Tornadic Storms Expected Over Illinois Indiana Today/Tonight, Great Lakes Howler

Written by on November 17, 2013 in United States of America with 0 Comments

We have a dangerous severe weather situation unfolding this afternoon and tonight over the Ohio Valley as a deepening surface low pushes northeast over the Great Lakes with warm, moist air flowing up from the Gulf as well as the Atlantic while cold, arctic air flows out of the northwest, on the backside of the low. A strong 70kt low level jet will split the growing temperature contract along the cold front, helping increase the upward motion within the warm sector and front right quadrant of the jet. Area of maximum lift!

The dangerous aspect comes together as the core of the intensifying surface low pushes up through eastern Iowa and western Illinois into the lower Great Lakes with all the ingredients converging late this afternoon just a little further east over eastern Illinois and Indiana. Powerful storms will erupt along and ahead of the CF but strong shear or varying winds with height will help create spin within these likely, explosice thunderstorms and so there’s a high risk of not only damaging wind gusts along a squall line but large hail, dangerous lightning and of course tornadoes.

Below is the risk map from the SPC and you can see a rare HIGH RISK area over eastern Illinois and much of Indiana.


The below GFS 500mb upper level chart shows the intense upper winds rounding the southeast side of the low and trough late this evening. Where you can see the reds, expect some very intense low level, damaging winds and the greatest risk of tornadoes.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

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Here’s the 21 hr GFS surface chart which shows a 984mb low spinning over Lake Michigan. While plenty of heavy rain lifts north over the Ohio Valley, you can see a fresh push of cold arctic air into the Northern Plains on the backside of the system.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Check out the 48 hour QPF rainfall.


By 36 hrs that low has deepened to 968mb to the south of James Bay. Note the very tightly packed isobars, so this storm will become another impressive wind machine for the Great Lakes and widely across Ontario and Ontario tonight and especially tomorrow.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Also notice the rain band and potential squall line pushing through the I-95 corridor tomorrow morning. This could present a trouble AM commute to the Big Cities.

As well as widespread gales and cold NW winds with potential lake-effect snow, check out the below wave heights anticipated Monday morning.


As mentioned already, this system could bring a decent fresh snowfall to parts of northern Ontario with cold air wrapping on the backside of this deep system.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Following a mild, damp weekend across the Northeast, another brief blast of colder air pushes in as the low lifts up into Labrador.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

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