Tuesday, May 12, 2020

Heavy Rainfall Threatens Parts of the Stateline

Skies are expected to remain mostly dry through much of Wednesday afternoon, but the chance for rain and thunderstorms will increase Wednesday evening and overnight with the arrival of a warm front. A pattern shift mid to late week will bring an increased risk for repeated rounds of thunderstorms from the Plains to the Great Lakes, possibly impacting northern Illinois and southern Wisconsin. The first threat for heavy rainfall arrives Wednesday night as a warm front lifts north through Illinois. The
arrival of the front will also bring in copious amounts of moisture, leading to the risk for heavy rain producing storms through Thursday morning. As of Tuesday evening, it looks like some areas could receive half an inch, possibly up to an inch, of rain by Thursday morning. The risk for severe weather is low, but some elevated storms could produce small hail during the overnight. It's likely the storms will continue into mid-morning Thursday with a break, or at least a little more dry time, Thursday afternoon.

By Thursday evening, a cold front will move in from the north and northwest bringing another chance for thunderstorms across portions of northern Illinois, moving into central Illinois, by the evening. Depending on sunshine during the afternoon Thursday, the risk for strong to severe storms will be possible, but right now that risk looks a little more focused to the south. 

High pressure will then briefly move in for Friday likely keeping the heaviest rainfall focused to the south along a stationary boundary. That boundary will then be pulled back north Saturday and Saturday night, bringing back the chance for heavy rain and thunderstorms into Saturday morning.

Moisture in the atmosphere will remain exceptionally high through the end of the week and weekend. This means that as thunderstorms develop and move through heavy rain, and repeated rounds of rain, will be possible along the stationary boundary. Rainfall totals in excess of three inches will be possible in some of the hardest hits areas. This could cause some problems for local rivers, as rivers could rise through the weekend. Those in flood-prone areas, as well as long the rivers, should pay attention to the forecast this week. 

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