Introduction:
Wow! We have a lot to talk about this evening! Severe potential, including the risk for large to very large hail, damaging winds, and a couple of tornadoes, for tonight and tomorrow evening followed very quickly by snow day potential for Wednesday.
If there was ever a page in a textbook for Michigan weather, and how fast it can change, these next couple of days would certainly be included on said page! It was a very unseasonably warm day today with temperature across lower Michigan pushing 60 and we'll drop into the 20's by Wednesday morning!
Severe Weather Potential Overnight:
Prior to the primary severe weather risk tomorrow evening and overnight Tuesday we need to briefly contend with a low chance (5% Risk) for some extremely isolated large hail stones to fall during overnight thunderstorms.
This risk will be greatest over the thumb region of Michigan but does nonetheless include portions of southwestern and south-central lower Michigan. Persons in these areas tonight should be aware of the potential for large hail through 7:00 AM tomorrow.
Severe Weather Potential Tuesday Evening & Overnight:
We've been focused on this potential severe weather event for almost a week now. Typically, at this stage in the forecast, we have a pretty good idea of what to expect and there is little to no variability in the models. For whatever reason, that is not the case with this event. There continues to be a stark difference between the various computer weather models with regard to the timing of and potential hazards for this severe weather potential.
Before diving into our latest thoughts on this model variability, this is the latest Day 2 Outlook for Severe Weather from the NWS Storm Prediction Center. It remains largely unchanged when compared to this morning's Outlook, with the main difference being the small expansion of the yellow-shaded Slight Risk to the north to include areas along, and slightly north of the I-96 corridor.
One of the primary weather models shows storms arriving around 7:00 PM across southern lower Michigan complete with very clear indications of an all-hazards severe weather threat. A second model shows a much different solution with storms arriving closer to 10:00 PM with less of a clear severe weather threat and more disorganized storm mode.
These differences are due to the different predictions of the evolution of the atmospheric trough and the associated cold-front and wind dynamics it will bring with it. If the trough can speed up and bring mechanisms that force storm development across the region sooner then we will likely see a more potent severe event unfold. If, on the other hand, a slower progression of the trough occurs then we will likely avoid much of the severe weather potential.
The bottom line is that we still have a severe weather threat tomorrow, especially centered across southern lower Michigan, south of the I-94 corridor including the risk for large to very large hail, damaging winds, and tornadoes. We'll continue to watch the computer weather models and we'll be able to hopefully provide some more clarity on the timing and significance of this severe weather event. Please be #WeatherAware tomorrow and tune in to our live stream and social media posts for updates!
Snow, Cold Temperatures, and Chances For Snow Days Wednesday Morning:
The cold front that will cause the aforementioned thunderstorm development, and the associated severe weather threat, is a very strong one with a large temperature differential. This means that the temperatures ahead of the cold front will be well into the mid to upper 60's and perhaps even 70, while the temperatures behind the cold front will plunge into the mid to upper 20's.
This will cause a couple of things that will act to create at least some school closing potential for Wednesday morning.
Rain that falls during the thunderstorms on Tuesday evening into the overnight on Wednesday runs the risk of something called "Flash Freezing." This is when liquid water on the ground rapidly freezes to surfaces, such as pavement, and leads to very slick/icy conditions.
This cold front will prompt snow to develop over the lake and quickly propagate eastward over western lower Michigan. As much as 2-4 inches may fall by 9:00 AM, especially along the lakeshore and west of the US-131 corridor.
We will introduce a yellow-shaded "Minuscule (15-30% Chance) Risk" of school closings along the lakeshore to account for the combination of both of the aforementioned risks. Elsewhere, where snow will likely not arrive until after the conclusion of the school commute we will opt to only introduce a green-shaded "Predictability Too Low (<15% Chance)" of school closures.
We will likely need to make adjustments to this outlook for our Day 1 Outlook tomorrow evening. Severe weather and storm chasing will take priority over the creation of a new outlook discussion and graphic so if a Day 1 is not issued tomorrow evening that is the reason.
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