Here’s What You Need To Know About Snow Forecast Maps You May See Posted On Social Media | The Weather Channel – Articles de The Weather Channel


  • Winter storm forecasts can be uncertain even a day or two in advance.
  • Maps showing long term snow forecasts from individual computer models should be ignored.

Major winter storms affect the United States every year and bring with them major disruptions in daily life.

In order to understand how important a disturbance can be, the most pressing question is always: how much snow will I see?

The eagerness to know what impact a snowstorm or ice storm will have is understandable, but unfortunately there are times when that question is not answered for one to three days after it arrives.

This thirst to know what’s going to happen can often be fueled by computer model predictions of snowfall amounts that often go viral on social media. Sometimes you can see these cards with pretty blue, pink, and purple outlines until about a week before a storm hits.

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Example of a forecast of a snow model with different colors representing the amounts of snow.

There is nothing to be done about these cards; they will never disappear from social networks. But you can do your part by not buying what they show and spreading them like a nasty cold bug, either.

Here’s a weather rundown that explains why you should avoid sharing long-range snowfall forecast maps.

Meteorology Behind Snow Forecast Maps

Weather models often show meteorologists that there is a potential for a major winter storm five to seven days in advance.

For example, there could be indications in the forecast model forecast on a Monday morning that a winter storm could affect several areas of the United States the following weekend. But instead of showing specific details, meteorologists usually just announce that we are monitoring a particular storm within a general time frame. This is usually followed by the caveat that the forecast will change and we will provide more details as they become available.

Part of the reason for this caveat and lack of detail is that the weather disturbances triggering the development of a potential winter storm could be thousands of miles from their future destination. This means they can travel to a more data-less region, such as the Pacific Ocean, before reaching the United States.

Without robust data, numerical forecast models can have difficulty solving important details about how a winter storm can form from this or these incipient disturbance (s). It is a basic concept of forecasting models that initial analysis errors or short-term forecasts increase over time.

Ask questions about the location and depth of the cold air source, and there are countless uncertain scenarios forecasters face when facing a winter storm in a long range forecast.

All of these uncertainties lead to the about-face often seen in long-term snowfall forecasts from computer models.

For example, you might see a map posted on social media that shows 6 or more inches of snowfall (Run Model # 1 below) for your city from a storm that’s still five or more days away. That same model might change its tone and expect an inch or two of slush in its next update 6 to 12 hours later (Model Run # 2 below).

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Example of changes in back-to-back model snowfall forecast made six hours apart for a potential storm in 5-7 days.

In addition to this, these maps often do not take into account how much snow can be produced from the predicted amount of liquid equivalent precipitation, also known as the snow ratio. Snow totals on maps may also be inflated in areas where slush is expected rather than snow.

So the next time there is a potential for a significant winter storm in your area, resist the temptation to post the forecast on any snow map you might come across on social media.

Instead, consider the source. If the person who posted the image isn’t a familiar face you saw on TV, or a qualified meteorologist from the National Weather Service or a private forecasting company like weather.com, a quick search on Google by its name will almost always tell you in less than 30 seconds if it is a reliable source. Skilled meteorologists shouldn’t share crazy forecasts for a week into the future. So if you can’t find the person’s portfolio and credentials in a web search, take what they post with several inches of skepticism.

The Weather Company’s primary journalistic mission is to report on the latest weather news, the environment and the importance of science in our lives. This story does not necessarily represent the position of our parent company, IBM.


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