Metro Detroit weather: Breaking down thunderstorm chances every day this weekend

Severe weather possible Sunday

A view of Detroit, Mich., on May 17, 2019. (WDIV)

DETROIT – It’s definitely a cooler day than yesterday but, with the sunshine that some of us had (especially northern half of the area), it wasn’t all that bad of a day. Now it’s time to look ahead to the weekend. Mother Nature will cooperate for some of it, but not all, as we have a severe storm threat. Details below.

First of all, shower chances, and possibly even a thunderstorm, increase tonight as a warm front starts its move northward toward our area. Although all computer models suggest a dry evening for the Tigers game at Comerica Park, we are slightly concerned about some showers that have just developed over Lake Michigan that are moving east.

As a precaution, bring some rain gear with you to the game just in case those showers survive the trip across the state, but, at this point, we expect a dry evening and game.

Lows tonight will be in the upper 40s (9 degrees Celsius), but cooler to the north where lower dewpoint temperatures will allow temps to fall a little lower. Northeast winds won’t be a problem at 2 to 5 mph.

Scattered showers and possible thunderstorms Saturday morning should lift north of the area by noon, obviously, the farther south you are the earlier they end and the farther north you are the later they end.

Once the warm front passes by, we’ll see increasing sunshine that will boost temperatures into the low to mid 70s (22 to 23 degrees Celsius). Southeast wind at 5 to 10 mph will keep things cooler close to the big lakes.

Saturday evening and overnight will be quite and mild -- no weather problems there. In fact, temperatures will only drop into the low 60s (16 degrees Celsius) by Sunday morning!

Sunday is the day we need to keep an eye to the sky. An approaching cold front will trigger one or two lines of thunderstorms that will cross lower Michigan, but not until afternoon. Sunday morning looks pleasant and mild, so that’s the time to enjoy a nice walk or jog, or get in that round of golf. By mid-afternoon, however, the first line of storms should cross the area, and these storms could be severe.

It’s important to remember that severe weather situations are not created equal, and there’s some good news for us. Take a look at this image below:

This is the output from one of our computer models. The area circled is the projected wind speed and direction from the surface (bottom) to over 40,000 feet aloft. Think of those little icons as arrows, and notice that they are all point in roughly the same direction.

This means that there will be very little change in the wind’s direction above us, and this low “directional shear” means that we do not expect tornadoes. Rather, large hail and 60 mph straight line thunderstorm wind gusts appear to be the primary hazards, not to mention lightning.

A lot of you will be outdoors Sunday, and it is imperative that you stay up to date on the afternoon weather. Make sure that you have the free Local4Casters weather app downloaded on your phone…just search under “WDIV” in the app store. When you open the app, it opens right onto the radar page, which you can pan or zoom with your fingers. Check the app often for any developing storms, and remember that you also get warning notifications.

Also make sure that your weather radio is turned on and has fresh batteries. Finally, if skies are darkening and you’re starting to hear thunder or see lightning to the west, don't wait for the rain before heading inside.The most dangerous wind gusts associated with most severe thunderstorms rush out ahead of the storm, and arrive before the rain. If you wait for the rain, it’ll be too late.  Plus, if you see lightning or hear thunder, then lightning is close enough to hit you, no matter how far away it may seem.

One other concern for Sunday is the wind. It’ll become breezy, with southwest winds at 20 to 30 mph, and this will push the already high lake levels further inland than normal (as we’ve seen already multiple times this spring). So, those of you on the north and northeastern shores of our big lakes need to be on the alert for possible flooding on Sunday.

The only good thing about Sunday is that it’ll be a warm day (if you like your days warm), with highs near or even above 80 degrees (27 degrees Celsius).

A second line of storms is possible Sunday evening, and those could be strong to severe as well although, as we’ve seen many times in the past, the first line of storms could work over the atmosphere pretty good and deplete some of the instability needed for a second round of severe storms.

To help you plan, here is a series of maps showing you our RPM’s projection of rain and storm timing this weekend:

A quick look ahead to next week:

  • Monday: Mostly cloudy to partly cloudy, with highs in the mid 60s (18 degrees Celsius).
  • Tuesday: Partly cloudy, with highs in the mid 60s (18 degrees Celsius).
  • Wednesday: Mostly cloudy with some showers, and highs in the mid 70s (24 degrees Celsius).
  • Thursday: Partly cloudy, with highs near 80 degrees (27 degrees Celsius).
  • Friday: Partly cloudy with a chance of thunderstorms, and highs in the low 80s (28 degrees Celsius).

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