This is like a broken record theme in the past two weeks, but it is springtime I guess, and parts of the United States are settling into a rather unsettled pattern. But, alas, here we are again. Severe weather is possible for parts of the Great Lakes Region, but we are only in a Marginal Risk by the Storm Prediction Center at the moment.
Now, there are a lot of reasons why many parts of the region were upgraded from general thunderstorms to a marginal risk. One is the fact that models are showing a splendid setup for severe weather. MUCAPE will approach 3000 j/kg for most of the area, a 30 knot low level jet is nosing in from the west (which you can really see on the hodographs as they are curving well), 40 knots of bulk shear at the 0-6km layer and mid-level winds at 50 knots roughly from the northwest.
However, you may ask yourself “Why only a marginal risk then?”. That is what we will dive into here and it won’t take long to explain. First, we were upgraded to a Marginal Risk based off of the factors I stated above. If things get to that level, then we could definitely see some rather potent severe storms. However, there are some microscale negating factors that could change all of the above, or at least not let us reach that potential (I’m always saying these systems are constantly evolving, and today proves that).
There is a slight risk for parts of the Ozarks, but we aren’t focusing on that region today. The best chance for severe weather in our region will be from Milwaukee, down to Central Illinois and then over into Southwest Michigan (spreading east from there). Northern Indiana and Northwest Ohio I’ll include too, but that all hinges on what happens upstream. At this moment, a line of strong thunderstorms have moved through the Milwaukee area and out over Lake Michigan. These storms are along a shortwave that will be moving across Lower Michigan this afternoon. This means that the area from that area of Wisconsin into where these storms are moving could end up working over the atmosphere to where it won’t be able to recover for prime conditions later this afternoon into the evening. This means Northern Indiana and parts of the Chicago Metro area would see a slightly higher chance.
But, playing devils advocate here, some models are showing this line of storms dissipating completely as they move on shore. As I type though, they are strengthening a bit. So, we’ll have to watch this line and see what it does to see how Michigan’s threat will play out. It may have already worked over Wisconsin and that is why they are barely in the threat area, but that doesn’t mean they are completely out of the woods. The shortwave will move through either way, so we’ll just have to see how our temps, dew points, CAPE and all of the other parameters later this afternoon end up looking. We’ll have to look at each microscale environment and we may not know the full picture until 30 minutes or so before storms begin to fire (if they fire at all). Also, I wouldn’t rule out the possibility of a severe gust (as well as maybe some hail approaching severe limits) as the line of storms associated with the shortwave moves through Michigan. No such reports have come out of Wisconsin this morning, but they do appear to be strengthening as I stated.
The second negating factor more so applies to Michigan and Michigan alone. Surface winds are fairly strong out of the west which, with the shape of the lakeshore, leads to a divergent wind. This draws in air that is sitting over the lake that will try to keep the atmosphere stable. Once again, there is no way to tell if the wind will end up divergent or not until after this shortwave moves through. While it appears it may be, some areas under the influence of the lake-modified air will not be able to get initiation going. This could also hinder development downstream. Just something else to keep an eye on.
Overall threats for any storms that should form will be some damaging wind gusts and large hail. Looking at hodographs and the way the models are laid out, I would expect hail to be one of the largest threats, but it depends on how storm mode works. Supercell composite values are a bit high, but definitely not the highest we’ve seen them this year (looking back at the Michigan Hail Event in April). While a tornado can’t be ruled out, the numbers aren’t sitting too high for that. Some Significant Tornado Parameter values approach 1 in parts of Michigan and Indiana, which leads to the credibility that tornadoes may be possible, but not super likely (and if they do occur, they’ll be generally weak in nature, but you still have to heed warnings with them). SPC reflects that with a “Less than 2% for all areas” tornado outlook today.
One thing I want everyone to remember, once again, is that this is an ever-evolving situation. Small scale changes could increase the risk. It’s just something we’ll have to keep an eye on. If any major changes in outlooks occur, I’ll post updates below. Otherwise, follow along on Twitter to see all of the updates from area NWS Offices.
Also, we’ll enter into a rather quiet weather pattern for a bit, though a nasty system may approach from the west as we head into next week. Then we have to worry about what is left of Cristobal next week as the storm moves into the United States and, eventually, becomes Extratropical. We’ll get tropical moisture from it as well as a wind and heavy rain threat. We do not know exactly where Cristobal will go yet, it isn’t even supposed to make landfall (projecting Louisiana) until very early Monday morning as a Tropical Storm. It wouldn’t move up into the Great Lakes Region until Wednesday at the earliest (and by the time it even reaches Michigan, it may still be a Tropical Depression, so areas may be seeing a strong tropical system still), and the path is unknown as this time that far out. It’s anyone’s guess. But if it threatens, you know you’ll be able to read about it here!
Until tomorrow, “When clouds appear like towers, the Earth is refreshed by frequent showers”
Adventure Brett (or Forecaster Brett?)
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