Don't Believe The Hype Just Yet

You might have noticed a specific snow forecast being shared on social media Friday that claims we are going to get half a foot of snow next Tuesday. Before you buy into the hype, let's make one thing clear: This forecast has VERY LITTLE to ZERO credibility. Here's why.

Forecasts are constantly changing because the model data we look at on a daily basis is constantly changing. Especially in the winter, subtle changes in the path of a storm system or the temperatures in the atmosphere can make a huge difference in the kind of weather we actually see on the ground. When a storm system is 3-4 days out, like the one we're expecting next week, the models can change a little every day leading into the actual weather event. Those little changes may not mean much by themselves, but the sum of those changes can completely change what we put in the forecast.

Snow Forecast: GFS - Friday 6z Run

Here's an example. Take a look at what the GFS (Global Forecast System) model gave us for Tuesday snow totals during its late Thursday night run. Not too shabby, right? The bullseye for the heaviest snow is sitting to our north, but areas in northern Illinois stick pick up a good 3-6". Sound familiar to what was going around on social media?

Snow Forecast: GFS - Friday 12z Run

Fast forward 6 hours to the Friday morning run of the GFS, and you'll notice that everything has shifted north. Like, a lot north. In this scenario, we don't see ANY accumulating snow. If you're forecasting solely off the GFS, a 75 mile shift in the path of the storm has completely changed your forecast in a matter of hours.



As meteorologists, there are a few things we look for in the models before we can say with confidence that we're going to see a big snow event. The most important thing is consistency. The models this weekend could swing this storm system back to the south, but if we continue to see a northern track heading into Monday, things are looking good that we won't see a major snow event.

NWS Chicago: Friday's Weather Headline

Here's an example of the right way to warn the public of a potential weather event. We know based on the general path of next week's storm that we are going to see something. But the variables are still changing, so the NWS Chicago office mentions some of the potential scenarios (Snow/Rain/etc.) instead of throwing up some ambiguous snow graphic. They tell you to be prepared, but that's it's too soon to be worried.

In case you're wondering, here's how we like to do things in the First Warn Weather center. We will issue our official snow forecast 24 hours ahead of the actual event to ensure the highest level of accuracy. We will talk about the snow and what it could do a few days ahead of the event, focusing on the factors that could result in a significant snowfall.

In short: DON'T BELIEVE THE HYPE. It's our job to prepare you, not scare you. Anyone who says or does otherwise doesn't understand the purpose and importance of this job. -BA