The calendar says it's spring, but that's not fooling the Swedes or any of us
FARGO — The first time this season that snow fell here and didn't melt right away was in early December, when a blizzard caused many schools to cancel classes or let students out early.
It's been nearly 120 days, a third of a year, and the snow still hasn't gone away.
It might seem like an extra-long winter but, if you ask WDAY Chief Meteorologist John Wheeler, these snowy stretches aren't all that unusual, though the longevity of the winter snowpack is a bit above average.
"This is something that happens on average about one in every five years," he said Monday, "and, interestingly enough, the last time this happened was exactly five years ago."
In 2013, the snowpack didn't all melt away until April 26, he said.
According to North Dakota State Climatologist Adnan Akyuz, the length of the snow season here can vary greatly because we're far from the equator where sunshine is more constant and far from the oceans, which tend to have a moderating influence on weather because they don't change temperatures very quickly.
He agreed that this winter isn't all that unusual.
Technically, it's actually spring right now.
Meteorologists consider December, January and February to be winter months for statistical purposes. These are, on average, the coldest months in the northern hemisphere.
A more traditional way of dividing the seasons is based on the position of the sun relative to the earth. Winter begins with the winter solstice, when the noon sun appears the farthest south from the northern hemisphere. This also makes it the shortest day of the year. Winter ends with spring equinox, when the center of the sun is directly over the equator, with that center moving north in the days that follow.
This year, spring equinox fell on March 20.
"Most meteorologists who have thought about this take issue with the idea of the astronomical first day of spring," Wheeler said. "Spring doesn't magically start everywhere on earth or everywhere on the northern hemisphere on one magic day."
He said when he counts the total snowfall for this winter, he'll count Monday's snowfall, too. "So as far as I'm concerned, this is still winter."
There is at least one other definition of winter. The Swedish Meteorological and Hydrological Institute said true winter is when the average daily temperature remains below freezing for at least five days; even when warmer days follow. Spring arrives when average daily temperatures are between zero and 10 degrees Celsius — or between 32 and 50 degrees Fahrenheit — for at least seven days; even when colder days follow.
By that definition, it's still winter here. It managed to get above freezing just three days in a row in March and it's definitely below freezing now, according to National Weather Service records.
Lots of variability
As most longtime residents know, the weather here can change a lot from day to day, and that makes a difference over the length of a season as well.
According to Akyuz, a key reason is Fargo's distance from the oceans. The main influence on air temperature is not the sun but the sea and the earth, which absorbs the sun's rays and releases the heat over time. Water takes five times as much energy to heat as soil because it's always churning and cold water deeper down will mix with warmer water at the surface. That means the ocean temperatures are slow to change, producing mild coastal climates.
That doesn't happen with soil.
Wheeler said the soil here is very dark, almost black, and when there's no crops covering them, as is the case this time of year, "those fields just suck up that sunlight."
Given that the summer solstice, which falls on June 21 this year, is when the sun is directly overhead and the sun is either marching towards that position or away, the sun exposure at this time of year is about the same as in late August or early September, according to Wheeler. The snowpack, which reflects sunlight back into space, is what prevents the soil from absorbing the heat.
That means as the snowpack melts, it will hasten the arrival of warm weather, which melts yet more snow. But if new snow keeps building on the snowpack, cold temperatures will linger.
The bad news for those yearning for spring is snow is in the forecast later this week and temperatures will remain below freezing throughout each day.
If it's any consolation, Wheeler said it's all perfectly normal. The average snowfall in April here is 3 inches, he said.