DETROIT – As I mentioned yesterday, there is a potential for an overnight severe weather event Wednesday night, and today’s new computer models suggest that some of the significant weather may impact part of our area.
Unlike the typical line of storms that accompanies an approaching front, this is a special cluster of storms that looks more like a big “blob” on a radar map. It’s called a Mesoscale Convective System (MCS), and what makes it really unique is that this particular type of storm cluster actually blows up at night, rather than in the heat of the day.
I don’t have time to get into all of its dynamics, but what generally happens is that, as the sun goes down, our surface wind decouples…you and I notice the diminishing wind here at ground level. However, those surface winds rise and strengthen the low-level jet (LLJ) aloft and, if it’s a particularly strong south or southwesterly LLJ, that pumps tremendous amounts of moisture and heat northward. If that occurs at an east-to-west oriented frontal boundary (either a warm or stationary front), then these massive clusters of storms can develop. If the winds aloft remain favorable (its direction veering with height, and wind speeds remaining strong), then this large cluster of storms can become a large cluster of severe storms.
The devil is in the details when we talk about an MCS, and I’d really like to get a look at Wednesday’s upper air data and high-resolution models before trying to get real specific with its orientation. But since today is Tuesday and many of you are already concerned about this, I’ll take a stab at some details using the high-resolution RPM model at my disposal (I also want to see what the 3km HRRR model shows…but that won’t be available until tomorrow afternoon). REMEMBER: THESE DETAILS CAN CHANGE, SO CHECK BACK WITH ME TOMORROW FOR AN IMPORTANT UPDATE.
First things first: we have no weather problems tonight. Expect mostly clear skies with a brief, spotty late-evening shower possible well north of I-69 (most won’t see one). Lows in the upper 50s to near 60° (that’s 15° Celsius for our Canadian friends). Wind quickly diminishing to a light northwest wind. Tonight’s sunset is at 9:13 PM.
Mostly sunny to start our Wednesday…no weather problems for the morning rush hour. Clouds will increase during the afternoon, but it should be dry for most of us (there’s only a very small chance for a late afternoon shower or thunderstorm). Highs near 80° (27° Celsius). Wind becoming south at 5 to 10 mph. Wednesday’s sunrise is at 5:57 AM, and Wednesday’s sunset is at 9:14 PM.
Wednesday night is the timeframe for our severe weather potential. Outside of a spotty shower, the evening should be relatively quiet. In fact, there won’t be much happening when most of us go to bed.
The MCS I talked about above should affect us in the middle of the night. It’s important to remember that where it tracks is dependent upon where it originates, as MCSs tend to follow what are called Corfidi Vectors (kind of like a train is guided around a curve by the track it rolls on).
The models give me a pretty good handle on the motion; it’s the initiation location that we need to nail down. Based upon the RPM (and another model not shown here, the 4km NAM), it appears that the biggest severe weather threat is generally south of 8 Mile, and more likely southwest of a line from Monroe to Ann Arbor to Lansing.
Expect torrential rain (the rain alone would wake you up), an amazing lightning show, potentially damaging wind, and possibly even a tornado, although the primary severe threat with an MCS is straight-line severe wind gusts.
By 6:00 AM, the MCS is gone, although the RPM shows another batch of storms for the farther northern suburbs. However, the 4km NAM doesn’t show this at all, so I’m not as clear about this threat, although I do expect some lingering showers and possible thunderstorms first thing Thursday morning.
All rain should be gone by late morning, and we’ll see improving weather through the afternoon. Highs Thursday in the upper 70s (26° Celsius).
Don’t forget that today (Tuesday) is our second Weather Radio Campaign Day for the 2016 season.
Ben Bailey will be out at the ABC Warehouse in Southgate this afternoon, where you can buy your weather radio and also have it programmed to just warn you for the county or counties you want to be warned for. Remember that, during our campaign, you can buy a weather radio at a significant Local 4 discounted price…only $29.99. Since we began our campaign five years ago, between 35,000 and 40,000 radios have been purchased here in metro Detroit.
I consider this the most important public service campaign we’ve ever done here at Local 4. Remember that every home, school, place of business, and house of worship should have a weather radio. If the power goes out and the cell system goes down, this little radio could be the only warning left that can save your life. We hope to see you in Southgate today but, if you can’t make it, the radios can be purchased at ANY ABC Warehouse or Meijer store at the discounted price.
Also remember to download the FREE Local4Casters weather app…when you open the app, it opens right to the radar page, so you can track the storm development Wednesday evening right in the palm of your hand.
And finally, follow me on Twitter (@PGLocal4) -- I tweet updates when it’s important. And tomorrow night, I think there’ll be a need to.
Lost in all of this (justified) talk about the Wednesday night severe weather is the fact that we desperately need some rain around here.
While conditions vary across the area, of course, Metro Airport has only received 0.24” of rain since June 6th…and that won’t get the job done. It would be great to not get the severe weather and “just” get some soaking thunderstorms (remember that lightning is good for our plants…it ionizes nitrogen in the atmosphere, so it’s literally “raining fertilizer”).
Friday and Saturday look like perfect summer days for GM Riverfest -- come on downtown and join in on the fun! We’ll have plentiful sunshine both days, with highs in low 80s (28° Celsius) Friday, and mid 80s (30° Celsius) on Saturday. Overnight lows will be near 60° (16° Celsius) Friday night, and then back up into the mid to upper 60s (19° Celsius) Saturday night.
Sunday should start dry, and it’s going to be a warmer and more humid day. Some thunderstorms are possible by mid to late afternoon, with highs in the upper 80s to near 90° (32° Celsius).
And what about the Ford Fireworks on Monday? The Sunday night cold front could extend a few showers into Monday morning, but I think things will dry out during the day, leaving us with spectacular weather for the big show! Of course you already know that Local 4 is the exclusive station that brings you the entire evening live from the comfort of your living room.
So join us downtown, on Local 4, or on ClickOnDetroit.com for all the excitement!