Monday Severe Weather Update

10:25pm Update: All severe thunderstorm watches and warnings are done for the night, but a Flash Flood Warning will continue for Winnebago, Ogle, and Lee until 1:30am and Stephenson, Carroll, and Whiteside until 2:30am.

9:30pm Update: All warnings have been allowed to expire for the Stateline. Here's a look at some of the storm reports we've received from this evening's second round of storms.

Amboy: Nickel-size hail and downed trees.
Rockford Airport: 56mph wind gust.

8:55pm Update: Severe T-Storm Warning for E Boone, McHenry, DeKalb, and E Lee until 9:30pm. 60mph winds & quarter-sized hail possible.

8:40pm Update: Severe T-Storm Warning for S Winnebago, S Boone, NW DeKalb, Lee, and Ogle until 9:15pm. Warning includes the city of Rockford. Storms capable of 60mph winds and quarter-size hail, especially in Ogle County.

7:40pm Update: No watches or warnings are in effect at the moment. More storms are moving in from the west, but any severe threat should stay closer to the Quad Cities.

7:00pm Update: Our power is back on at the station! Sorry for the inconvenience. Here's the latest. A Severe T-Storm Watch continues for McHenry until 9:00pm, but the storms that prompted this evening's watches and warnings are now pushing east and out of the viewing area. A few storms will still be possible through midnight, but the severe threat looks minimal for the rest of the night.

5:15pm Update: Severe T-Storm Warning for Rock and Walworth until 6:00pm. 60mph winds and penny-size hail possible.

Line of storms moving through southern Wisconsin and north-central Illinois moving east/northeast between 45-50 mph.  Here's a list of cities that will be impacted as this line of storms continues to move through.  Seek shelter, away from windows as storm winds could reach 70 mph.

Severe Thunderstorm Warning for Green and Rock counties in southern Wisconsin until 5:15pm.  Storm is currently in western Green County just west of Monroe and moving northeast at 50 mph.

Severe Thunderstorm Warning for Jo Daviess, Carroll and Whiteside counties until 4:30pm.  Storm is moving to the northeast at 85 mph!  Storm will be capable of producing winds in excess of 70 mph. 

3:35pm Update: A Severe T-Storm Watch is now in effect for Walworth (WI) and McHenry (IL) until 9:00pm. Tornado Watch continues for the rest of the Stateline until 7:00pm.

Tornado Watch issued for most of northern Illinois and southern Wisconsin through 7pm this evening.  Counties included: Green & Rock counties in southern Wisconsin and Jo Daviess, Stephenson, Carroll, Whiteside, Winnebago, Boone, Ogle, Lee and DeKalb counties until 7pm








1:30pm Update: A line of thunderstorms has started to develop in central Iowa and will begin to gain a little more forward speed as they move into eastern Iowa.  Right now, there are no active watches or warnings out for northern Illinois or southern Wisconsin, but that will likely change as we head into the afternoon.  Timing of storms looks pretty much on as to what we've been saying throughout the morning:  north-central Illinois and southern Wisconsin between 3pm and 6pm, extending out towards Chicago after 8pm. 

Should storms gain forward speed as they move through Iowa, they will be moving fairly quickly at speeds roughly around 60mph.  This would mean that there wouldn't be a lot of time to react if a warning were issued.  Now is the time to have a plan in place for severe weather.  Know where to go if a warning is issued for your county. 

We'll continue with further updates throughout the afternoon as needed.



1:00pm Update:  Weather briefing with the Chicago National Weather Service is about to begin shortly.  Will provide updates throughout the conference call.


Mid-morning weather analysis:

There remains a decent amount of cloud cover in northern Illinois and southern Wisconsin this morning, but looking at the most recent visible satellite image shows some clearing beginning to take place further west.  The weather and skies will remain quiet through at least early afternoon as the atmosphere will need some time to 'recharge' after last night's thunderstorms.  Thunderstorms have redeveloped back west in Nebraska and western Iowa closer to a cold front, outflow boundaries and low pressure.  The image on the left is a look at the CAPE, Convective Available Potential Energy, within the atmosphere.  This is how much 'energy' the atmosphere has to work with when generating thunderstorms.  Right now, the greatest instability is to the south where thunderstorms have been lacking through the morning, however, thunderstorms have been riding just to the north of that axis and are currently moving east.

As we begin to peel away at the cloud cover through the afternoon, the instability is expected to rise further into Illinois and Wisconsin.  Right now, the greatest timing for storms appear to be between 3pm/4pm in eastern Iowa/northwest Illinois and 6pm in north-central Illinois.  The tornado threat will remain highest in Iowa as individual storms develop.  As the storms move east, they will form into a big cluster or even a strong line of storms with damaging winds becoming the main concern.  The storm threat will diminish after 11pm to the east as a cold front and low pressure move through.  The overall timing of thunderstorms for the Stateline looks to be roughly between 4pm and 11pm.  As storms continue to develop out west and clouds begin to slowly clear, we'll continue to provide updates throughout the day.

A Flash Flood Watch remains in effect for most of northern Illinois through Tuesday morning.

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Strong thunderstorms rolled through eastern Iowa and northern Illinois late Sunday night and early Monday morning producing anything from extremely heavy rain, damaging winds, tons of lightning and even tornadoes.  While we've got a little break from the activity early this morning, the thunderstorm threat will really ramp up going into the late afternoon and evening.

The Storm Prediction Center has highlighted northern Illinois and southern Wisconsin under  Moderate Risk for severe weather as it looks like things are coming together for a potentially significant damaging wind event rolling through the Stateline this evening and early overnight. 

I'm currently working on a complete analysis and will have a detailed update for you coming up shortly!