FORT WAYNE, Ind. (WANE) – With Indiana’s Winter Weather Preparedness Week underway, it is important to remember the limitations of long-range snowfall forecasting.
You have likely seen a snow forecast far in advance like this one that was posted on Sunday. It looks very scientific and precise, with snowfall predicted down to a tenth of an inch for this upcoming weekend.
The reality is this data should not be trusted. Meteorologist Nathan Marsili with the National Weather Service in Northern Indiana says weather forecast models can vary considerably from day to day. The data becomes less reliable past around four to six days in advance or sooner.
It is important to understand weather forecast models are based on initial conditions. Models have trouble deciding on how weather systems will evolve if the system has not yet developed or is located over the ocean at the time of the forecast. For a system tracking toward our area, the forecast models need the system to make landfall on the west coast. The system then becomes easier to project into the future because of ground observations and upper-air balloon launches conducted by the weather service. Not very many observation points are available on the Pacific Ocean; satellite and aircraft observations are also available, but still do not capture the entire behavior of a weather system.
Marsili says the network of upper-air observations does not cover the entire United States and is not perfect. Therefore, weather forecast models can still change quickly. It is important to gather information from a variety of forecast models, as small scale factors play a role and one model is not always the best.
This is why the role of your local meteorologist is crucial. We can interpret this data from a variety of sources and equip you with a trusted forecast. The weather service uses a funnel approach when it comes to snow forecasting. They start with a broad approach as soon as they feel snow is possible, then narrow down the impacts three to five days out and issue forecasted numbers roughly one to three days in advance. Not every weather system is the same, but this is the general pattern the weather service follows.
Ultimately, if you see a weather model snowfall forecast posted and the time period is still several days away, do not trust it and report the person. This is becoming more of a problem as model data becomes more accessible and more people are figuring out the websites where this data is posted. Do not fall for clickbait and wish-casting.