The forecast for blizzard-like snow had Minnesotans preparing to hunker down.
Between 6 and 12 inches for the metro, Mankato and Duluth from Thursday into Friday; probably 12-15 for those along the central portion of the Minnesota-Wisconsin border.
Now things have shifted a bit, and a band northeast of the metro into Wisconsin could be hardest hit – while the Twin Cities may "escape" (we use that term relatively) with anywhere from 3 to 10 inches.
Ten inches is still a lot. WCCO says the last time an April storm dropped more than 10 inches in the Twin Cities was 1983 – the cities got 13.6 inches. But the chances of beating that number seem to have dropped a little bit.
By Thursday morning, many local weather reports had changed based on fresher data.
Why the disparities compared to Wednesday? Because predicting weather is really hard and will never be an exact science, says author and statistician Nate Silver.
Silver, author of "The Signal and the Noise: Why So Many Predictions Fail – But Some Don't" and founder of FiveThirtyEight, had an excerpt of his book printed in the New York Times, entitled "The Weatherman Is Not a Moron."
There are a couple properties weather has that makes it particularly difficult, Silver says: First off, weather is "exponential," he says.
"Imagine that we’re supposed to be taking the sum of 5 and 5, but we keyed in the second number as 6 by mistake. That will give us an answer of 11 instead of 10. We’ll be wrong, but not by much; addition, as a linear operation, is pretty forgiving. Exponential operations, however, extract a lot more punishment when there are inaccuracies in our data. If instead of taking 55 — which should be 3,125 — we instead take 56, we wind up with an answer of 15,625."
In addition, weather is dynamic, Silver explains. What weather will do in one instance is based on what it did the moment before.
Those problems helped lead to the projections we have now, which use percentages and model-based predictions coupled with some human judgment. It leads to more uncertainty (a frustration for those of us depending on weather forecasts), but less instances of being flat-out wrong, Silver writes.
That said, Friday's rush hour could still be bad.
FOX 9 says the snow will come in a few shifts: An inch or so of wintry mix Thursday evening in the Twin Cities, followed by 4-6 inches of snow overnight. Friday morning into the afternoon will add another 1-3 inches.
The National Weather Service says wind speed tonight will be in the 15-25 mph range, with gusts reaching 40 mph – potentially reducing visibility. There's a winter storm in effect for most of Minnesota, with "widespread" snow totals of 6-8 inches. The Lake Superior area will likely get the most snowfall, more than 10 inches; the northwest corner of the state the least. In the Twin Cities snow could fall at a rate of 1-2 inches per hour, with thundersnow being a possibility.
Weather.com says Friday's a.m. and p.m. commute will likely be impacted the most.