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WEATHER LAB | The challenges of long-range weather forecasting

The farther away a forecast is, the more difficult it is to predict with any certainty.

DES MOINES, Iowa — As winter approaches, it's important to exercise caution when accessing weather forecast information on social media, blogs, or via other online media.

In fact, it's best to only look at forecast information from a reliable source of weather, like Local 5's team of meteorologists, for instance. 

It's the season where social media posts make big claims about upcoming winter storms or cold snaps, even when the actual event is a week or two away. 

Sometimes, it's not even a guarantee a particular storm system or weather event will develop at all.

Weather forecast models take current weather conditions and analyze them using a set of complex mathematical equations to predict what the future will be like.

In the long-range, such as 10 days or even two weeks out, forecast models can put out a variety of different scenarios with countless combinations and possibilities. 

At any given time, weather models only show one solution, which may or may not eventually come true.

As the period of interest gets closer, such as in the 3-5 day range, the forecast becomes a little clearer since there are fewer possibilities available in this timeframe. 

Still, in this range it is often difficult to offer specifics in the forecast. It may be obvious a system is going to develop, but determining exactly what time it arrives or what specific impacts may occur is tricky.

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The greatest clarity arrives when a forecast is one or two days out

Weather forecast models are usually in decent agreement at this point about what solution is most plausible given the most recent set of current conditions.

When you stumble across posts referring to "deadly cold" or "historic snow" in a few weeks, take a pause and think about whether or not this makes sense.

Given the current limitations of weather forecast models and general knowledge of the atmosphere, it is impossible to predict something accurately that far away. 

In the long-range, computer models often showcase unrealistic weather scenarios that more often than not fail to materialize.

If a storm system warrants big headlines and requires greater emphasis on the expected impacts, you can trust Local 5's team of meteorologists to inform you in a calm, yet dependable way. 

Download the We Are Iowa app or subscribe to Local 5's "5 Things to Know" email newsletter to get the latest weather forecast.

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