Major Severe Weather Chance in Great Lakes Region Today

I’m going to keep this post as short and sweet as possible! But a major severe weather threat will impact our region today. It’s ironic because, originally, the threat didn’t look that great. But, many different mesoscale and microscale features have changed to make this a viable threat (which is crazy considering my blog post yesterday was about the 2004 Utica Tornado which occurred on a day that conditions changed fast)

A MCS is presently ongoing that poses a high chance of becoming a derecho (a long lived severe thunderstorm line that travels several hundred miles that produces severe wind and tornadoes along its path). The storm system is just now clearing the Quad Cities and is racing into Northern Illinois. This line could affect the Chicago Metro area by 3:30 PM Central Time before racing our over Lake Michigan. Once in Southwest Michigan, the storms will have lots of instability to play with but will lose their steam as they enter Central Michigan and potentially move away from better dynamics. They still have a a good chance at being severe at that time. Note the storm reports thus far. Lots of wind reports, some in excess of 95 mph.

The SPC Forecast is below. Note that a Moderate Risk is in place across much of Illinois. The Enhanced Risk stretches into SW Michigan with a Slight surrounding it. I don’t want you getting caught in the semantics of “what risk area am I in?”. This can consistently change and this is an on-going situation. No matter what risk level you are in, you have a chance or being affected by this possible derecho. Have a way to get warnings and then heed all warnings.

The SPC Forecasts for Tornado, Wind and Hail are below. Note that hail won’t be too large of a thread but still something to watch. The tornado threat is there (and while there is an ongoing warning for a tornado in the system, one hasn’t been produced yet) but it isn’t our main threat. Wind is the major threat here, and this is shown by the “hatched” area on the forecast. This denotes where “significant severe wind” could occur. Once again, don’t get caught in the semantics of “where am I compared to the percentages”. Anything is always possible. We’re talking the potential for some places to see winds in excess of 100 mph.

Finally, here are some graphics from NWS Chicago and NWS Grand Rapids. These storms are moving quick and will hopefully move out fast. Stay tuned to Facebook, Twitter and your local NWS office for updates.

Adventure Brett (Forecaster Brett)

P.S. Check out the crazy hazard wording for the watch for Northern Illinois. Also attached is a corresponding Mesoscale Discussion