Metro Detroit weather: Chance of torrential downpours, lightning during Grand Prix

Mostly clear Friday night

By Paul Gross - Meteorologist

DETROIT - It’s been a beautiful Free Prix Day on Belle Isle, as expected. But if you’ll be heading to the island Saturday afternoon, you’d better read the rest of this article carefully, and share it with family and friends who might be going to the race.

First, tonight should be a fairly quiet night. It’ll be mostly clear overall, although some clouds may pass by periodically. The only chance for a shower is the northern Thumb, as the remnants of a decaying area of thunderstorms to our west may just graze that area. But for most of us, it’ll be dry, with lows in the low 60s (16 to 17 degrees Celsius).

Saturday will start with some sunshine. It’ll be a nice start to the day. So if you have to choose any part of the day for some outdoor plans, that’s the part to plan on.

Thunderstorms will develop during the afternoon, and there will be torrential downpours and a lot of lightning with these storms. A few of the storms could have large hail, and strong wind gusts.

If dangerous weather approaches Belle Isle, then announcements will be made, and everybody will need to catch those shuttles back to Cobo or the Ren Cen for shelter.

We cannot strongly enough recommend that everybody have our free Local4Casters weather app, and check the radar often (when you open the app, it opens right to the radar page). Just go to the app store and search under “WDIV." You’ll see our weather app right there.

There is no excuse not to have it, especially if you will be outdoors Saturday afternoon, and if you’ll be at the race, you really need to stay ahead of the weather because there will probably be a crush of people all trying to get off the island at the same time should dangerous weather approach.

Highs Saturday will reach the upper 70s to near 80 degrees (26 to 27 degrees Celsius), depending upon what time the clouds move in. Wind will blow from the southwest at 10 to 15 mph. Our in-house high resolution model, called the RPM, suggests that we may have a break from the storms late afternoon into the early evening, before another batch of storms moves in.

However, another high-resolution model, called the HRRR, maintains a continuous storm threat through late evening. Hopefully, new models runs this evening and tomorrow morning will allow us to nail down this aspect of the forecast.

Then a cold front will sweep across the area Saturday night, and sweep the storms right out of here.  We’ll be dry by dawn Sunday, with lows in the mid 50s (13 degrees Celsius).

Partly cloudy, much cooler and breezy on Sunday, with highs only in the upper 60s (20 degrees Celsius). It sure won’t feel like an early June day, but at least it’ll be dry on Belle Isle. Don’t forget the sunscreen. The sun’s rays are very potent right now, and those rays will burn you just as quickly as if the temperature was in the 80s.

Next week

Mostly sunny on Monday, with highs in the mid 60s (18 degrees Celsius). At least wind will be light, so it’ll still be a pleasant day. Just not as warm as you’d like if the pool is in your plans.

Partly cloudy on Tuesday, with highs in the mid 70s (23 degrees Celsius).

Mostly cloudy with a chance of showers and thunderstorms on Wednesday, with highs in the upper 70s (26 degrees Celsius).

Mostly cloudy on Thursday, with highs in the mid 70s (25 degrees Celsius).

Partly cloudy on Friday, with highs in the upper 70s (26 degrees Celsius).

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