SHOUTOUT TO PIVOTAL WEATHER FOR HAVING A GREAT PLACE TO GO AND RUN MODELS! IF YOU LOVE WEATHER, MAKE SURE YOU CHECK THEM OUT! The photos included here are from their model runs. (Photo above is from the Storm Prediction Center. This is their morning forecast, which may change as the day rolls on).
Good Afternoon all, and welcome to my first weather post. I didn’t get a post up yesterday simply because I was still working on the one that was supposed to go up today (about a trip to Paris, subscribe by entering your email to the right to make sure you get notified when it goes up). However, I have had to shelve that one because a weather situation that will unfold today moved today into the “weather” category. I was originally going to post this yesterday, but decided today would be best, simply because we’ll have a better idea of what may happen the day of versus the day before.
As I type, a longwave trough is sitting over the west with two subsynoptic-scale cyclones jutting into the ridging to the east. The cyclone that will affect the Great Lakes region is presently sitting over Iowa. We were expecting this cyclone to push east today, hence the reason SPC (Storm Prediction Center) had everyone from roughly I-69 in Michigan west towards the Quad Cities in Iowa/Illinois in a Marginal Risk for Severe Weather. At that time, a Marginal Risk was warranted as we weren’t entirely sure how things would unfold, some of the models were really varying from eachother. However, as we moved into yesterday afternoon, some of the models (notably HRRR) started showing stark differences to what we were seeing earlier in the day. This also weighed into my decision to wait and post until today, I wanted to see what SPC and the NWS (National Weather Service) offices in the Great Lakes Region were saying.
At any rate, this cyclone will cross into Illinois and weaken, pressing further east as a shortwave into Lower Michigan. Lower Michigan still has ridging (albeit weak) in place, giving the area fair weather for the majority of the day. However, scattered thunderstorms will begin to develop across East Iowa and Northwest Illinois into early afternoon. Models are showing broken arcs of scattered convection as the storms move northeastward into parts of Wisconsin. This is not the area we are focused on, the main area of focus will come later in the afternoon.
It is unknown if this early afternoon convection will work over the atmosphere too much. We also have the possibility of it laying down an outflow boundary, possibly helping to enhance any storms that ride the boundary later. As the storms start to form in Central Illinois (while remaining rather scattered), they will form as supercells that move to the northeast.
Now, here is what we can expect for the following areas (Note that I am using the HRRR model specifically because it paints a clearer picture compared to some of the other models when it comes to storm motion and mode. However, just like SPC and NWS, I have taken other models into consideration in the forecast, including GFS and NAM).
Northeast Illinois (including the Chicago Metro Area): As you can see in the photos below, storms will be on going at 20z (2 PM CDT, 3 PM EDT) across Northeast Illinois, with the supercells forming in Central Illinois. At this point, SigTor (Significant Tornado Parameters) sit above 1 for most of Central Illinois into parts of Northern Illinois (with an isolated value of 2.2 near the Peoria area). Values higher than 1 are environments in which EF2 or stronger tornadoes can occur (note the word CAN…this doesn’t mean they WILL occur). It just means the environment could favor those. This means we do have to keep an eye on this area to see how things evolve moving forward. SPC does have an Enhanced Risk out for this area, mostly because all storm modes are possible this afternoon, but the tornado risk has increased since the initial morning convective outlook.
As we move towards 22z (4 PM CDT, 5 PM EDT), you can see that the storms have progressed into the Chicago Metro area, still showcasing possible supercell characteristics (and still maintaining separation). Some models are showing these storms beginning to form into a line and pushing eastward into Indiana and Michigan. Either scenario is possible, but note that they will be pushing into dynamics not as favorable for severe weather the farther east they push (but later models and readings could also contradict that…I’ll wait until we get into the Indiana and Michigan zones for that). With that said, the SigTor values did drop a bit, but some are still over a 1. Some things to note is that a tornado is a tornado no matter what….they should be taken seriously no matter the environment. An EF0 and EF1 could cause injuries or more. The Supercell Composite readings (showing higher readings for supercell occurrence, with any hazard possible) are decently high across the area at this point, meaning some severe hail and wind is possible. Northern Illinois is a location where all hazards are certainly possible (tornadoes, severe wind and severe hail). By 01z (8 PM EDT, 7 PM CDT) the storms will have pushed over Lake Michigan, starting to shift into a more linear structure as they move into Northern Indiana and Southwest Michigan. What I want you to get out of this is the fact that Northern Illinois is the area that will have the best risk for severe weather this afternoon and evening.
