Understanding Why Snowfall Forecasting is a Tricky Science

The first widespread snowfall of the year is on the horizon for the northern U.S. Snow can be a tricky thing to forecast for several reasons. Here are a few things to keep in mind the next time that snow is bearing down on your region.

Difficulty of Predicting Snow Far Out

Even with today's modern forecasting tools, it can be difficult to predict snow more than a few days out. A lot can change in the forecast as a snow event approaches a region, making it hard for meteorologists to pinpoint precise snowfall amounts. A minuscule change in the amount of moisture can mean the difference between an inch of snow or a blizzard.

While forecasts may signal the potential of a snowstorm a week out, it is important to keep in mind that a lot can happen in the days leading up to the event. Do not alter plans just because snow is in the forecast that far in advance. Instead, keep monitoring the forecast with the knowledge that it may change significantly.

The first time that you hear of the hint of snow is not likely to be the last. Forecasts are updated several times per day, each time with more precise information. Each model run provides a clearer picture of what will really transpire, particularly when you get within a day or two of when the flakes are expected to begin to fly.

Snow is Highly Localized

Snowfall accumulations are highly localized. Just a dozen miles can make a meaningful difference in snow totals. This is even more apparent when dealing with areas at different elevations. As such, it is important to seek out hyperlocal forecasts when determining what to expect for snow.

For example, larger snow zones often come with smaller bands of heavier snow within the impact area. Because these bands may only be a few miles in width, it is easy to see how some areas may get hammered with snow while other communities escape significant accumulation.

It is common for there to be a sharp gradient in snowfall accumulations on the northern edge of a system, as this is where the dry air tends to infiltrate. The line of delineation between the heavy and light snowfall totals is typically where the drier air stops advancing. Because it can be so difficult to predict the advancement of dry air intruding into a storm, it is also difficult to forecast snowfall accumulations within this zone. It is also not unusual for the National Weather Service (NWS) to issue a winter storm warning to keep people alert on the chance that they end up in the primary impact zone for heavy snowfall.