Winter Weather Preparedness: Understanding Timeline for Forecasting Winter Storms

 Snow may not be in our forecast just yet, but this week is Winter Weather Preparedness week in Illinois. It's a time to not only look over your winter weather preparedness plans but also learn about different winter weather hazards that can occur and how meteorologists forecast those hazards.

Part of being prepared for winter weather is understanding the terminology that is used when winter weather threatens. Meteorologist Owen Szarley talked about that in an earlier post.

But let's talk about the science of forecasting those winter storms and why you should always be aware of any snowfall forecasts that begin to circulate, especially on social media, several days in advance. It's important to understand that the forecast can, and will, change in the days leading up to a winter storm. This is because often times those upper-level features that eventually lead to larger low-pressure systems are forming over data sparse areas. And until the atmosphere is able to be better sampled, the possible outcomes for developing low-pressure systems can be quite large. But as the atmosphere becomes better sampled meteorologists are able to get a better understanding of how those low-pressure systems will eventually develop and travel, and the impacts they will have on a region.

5-7 days out: Pattern recognition: Meteorologists begin to have a general idea of the region that could be impacted by a winter storm, usually within a 1-2 day window. Any sort of snowfall forecast is still way too early.

3-4 days out: Possible outcomes/scenarios: Meteorologists are able to identify a region, usually within a couple states, that will see impacts of an incoming winter storm within a 12-24 hour window. Exact snowfall amounts are still too early to determine but we can start to give some very broad estimates.

1-2 days out: Figuring out details: Meteorologists now are starting to get a handle of where exactly the storm will travel and start to give general impacts within a 6-12 hour window. General ranges of snowfall totals are discussed.

12-24 hours out: Meteorologists now can give a best estimate of snowfall totals within the county level, usually within a few hour window.

Adjustments to winter forecasts will always happen, even in the hours leading up to - and often times during - a winter storm. But knowing generally what to expect leading up to the storm can help you better prepare for any potential impacting snow or ice that may occur.