Here’s Why We Wait For Snowfall Totals

A single model run almost never tells the whole story - especially from several days out.
Published: Dec. 10, 2020 at 6:36 PM CST|Updated: Dec. 10, 2020 at 6:37 PM CST
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MADISON, Wis. (WMTV) - Madison and much of southern Wisconsin is expecting snow this weekend. The numbers have been changing constantly and the meteorologists keep saying “we’re monitoring it”. Why?

To give you some perspective, yesterday’s 12Z (Morning) run of the Global Forecast System (GFS) model painted nearly a foot of snow in Madison and more than two feet in Milwaukee. Today, the 12Z model run at the same hour dropped the weekend total to near 4″ in both cities. Talk about a difference a day can make!

A single model run almost never tells us the full story. Instead, meteorologists rely on several models run over several days in order to make snowfall projections. Models run several times per day - each with new information at the start. Consistency between those model runs increases confidence in that particular model’s solution. However, an overall confident forecast also depends on how different models react to the same weather system. If several models handle a weather system in a similar way, confidence increases.

Sometimes the details surrounding a weather event become clear several days out. Sometimes, the fine details become clear 12-24 hours out. In either case, it’s always a good idea to check the forecast before making plans.

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