Why parts of SE Michigan didn’t get as much snow as expected in winter storm

There was a lot of interest in this week’s storm, not just here in southeast Michigan, but over the entire eastern half of the nation.

We missed out on the worst of it -- a massive ice storm extended from Texas all the way northeastward into parts of New York, and, south of there, a severe weather outbreak has generated at least two tornadoes in Alabama that caused damage. The airlines were besieged with a barrage of flight cancellations as a result.

But for us, on the colder side of the system, it was snow…but with widely varying amounts. Generally, the northwestern half of our area received 6-to-12 inches of snow Wednesday. However, the southeastern half got 3-to-5 inches, which generated quite a few nastygrams directed at meteorologists. So let’s take a deep dive into what happened.

Related: View here: Snow totals in SE Michigan on Feb. 2-3, 2022

Why some didn’t get as much snow

First of all, I was very consistent in my messaging earlier in the week through my articles here on ClickOnDetroit.com. There were two main themes in my articles:

• This would be a two-part storm, with a Wednesday and Thursday component.
• While I had greater confidence in the Wednesday part, I had great uncertainty in the Thursday half of this.

In my Tuesday article…the day before the storm…I wrote that I expected a potential 6-to-10 inches of snow on Wednesday, but was very uncertain about just how much of the Thursday part would get us. Remember that those forecasts you heard or read from everybody around town (many of which gave highest potential amounts of 10-to-16 inches) were giving you TOTAL snow amounts for the two days. I was trying to provide a bit more detail, and also be honest about my uncertainty.

Rain to snow change was later

Alright, let’s now discuss the meteorological set-up. As you may recall, Tuesday was very mild, temperatures reached the upper 40s in many areas. But at the same time that a cold front was approaching with much colder air, moisture was streaming northward right at us. Rain moved in late Tuesday, as expected, and continued into the night.

Meanwhile, as the cold front moved through, temperatures started dropping and the rain started changing to snow from northwest to southeast. All of the high-resolution computer models Tuesday suggested that the transition to all snow would be complete by 7:00 a.m. or so. But that little detail ended up being wrong as the cold air intrusion slowed down, which made a huge difference in how much snow you got.

Take a look at this snapshot from Storm Tracker 4 from 7:30 a.m. Wednesday.

As you can see, the rain-snow line was only halfway across the area at that time. So it continued raining across the southeastern half of the area much longer than expected and, even when it finally changed to snow, temperatures still above freezing for a few hours melted the snow as it fell.

Bucket half full

It is important to remember that, when a big storm system approaches, there is a certain amount of water vapor available in the atmosphere for that system to turn into precipitation (we call that data precipitable water).

Think of the atmosphere as a bucket: it has a constant amount of water in it to turn into rain or snow. So, when the changeover from rain to snow was delayed, more of the water in that bucket fell as rain, which left less water available to then fall as snow.

The result is that those in the northwestern half of the area, where the snow began as expected, received 6-to-12 inches of snow on Wednesday, while those farther southeast got to 3-to-5 inches.

And, of course, some of you got some additional accumulation on Thursday. Metro Airport, for example finished Thursday with an 8.5-inch storm total, while Temperance in Monroe County ended up with 7.5 inches.

No, it’s not the 12 inches some of you thought you were going to get, but it’s still significant snow. Which brings up one more point: over my long career here at Local 4, one thing I’ve noticed is that, when a range is given in a snowfall forecast (for example, my 6-to-10-inch forecast for Wednesday), many people only remember the higher number of the range.

Meteorologists cannot give a single number in the forecast for a snow amount, there are simply too many variables that can create locally higher or lower amounts, e.g., lake effect and higher terrain such as the Irish Hills.

Let’s say, instead of only remembering the 10-inch number in the forecast, you only remembered the 6-inch number. In retrospect, many more of you wouldn’t have been as disappointed in the how the forecast panned out. So I urge you to always consider the RANGE we give you for an expected snowfall, and not just a single number.

I hope this helps you understand what happened this week. I take great pride in my forecasts…I probably spend more time each day working on my forecast than most TV meteorologists in the country. Half of the area got the Wednesday snow I expected, and half did not. I can only remember one other big winter storm in my thirty-nine years here in which my forecast was more off than this, and that was due to some critical data not available to be ingested into the computer models, which caused a big problem that none of us meteorologists knew about until after the fact.

I remember that my forecast was actually the lowest amount of any meteorologist in the city for that storm, and I was still way off (we got only half of what I expected). Fortunately, this rarely happens but, when it does, it bothers me greatly. But at least in this case, half the area got what I expected on Wednesday.

Now that you have this understanding, channel your inner kid and get out and have some fun in the snow!