Sunday, April 28, 2019

Active Pattern Leads to Mulitple Rounds of Heavy Rainfall this Week

Record breaking snow came down over northern Illinois Saturday afternoon and evening but the focus will shift from the snow, to heavy rainfall in the upcoming week.

Several rounds of heavy rain will be likely going into the first week of May, with the first round arriving late Sunday night.  High pressure Sunday afternoon will continue to shift east of the Great Lakes Sunday evening.  Clouds will increase ahead of the rain, and isolated thunderstorms, beginning to develop over southwest Iowa and northern Missouri.  Skies will remain mostly dry through about Midnight over northern Illinois and southern Wisconsin.  Rain showers are expected to increase from the southwest after Midnight, becoming heavy at times by Monday morning.

Rainfall totals could reach three quarters of an inch, up to an inch of rain by Monday afternoon.  The first round of rain will be progressive and shouldn't cause too great of a concern for flooding.  However, ponding water on the roads and even some standing water in ditches and fields will be possible.  Skies will stay dry Monday afternoon and evening before the second round of rain moves in Tuesday.  This second round will develop ahead of a warm front that will slowly be lifting through central Illinois.  Instability won't be too high, but an isolated thunderstorm or two remain possible through Tuesday evening.

Increasing moisture with the arrival of low pressure Tuesday night will bring a greater threat for heavy rainfall to parts of northern and central Illinois.  Rainfall totals could reach over one inch by Wednesday morning.  Between Sunday night and Wednesday night rainfall totals could range between 2-3 inches across northern Illinois.  With a couple inches of rainfall possible, concerns are elevated for the potential for flooding later this week.  Something we'll need to keep an eye on in the days to come.

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