Metro Detroit weather: Tracking high heat, severe storm chances tonight

Plus, early look at Labor Day weekend weather


It’s been another sweltering day, with heat indices between 95 and 100 degrees (35 to 38 degrees Celsius), although not everybody shared in the wealth…the northern half of the area held onto more cloud cover, which kept temperatures lower.  

Although a few showers crossed the area, most of us haven’t seen any meaningful rain during the day.

Of greater concern is a line of thunderstorms that will develop west of Lake Michigan and move eastward during the night.  Some of you have been asking us about a sensationalistic, clickbait headline on the internet today, which said that a “new weather term could hit Michigan tonight.”  

That term is quasi-linear convective system (or QLCS), and we want to assure you that the term is not new, and it is not some once-every-1000-years type of Armageddon storm that will destroy humanity.  Is a QLCS dangerous?  

Of course it is…it’s a line of severe storms that cause damage. Sometimes lots of it. But a derecho, which we’ve written about in the past, is a much more dangerous line of super-severe wind damage that affects a much larger area.


What's a QLCS?

A QLCS is a line of severe storms, but with curves and waves in it.  Thus, the term “quasi-linear.”  The importance of this type of line of storms is that localized wind shear created by wind flowing out ahead of the storms in areas where there are curls or bows can spin up brief, weak tornadoes.  

They happen so quickly and have such short lifespans that they sometimes happen before a tornado warning can even be issued.  That’s why we meteorologists spend so much time explaining the radar whenever a QLCS approaches the area.  

Tuesday night severe weather chances

Alright, about tonight’s weather.  A potent line of severe storms (yes, a QLCS) will move out of Wisconsin into western and central Michigan tonight.  These storms will be initially severe when they cross Lake Michigan, but then start to weaken during the night as they move eastward.  

Large hail and damaging wind gusts are the primary hazard, with a much, much smaller risk for a small, brief tornado.  

While those of you in the Thumb may get some of this severe weather, chances start dropping as you head farther south…especially south of M-59.  We’re not saying that chances there are zero, but that it’s unlikely compared to the risk for those in the rest of the lower peninsula north and west of here.

Here’s a series of maps showing you the progression of weather out ahead of the cold front, which will eventually cross the state on Wednesday.  Notice how that line of storms weakens tonight as it progresses eastward:


Wednesday weather

The steamy air mass will stick around through Wednesday afternoon.  Lows tonight will once again be in the mid 70s (23 to 24 degrees Celsius).  By the way, unless we drop below it before midnight, this morning’s low of 76 degrees (24 degrees Celsius) broke today’s old warmest record low temp of 74 degrees (23 degrees Celsius), set back in 1977.

Wednesday will feature scattered showers and thunderstorms.  Cloud cover will limit highs to the mid 80s (29 degrees Celsius), but it’ll still be steamy out.  Southwest winds at 10 to 20 mph will shift to the west by late afternoon after the cold front moves through.

Wednesday’s sunrise is at 6:55 a.m., and Wednesday’s sunset is at 8:12 p.m.

Decreasing clouds Wednesday night, and you’ll notice the cooler, drier air moving in!  Open up the windows, as lows drop to near 60 degrees (15 degrees Celsius) in our Urban Heat Island closer to Detroit, and down into the 50s (12 to 14 degrees Celsius) in rural areas.

Thursday weather

Partly cloudy and much cooler on Thursday, with highs in the mid 70s (23 degrees Celsius).  Some of you in the Thumb may struggle to reach 70 degrees (21 degrees Celsius).

Mostly clear Thursday night, with lows in the 50s (10 to 14 degrees Celsius).

Friday weather

Mostly sunny on Friday…can’t ask for a better day to head over to Arts, Beats & Eats in Royal Oak!

Highs in the upper 70s (26 degrees Celsius) will be accompanied by low humidity.

Labor Day weekend

A warmer, more humid air mass will return to start the holiday weekend, and the transition from Friday’s cooler, drier air mass means that showers and thunderstorms are possible Saturday…but probably not until afternoon.  Highs should reach the mid 80s (29 to 30 degrees Celsius), and you’ll notice the humidity coming back up.

We can’t rule out a shower or thunderstorm Saturday night, with muggy lows in the upper 60s (20 degrees Celsius).

Partly cloudy on Sunday and Monday with just a scattered shower or thunderstorms possible…more of these two days should be dry than wet.  Sticky highs again in the mid 80s (29 to 30 degrees Celsius), with muggy overnight lows in the upper 60s (20 degrees Celsius).

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