Close to the Edge Over the Weekend

Temperatures Thursday warmed into the upper 60's and low 70's.  Rockford reached 70 degrees for the first time in the month of May.  The warming trend will continue into the weekend, with most of the weekend staying dry.  However, I'm holding on to a very small precipitation chance Friday and Saturday because of the placement of the jet stream overhead. 

A ridge of high pressure will begin to move east for the start of the weekend.  Underneath that ridge, temperatures are expected to continue their climb, possibly reaching the middle to upper 70's on Mother's Day.  Friday and Saturday, northern Illinois and southern Wisconsin will be on the outer edge of the jet stream providing the warmth.  Think of the jet stream as an 'interstate' for storm systems to travel along.  If we're close that interstate, we run the chance for storm systems - weak or strong - to move through.  This will be the case the next couple of days.  Several weaker low pressure systems will move along the flow in the jet stream.  As the low approaches, air from the surface will begin to rise.  Rising air, if conditions are just right, induces precipitation.  But if we look at the whole atmosphere going into the weekend we'll find a decent amount of dry air down near the surface.  If precipitation were to occur, there would be a good chance that it would evaporate before ever reaching the ground.