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November 6, 2019

First Snow of the Season Set for Thursday in Ithaca

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Ithaca is set to receive its first snowfall this Thursday, marking one of the first milestones in Ithaca’s notorious winter. So, what can Ithaca expect from this upcoming season?

As it stands, the campus can expect around 4 inches of snow on Thursday. Don’t reach for your winter boots and shovels just yet, as these predictions do not just measure the amount of snow that will accumulate on the ground.

“There’s about a 60 percent chance that we will have above normal temperature … By the same technique we are predicted above normal precipitation.  Now that’s not necessarily snow, that’s liquid water,” said Prof. Stephen Colucci, earth and atmospheric sciences.

“The models predict liquid equivalent, or melted, precipitation,” Colucci said. “Usually 10 inches of snow melts to one inch of liquid water, but this can vary;  lake-effect snow can be very dry while storms tapping water from the Atlantic Ocean can be very wet.”

Snow forms when temperatures drop and water vapor in the atmosphere becomes solid, skipping the liquid phase. This process requires both moisture and the rising of air, which results in the air cooling.

Differences in the conditions that create snow manifest in different types of snow, often called “dry” or “wet” snow.

“Dry snow is easier to shovel, it’s light and fluffy. Wet snow is very heavy and dense, which makes it more difficult to shovel,” Colucci said. The snow that eventually finds its way onto campus typically originates over the Great Lakes; this “lake-effect snow” is often relatively dry.

Should there be snowfall on Thursday, it would be nearly two weeks earlier than the average first snowfall in Ithaca, November 20th.  The first traces of snow were cited on October 18th last year. What does this mean for the rest of the winter, and is Ithaca on track for another polar vortex?

As of now, it’s difficult to say.

“[Forecast models] are computer models that describe how today’s weather will evolve into tomorrow’s weather,” Colucci said. “These models can run up to 16 days in advance, but the public never hears that because the models, after about seven days, become wrong.”

According to Colucci, forecast models rely on atmospheric measurements that are only taken in select locations, like the Ithaca and Syracuse airports, which leads to errors in the models. “There’s errors, first of all, in the data you’re feeding the weather models. There are also errors in the way the models are calculating what’s going to happen,” Colucci said.

While weather model accuracy falls apart after about a week, meteorologists have made predictions regarding the nature of the coming winter.

Predictions made by the National Oceanic and Atmospheric Administration anticipate higher than average temperatures and precipitation.  These predictions cite patterns over the Pacific Ocean in addition to weather trends from previous years with similar atmospheric conditions.
Utilizing atmospheric temperature data and predicted precipitation data from NOAA, Colucci estimated: “If this forecast is right we can expect 4.3 inches of snow. Whether or not that’s right, we will have to see.”