Many factors affect snowfall forecasts
Snow — some hate it, some love it.
Regardless of how you feel, the impacts will be felt in mid-Missouri. Whether it be a minor inconvenience or major risks leading to cancellations, it’s important not only to you the viewer, but for meteorologists to understand the challenges of snow forecasting.
Some factors that determine how much winter precipitation we will see include snow-to-liquid ratio, snow banding and dry slots. Any last minute, small change in any of these during a winter storm can dramatically shift how much snow we see on the ground.
The snow-to-liquid ratio compares how many inches of snow melts down to 1 inch of water.
This can make a big difference between the type of snow we see. This ratio is set depending on location, type of system, time of year and atmospheric conditions, including the temperature profile, which is determined ahead of an event. If any of these things change during a winter storm, the ratio changes as well, meaning snowfall totals change.
The lower the ratio, which on average is 10 inches of snow to 1 inch of rain, the wetter the snow. This type of snow is not only harder to shovel, but is typically the best for creating snowmen and at times can cause issues for power lines. The higher the ratio, the lighter and drier the snow. This snow blows around better in the wind and could cause problems on roadways.
In addition, snow banding has major impacts to a snowfall forecast. Snow doesn’t fall at even rates throughout the areal coverage of a storm. Instead, we see banding that produces a higher concentration of snowfall in localized areas. This happens due to tightening pressure and temperature gradients intensifying throughout a snow storm. Much like summer storms can lead to higher amounts in some areas, the same occurs during the winter months.
The last and still important factor is the dry slot, which can completely kill snow chances. This is a common feature of mid-latitude cyclones that typically pulls in cooler and drier air from the northwest, eroding rain and snow chances. The track of the storm can significantly alter the location of a dry slot, which ultimately for any of the factors mentioned can make or break a forecast.
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