Forecasting winter weather a slippery task
Anytime there's a mention of snow in the weather forecast, lots of Tri-Staters ask what seems like a simple question: "How much snow are we going to get?"
Forecasting winter weather a slippery task Anytime there's a mention of snow in the weather forecast, lots of Tri-Staters ask what seems like a simple question: "How much snow are we going to get?" Check out this story on thegleaner.com: https://www.courierpress.com/story/weather/2016/12/09/forecasting-winter-weather-slippery-task/95174996/
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Jeffrey Walker, Evansville Courier & Press Published 3:24 p.m. CT Dec. 9, 2016 | Updated 8:02 p.m. CT Jan. 11, 2019
Severe weather and snow can prove treacherous for drivers during the winter months. Check out this animation with some do's and don'ts for drivers venturing out in #winterstorm 2015. USA Today
A recently-produced graphic from the National Weather Service in Kansas City illustrates the difficulty of winter forecasting.(Photo: Courtesy of NWS Kansas City)
Predicting the answer, it turns out, is anything but simple.
WTVW/WEHT Chief Meteorologist Wayne Hart and SouthernIndianaWeather.com's Michael Wilhite were asked to shed some light on winter forecasting.
More: Winter storm warning goes into effect in Evansville tonight at 6 p.m.
More: How to prepare for snow in Evansville, Henderson
As both pointed out, there are many factors to determining long-range (in this case, think between seven and 10 days) forecasts in the winter.
First, there are "the computer models." Long-term models tend to have lower "resolution" – simply put, they don't show as much detail as short -term models, and therefore are more open to interpretation and have more room for error.
"A lot of times," Wilhite said, "models don't see the little details that would allow us to predict the correct solution."
Hart added: "The models do a pretty good job of telling us that we'll have a big storm a week out, but a relatively small shift, say 50 miles or so, can be the difference between a cold rain and a heavy snow."
"A lot of it has to do with where we are geographically. We are, in most cases, right around the rain/snow line, and that causes us to have a wide range of amounts across the area." Hart said. "Even a day out, it's sometimes hard to say not only when precipitation will change from rain to snow, but then also when it will start to stick."
Further, Hart says, "Models struggle with arctic air masses. They want to move them out faster than the air will actually move."
Both pointed out that a small miss in a winter forecast is more obvious than a similar miss in warmer weather.
"We typically use a 10-to-1 ratio for rain to snow," Wilhite said. "Every tenth of an inch of rain is an inch of snow."
"You tell people they're going to get two inches of rain and they only get an inch, and they probably won't be too upset," Wilhite said. "But that could be a huge difference in snowfall."
And after figuring all that, there are climate markers to consider. Is an El Nino or La Nina active?
"Those will ramp up the jet stream and lead to more weather extremes," Wilhite said.
And don't even mention a "polar vortex."
More: Here's where you said not to drive in snow, ice around Evansville
Hart's been the chief meteorologist at WEHT and WTWV since 1993, so he's seen a lot of Southern Indiana winters. But, he says, technology is, in some ways, making his job harder.
"Nowadays, anybody can put a nice graphic together and make you think we're going to get a bunch of snow. But who knows if they know anything about weather? It could just be some high school kid in Iowa having a little fun, and the next thing you know, everyone is sharing his graphic."
"You get clicks by putting out something dramatic" Hart cautioned. "There are a lot of local meteorologists you can trust, and the National Weather Service, too. Before you share, look at the source and make sure it's something you can count on."
The City of Evansville filled twelve salt trucks in preparation for an incoming winter storm, Friday, January 11, 2019. Sam Owens, Courier & Press
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