Tuesday severe weather update for northern Illinois

 

11:45PM UPDATE: Our severe threat has pretty much ended this evening, but there still remains a few thunderstorms moving across northern Illinois. The biggest impacts will be heavy rainfall, frequent lightning and perhaps some small hail. The severe thunderstorm watch has been canceled.

6PM UPDATE: A SEVERE THUNDERSTORM WATCH has been issued for all of northern Illinois and southern Wisconsin until Midnight. We are beginning to see storms fire up along a warm front, near I-80, this evening. The expectation is for these storms to grow and shift north, north of the warm front over the next couple of hours. As they do, they will become elevated posing a risk for large, perhaps destructive, hail. Strong wind gusts may also occur with any storm. We should see storms expand into our region within the next hour or two.

PREVIOUS DISCUSSION: A warm front continues to strengthen south of the immediate viewing area where temperatures are currently in the 70s and dew points in the 60s. North of the front, which is where we sit, it is quite a bit cooler with a chilly breeze from the northeast and temperatures in the 40s. This will play a role in what types of severe weather everyone will experience through the evening and early overnight.

Not much has changed locally as the risk for supercells with large hail remain our biggest threat. It's likely we'll see a tornado watch issued late this afternoon/early evening for those locations along and south of the warm front, which right now is currently along the I-80 corridor. There, tornadoes are the greatest concern along with damaging winds and large hail.

Further to the north our threat remains large hail as any storm that develops north of the front will become elevated, feeding off instability that increases a few thousand feet above the surface. I know it may be hard to think about severe storms when we have been stuck in the fog, low clouds, and chilly conditions. We may see a few isolated showers/storms between now and 6pm, but thunderstorm activity should increase between 6pm and 7pm, becoming more scattered through the late evening.

While the highest tornado threat remains to our south, we'll be keeping a close eye on any storms that develop in our far southern counties for a small tornado risk, especially if the boundary drifts back north later this evening.