Tuesday, April 16, 2013

All you need to know regarding the weather this week

The stage is currently being set for what could end up being a significant flooding event for the Midwest, including southern Wisconsin and northern Illinois.  Flood Watches have been issued for Green, Rock and Walworth counties and I wouldn't be surprised to see additional watches issued for northern Illinois within the next day.  This will also coincide with the Flood Warnings that are already in place for the Rock and Pecatonica Rivers.  Many rivers have reached minor flood stage with areas north of Rockford and west towards Freeport reporting flooding.  The expected rainfall Wednesday and Thursday could push rivers to moderate, possibly even major, flood stage by Friday night.

Image: Milwaukee/Sullivan NWS
Forecast River Flood Levels

This image is from the Milwaukee/Sullivan NWS office representing the forecast for river levels in southern Wisconsin and northern Illinois.  Note the purple dots indicate major flooding which is expected to take place on both the Rock and Pecatonica - not to mention smaller rivers, creeks and streams.

A very strong spring storm moving into the southwest this afternoon will lift towards the Central Plains late tonight and early Wednesday.  A complex of thunderstorms are expected to develop near Kansas and Oklahoma and lift northeast into Iowa, Missouri and possibly Illinois by early Wednesday.  A developing warm front in central Illinois will lift north near I-80 Wednesday afternoon pulling warm, moist air in from the Gulf of Mexico.  This warm, moist air will overrun the cooler air across northern Illinois Wednesday afternoon at the same time a weak upper level disturbance will be moving through.  Severe weather will be likely Wednesday from north Texas, Oklahoma, Kansas, Nebraska, Missouri, Iowa and west-central Illinois and coming very close to I-88 late Wednesday afternoon.  Of greater threat for the Stateline remains the heavy rain potential.  Low pressure at the surface will then move closer to the Great Lakes with moderate to heavy rain, and possibly a line of strong storms, expected to move in overnight Wednesday into Thursday morning.  This round could bring 1"-2" of rain for northern Illinois and southern Wisconsin.  Those storms will move east with another round expected to develop as the main system moves through Iowa, Wisconsin and Illinois late Thursday.  Depending on how far north the low tracks Thursday could mean a few stronger storms would be possible for us late in the day.  Forecast models have been very consistent in developing a heavy rain scenario with nearly 3" to even 4" of rain falling from Wednesday afternoon through Friday morning.  If we were to see that much rain many rivers would be pushed to major flood stage and flash flooding would become an issue. 

The low will then move into Michigan by Friday morning with colder air wrapping in from the northwest.  A mix or transition over to snow may occur Friday morning.  Accumulating snow won't be that far away from Wisconsin to Minnesota.  Daily updates will continue straight through the week.  We've also uploaded all the latest flooding information on the right hand side of the blog. 

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