Central Illinois (including the Peoria area): This area, and immediately to the north, are where the storms will initially fire. Facing many of the same hazards as Northern Illinois, just earlier on. They’ll move out of the area rather quickly as they intensify.
Southern Wisconsin (including Kenosha & Janesville): For the most part, the worst of the storms should stay south of you. But that doesn’t mean you won’t get some thunderboomers. Also, you are really close to the action and I don’t want to get stuck with semantics of “the storms will ONLY be in this area”. I think it is a good idea to keep an eye on the weather this afternoon, just in case the storms end up sneaking into the area. The dynamics aren’t the best, but we have seen some powerful storms on days where they weren’t expected. (like the Utica Tornado of 2004…which was going to be the topic of my first weather post, until this presented itself). It is the Midwest after all…
Northern Indiana/Southwest Michigan (including Gary, South Bend, South Haven and Kalamazoo Areas): Now, extreme Northwest Indiana (Gary area) is the only area that is in a Slight Risk. South Bend is in a Marginal and Michigan (with the exception of Berrien County) was left out of the risk area altogether. Considering the HRRR has had the storms move a bit quicker, I would say just keep an eye on the skies and your ears tuned to the media channels. Of course, the closer to Northern Illinois you are, the better chance of severe you have (as the storms will be ongoing). The storms are anticipated to be a weakening MCS or broken supercells as they move into Northern Indiana/Southern Michigan (note the HRRR run below). The system was expected to arrive much later. If it still does this, then the chance for severe weather in this area will be low. However, deep layer shear will be sufficient and models are trending towards instability building with the earlier arrival times. This is noticed in the HRRR model runs showing some SigTor values climbing across the region (at this point, I don’t think violent tornadoes will be the main concern, but some tornadoes could be. Hail and wind will be primary threats). Supercell composite continues to climb too. As you can see below, the storms will be in the Southwest Michigan area at 02z (9 PM EDT, 8 PM CDT). The farther east these storms move, the more they will weaken. Transitioning towards nighttime and the fact that things are much more stable in Eastern Michigan and the Ohio Valley means that the severe threat will wane. Parts of Northern Indiana and SW Michigan just need to keep an eye on things as the evening approaches. Its close enough that anything can happen. NWS highlights that the severe threat is low, but not zero….and we have seen SPC change forecasts for areas as things become more clear. Right now, I would expect thunderstorms with a chance they could still be severe. We’ll just have to see what the storms do in Northern Illinois.
Two things to remember before we end this post. One, heed all warnings. If a tornado warning is issued, go to an interior room on the lowest floor of your house. Find ways to protect yourself from flying debris. Remember, severe wind gusts can be destructive too. Stay away from windows and remain inside. Same goes for hail. Also, have a way to receive warnings!
Another thing to remember….this is a forecast based on models. Things can definitely change. We have seen some scenarios be much worse while some completely busted. Weather is still a hard thing to predict. Thunderstorms can be predicted, but how bad they will be is not a perfect science. These posts/forecasts are only to make people aware. This is not anything to get super concerned about, but it is always a good idea to have a plan in place, just in case! I will updating on Twitter (www.twitter.com/universeofadv) so feel free to follow there and get updated on the weather as it unfolds. It’s also a good idea to pay attention to the Storm Prediction Center as well as your local NWS office.
One more thing to note, this system will stall across the area and give a decent chance of thunderstorms for a good portion of the week. It is too early to know if some of the storms could become severe (but there is always a chance they could). As always, follow along on Twitter for updates there.
Until next time, “When clouds appear like towers, the Earth is refreshed by frequent showers”
Adventure Brett (or Forecaster Brett?)