Weekend Rainfall - Not a Complete Washout

It's been a week since any measurable rain has fallen in northern Illinois and southern Wisconsin.  Following a very rainy June, it's hard to believe that we are actually in need of rain, but we do need about an inch of rain per week during the growing season - June, July and August.

Skies will stay dry Thursday night as thunderstorm activity remains to the north over Minnesota and Wisconsin, closer tied to a cold front.  The front will slowly sink southward during the afternoon Friday, moving overhead by Saturday.  Ongoing thunderstorms to the north early Friday may push a little more cloud cover into northern Illinois during the day, but temperatures are expected to warm into the upper 80's, to low 90's by the afternoon.  Southerly winds will push the heat index in some locations up near 100 degrees.

While most of Friday will be dry, an isolated thunderstorm or two can't be ruled out as outflow boundaries (mini cold fronts) move out from thunderstorms to the north.  Thunderstorm coverage is expected to increase by Friday evening as the cold front moves closer to southern Wisconsin after 7pm/8pm.  Most of the active weather will remain to the north during the afternoon, but a few gusty wind producing storms could occur over northwest Illinois by the evening.  Moisture will also increase, leading to heavy rain producing thunderstorms.

Scattered thunderstorms remain likely for Saturday, becoming more isolated by Sunday as forcing in the atmosphere begins to weaken.  It'll remain humid, however, with temperatures in the upper 80's and the heat index reaching the upper 90's.

The weekend won't be a complete washout as there will likely only be a couple hours each day that you'll need to watch for storms.  Friday evening/night may be our best time for heavy downpours.