Holiday weekend includes potential severe storm threat

Paul Gross has latest Metro Detroit weather forecast

DETROIT – Sunshine has been slowly building into the area this afternoon, which made for a pleasant end of what turned out to be a pretty crummy workweek. A few showers are heading this way, and some of us will get a bit of rain in the middle of the night, probably arriving in our West Zone around midnight, and ending around 4 a.m. Lows will be in the mid-50s, with a light and variable wind.

Here is how our in-house RPM model is handling our weekend weather.

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Saturday looks to be a partly cloudy day, and the sunshine will boost highs into the mid-70s (24 degrees Celsius). Wind will blow from the south-southeast at 3 to 6 mph. Saturday is also the first day of Ramadan.  Many of our Muslim friends will be fasting between sunrise and sunset, which occur at 6:02 a.m. and 8:59 p.m., respectively. For those of you observing, I wish you a special, reflective Holy Month.

Partly cloudy skies should hold Saturday night, with lows in the upper 50s (14-15 degrees Celsius).

I have both good news and bad news for our Sunday. The good news is that any rain we get may hold off until afternoon. If this timing holds, then perhaps we can get a pleasant morning out of the deal. The bad news is that a cold front approaches during the warmest part of the day, and that will trigger widespread thunderstorms during the afternoon.

The cold front is a solid trigger to generate the storms -- no uncertainty there. So I’ve been pouring over upper air forecast data (called forecast soundings) this afternoon, and it appears that we’ll have more than sufficient wind shear (a veering of the wind direction as you head up into the lower atmosphere), which is a necessary component for the most severe storms.

The big question is: Will we get unstable enough for parcels of surface air to rise violently enough? The forecast soundings suggest that's the case, but that’s not a slam dunk. There are many things that could impact that, such as cloud cover increasing quicker than expected (and thus lowering our high temperature), less moisture streaming in from the south, warmer temps aloft than expected, etc.

At this point, I feel that there is at least a risk for some severe storms due to the front’s perfect timing and the good wind shear. How warm we get will dictate how widespread the severe storms become: an isolated storm in the otherwise solid line of "regular" showers and storms, versus a more widespread line of severe storms.

Here’s the Storm Prediction Center’s severe storm risk areas for the upcoming weekend, and you’ll notice that they have us in the Marginal Risk area for Sunday. That’s due to the uncertainty I discussed above.

If you have outdoor plans, I strongly urge you to check the radar on the free Local4Casters app often.  If you’re one of the few people who don’t have the app yet, just search the app store under "WDIV." It’s right there. Also, those of you who follow me on Twitter (@PGLocal4) already know that I tweet personalized updates in situations like this, including radar loops.  If you don’t have Twitter yet, it’s easy to sign up an account and follow me.

Storms will end Sunday evening, with lows by Monday morning in the upper 50s (14-15 degrees Celsius).

Memorial Day still looks dry in the morning, which is great news for the parades! If you happen to be in the Farmington area, come on down to Grand River just east of Farmington Road and help me honor our military men and women who sacrificed so much so we can live the life we have. I’ll once again be co-emceeing the parade, which I consider a very high honor. Everything gets started at 10 a.m.

As for your holiday barbecues, a few scattered pop-up showers are possible by mid to late afternoon. Not everybody will necessarily get one, but some will. Highs should be in the low to mid-70s (23 degrees Celsius). Again, our app’s radar page (which you can zoom in or out of as much as you want) will help keep you ahead of the weather.

Heading up north this weekend? Here are some maps to help you plan your holiday getaway:

Tuesday and Wednesday look identical. There will perhaps be some sunshine to start the day, then some pop-up showers in the afternoon. Highs will be near 70 degrees (21 degrees Celsius).

It will be partly cloudy Thursday, with highs in the low to mid-70s (23 degrees Celsius).

Then, as I’ve been telling you all week long, the jet stream finally starts making its move to the north, and we get into some really nice late spring weather! Friday through Sunday all look mostly sunny right now (what awesome news for Detroit Grand Prix weekend), with highs in the mid-70s (24-25 degrees Celsius) on Friday and Saturday, and in the mid- to upper 70s (25-26 degrees Celsius) on Sunday.