Sunday Evening Weather Update

12:30am Update: Scattered showers and thunderstorms have developed mostly over Wisconsin and northeast Iowa late Sunday night.  Activity will most likely remain to the north and northwest over the next hour (through 1:30am-2am) and then begin to move into northern Illinois between 3am and 4am.  Still looks like hail would be the biggest concern as some of the stronger storm cells are suggesting hail getting close to one inch in diameter (up north over Wisconsin).  Expect thunderstorms through sunrise Monday, coming to an end after 8am/9am. 








9pm Update: The Storm Prediction Center has place most of northern Illinois under a 'Slight Risk' for strong/severe thunderstorms during the overnight.  The overall threat for severe weather remains low, but there are some indications that some of the stronger thunderstorms could produce hail.  It looks like our skies will remain dry through at least Midnight with storms developing between 1am and 3am.

Skies Sunday were filled with cloud cover and an occasional light shower or sprinkle during the early evening.  A cluster of showers and thunderstorms developed in Iowa Sunday afternoon and moved east of the Mississippi River.  The southern edge of the showers intensified rather quickly once moving into Illinois due to higher instability south of a stationary boundary.  While the weather is rather quiet it looks like thunderstorms will redevelop during the overnight and early Monday morning.

A stalled out warm front/stationary boundary has been in central Illinois nearly all weekend.  This is why temperatures were in the 50's Friday and Saturday, and in the 60's Sunday afternoon.  While the environment will be rather stable in northern Illinois at the surface of the earth, up above the atmosphere will become slightly unstable late tonight and overnight.  This could lead to scattered showers and thunderstorms develop after Midnight and lasting through early Monday morning.  Biggest threats with storms tonight would be heavy rainfall and possibly large hail as storms would be mostly elevated (meaning

they would form over-top the stable air near the surface).


It looks like the storms would last through roughly 8am/9am Monday before shifting east and southeast.  A break from some of the rain will likely occur through most of Monday before thunderstorms redevelop late afternoon and evening.  This threat, however, may be a little focused southward of northern Illinois.  All depends on where the stationary boundary ends up.