become more of the norm as our climate continues to warm.  So far precipitation to date in Rockford has added up to 18.94 inches, making it the 5th wettest year to date on record.  Within the top 10 wettest years to date on record, three of those years fall within this decade! 

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