Metro Detroit weather: Storms, heat and humidity
Small chance for overnight thunderstorm
DETROIT – If you’ve been watching the radar on our Local4Casters app (you can download it for free from the app store. Just search under “WDIV”), you saw a massive area of thunderstorms approaching Lake Michigan Thursday morning. It indeed looked ominous.
But it doesn’t look nearly as impressive now as it did earlier, which is counterintuitive to many of you. Why is it weaker now, during the hottest part of the day, than when it was cooler? Because this is a specific type of thunderstorm cluster called a mesoscale convective system (MCS). They blow up at night as the low level jet stream (LLJ) strengthens -- this fuels the system and keeps it going all night.
Then, when the LLJ starts weakening as the day progresses, the batch of storms becomes less organized. Sometimes, the entire massive cluster of storms is gone within a few hours. So, while some thunderstorms are possible across Southeast Michigan this afternoon, and a few could become severe with strong wind gusts, don’t expect anything resembling what the radar looked like earlier.
There’s only the small chance for an overnight thunderstorm, so we shouldn’t get rocked out of bed tonight. However, the heat is on, so is the humidity, and it’s only going to get a lot worse over the next two days.
Humid air does not cool nearly as well as dry air, so lows tonight will only fall into the upper 70s (26 degrees Celsius), and remember that it’ll take all night to get there. We’ll be in the 80s most of the night. Not surprisingly, the National Weather Service has issued an Excessive Heat Warning until 8:00 p.m. Saturday.
Friday (TGIF!) will be dangerously hot and humid, with afternoon highs reaching the mid to upper 90s (35 to 37 degrees Celsius), and the humidity making it feel like 105 to 110 degrees (41 to 43 degrees Celsius). Scattered thunderstorms are possible once again. The best chance during the first half of the day appears to be near and north of I-69, with chances farther south later in the day.
Generally speaking, the farther south you are, the lower your thunderstorm risk. But any storm that does pop up, especially in the afternoon, could have strong wind gusts, so keep an eye on things on our app’s radar.
The sunshine and high heat and humidity also means that Friday will be another Ozone Action Day. Believe it or not, there are a few common sense things you can do that actually make a tremendous difference in reducing the emissions that are turned into ozone by the sunshine, heat and humidity:
Friday’s sunrise is at 6:14 a.m., and Friday’s sunset is at 9:05 p.m.
Warm and oppressively muggy Friday night, with lows in the upper 70s to near 80 degrees (26 to 27 degrees Celsius). By the way, we’re keeping a very close eye on that overnight low:Tthere have only been three occasions in recorded Detroit weather history in which an overnight low has not dropped below 80 degrees (27 degrees Celsius). We’ll be very close to that dubious achievement.
Dangerously hot and humid once again on Saturday, with another thunderstorm chance. Highs in the mid-to-upper 90s (35 to 37 degrees Celsius), with the humidity making it feel like 105 to 110 degrees (41 to 43 degrees Celsius).
Now for some good news: A cold front with substantial relief will approach either Saturday night or Sunday morning. Shower and thunderstorm chances continue ahead of the front, and then taper off behind it. It’s not clear how long the rain chance will extend into Sunday. We’ll try to get more specific about that tomorrow.
However, after another oppressively warm and muggy Saturday night, we should start noticing some relief from the heat and humidity by later in the day Sunday. In fact, if the front moves through quickly enough, we could even salvage Sunday afternoon, with highs in the mid 80s (29 to 30 degrees Celsius).
As mentioned yesterday, it appears that we’ll then have a spectacular stretch of summer weather all next week.
In case you missed them yesterday, here are some heat wave tips that will really help:
Heat stroke occurs when our internal body temperature rises to an unsafe level -- above 105° (41° Celsius). If you notice somebody in the heat exhibiting the following symptoms, call 911 immediately:
- Hot, dry skin (no sweating), despite the heat. The skin may also be red.
- Severe headache or dizziness
- Nausea and/or vomiting
- General weakness or severe muscle cramps
- Loss of consciousness
- Rapid heartbeat and rapid, shallow breathing
After calling 911, start first aid which, in this case, is simply trying to cool the person. If possible, put them in a tub of cool water. If that’s not possible, dampen their skin and fan them, or sponge them with cool water.
You can even use the cool water from a garden hose. Another very effective thing to do is putting ice packs under the armpits and in the groin area.
It’s vitally important to get the person’s core body temperature down as best you can until the EMS arrives. Even just moving them into some air conditioning helps. At the very minimum, at least get them into the shade.
If you know any elderly people who live without air conditioning, or somebody with very young children, please check on them when we hit the peak of this heat wave.
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