Source NBC Chicago

A severe thunderstorm watch was issued for much of the Chicago area Friday and will last for several hours, bringing with it much uncertainty. With much of the Chicago area already under a severe weather alert as an intensifying line of storms races toward northern Illinois, what can you expect and when as Memorial Day weekend begins? A severe thunderstorm watch was issued for much of the Chicago area Friday and will last for several hours, bringing with it much uncertainty.

Here's a look at what to know about the forecast:

Friday morning All of northern Illinois was placed under a severe thunderstorm watch until 1 p.m., according to the Storm Prediction Center. The National Weather Service warned around 6:45 a.m. that a line of severe storms would move into northern Illinois "within the next few hours" and that line carries with it the threat for damaging winds, large hail, and possibly tornadoes. The biggest threat will take place through 9 a.m. in areas along and west of Interstate 39, however. "Have multiple ways to get warnings," NWS tweeted.