Metro Detroit snow totals: Why Wednesday's weather forecast was wrong

DETROIT (FOX 2) - When we woke up Thursday to a deeper blanket of snow than expected across Metro Detroit, it raised a fair question: how did this system manage to squeeze out way more than what the forecast suggested? 

VIEW: Southeast Michigan snow totals

The answer comes down to three scientific factors that all lined up just right — or just wrong, depending on how much shoveling you had to do.

Here are the three big reasons we ended up with higher totals:

1. The two frontal systems slowed down dramatically.

We went into this stretch expecting Tuesday’s initial front — the same one that brought those passing rain showers — to scoot east and leave our forecast zone. Instead, it hit the brakes. At the same time, the second, much stronger cold front moving in from the northwest also slowed down. 

When that happens, the atmosphere basically has more time to work with the available moisture. Even more importantly, the slowing of the first boundary allowed moisture to be pulled back into Michigan as the second front approached. That moisture recycling created a longer-lasting system overall. 

The event stretched out several extra hours beyond what models were signaling, and those extra hours of snow really added up on the ground.

2. Winds tapped into Lake Huron and boosted coverage.

We were anticipating some lake-enhanced snow — that’s pretty typical in these northwest flow setups — but the enhancement ended up being much more robust than expected. Winds aligned just right to draw additional moisture off of Lake Huron, and instead of staying confined to the Thumb or drifting east, those bands fanned out over a broader portion of metro Detroit. 

That meant steadier snow for a longer portion of the day, adding yet another bump to totals.

3. The snow-to-liquid ratio was unusually high.

If you picked up yesterday’s snow, you probably noticed how light and fluffy it felt. That’s a clue that the atmosphere was producing snow with a higher-than-normal liquid-to-snow ratio. Around here, the rule of thumb is roughly 10 inches of snow for every inch of liquid. 

Yesterday, the ratio jumped to 15-to-1 — and in some pockets, even higher. When snow is that dry and powdery, it stacks up quickly. It doesn’t take a lot of moisture to create a lot of accumulation.

When you combine a slower system, unexpected lake enhancement, and fluffier-than-normal snow, it becomes clear why the totals nudged higher than what we projected. Forecasting winter systems is always part science and part timing — and in this case, all three ingredients shifted just enough to give us a bigger shovel day across Southeast Michigan.

More snow in the forecast

The snow tapers off Thursday morning, but it won't be the last of it this week.

More snow is expected around the morning commute Friday. This system is expected to drop 1-3 inches on Southeast Michigan, and will likely make for another rough drive.

VIEW: Live road conditions

Snow showers continue Saturday with a couple more inches possible.

If we’re lucky, Sunday offers a brief break before another system arrives Monday.

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