Snow this weekend: Why did the snow icon on my weather app move

Don Schwenneker Image
Tuesday, January 8, 2019
Why did the snow icon on my weather app move
Hey, Big Weather? Why did the snow icon move on my weather app?

RALEIGH (WTVD) -- Okay, a ton of you are thinking it. "Yesterday, my phone was showing a snowflake on Saturday. Now it's gone. What's going on?"

It's a question our meteorologists get all of the time. So, what happened?

The simple answer is, the models have changed, and they'll change again.

Let's look at one of those weather models: the European (EURO).

Here's what it looked like Monday morning for one specific time period, Sunday morning at 1 a.m.

Looking at the colors, rain is green, wintry mix is pink, and snow is blue.

After showing a snow chance for Raleigh all day on Sunday, it switched that possibility to rain moving the snow line well to the north on Monday. Just 12 hours later, the same model changed.

For the same time period, it moves the rain, sleet, and snow line back to the south and puts a snow possibility in the Raleigh area, again. And that is what your phone is reading.

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Most phone apps don't have interaction with a human. They just take the latest model run and output the data.

And they typically only use one model. It may be the EURO or the American or the Canadian or the weather app's own model.

And every six to 12 hours it gets a new one, changes the phone forecast, and the snowflake disappears.

This is where a meteorologist can make the difference in an accurate forecast.

"To be fair, the models have gotten much better over my 20 plus years of forecasting, but a model does not a forecast make," Big Weather said. "We also like to look at the atmosphere, the data from surface, the Jet Stream, and data collected from weather balloon flights, and we combine it all to make the forecast you see. The other element added to forecast, experience. When we've seen things before, it can change how a certain situation is forecasted."

That experience and other data allow this timeline to take place:

Wednesday we would move into the "Looks More Likely" category from the "It's Possible."

So, what's the weekend going to look like?

It looks wet as we go through the day on Saturday, a wintry mix is "possible" Saturday night, and, with temps in the 40s on Sunday, any frozen precipitation will melt away.