Why more wintry mixes and less pure snowstorms this winter?

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CHICOPEE, Mass. (WWLP) – We are almost halfway through February and we still haven’t had much snow this month, at least in the lower Pioneer Valley.

At Westover A.R.B. in Chicopee, so far we’ve only measured half an inch of snow since February began, but we should have had 5.3″ so far this month.

Since October the lower Pioneer Valley has had just under 27″ of snow, but we should have had a little more than 31″ so while we are a little below average, that big December storm means we’re not far off.

Yet for the past couple months we’ve had very little accumulating snow. Why? Because we’ve been so mild.

To explain this we look at the jet stream, which is an area of strong winds high in the sky. The farther south the jet stream is the more cold drops south from Canada. So far the jet stream much of winter has been fairly straight. A straighter jet stream locks most of the cold air north of us and we get fewer pure snowstorms and instead more wintry mixes.

We would need more of a wavy looking jet stream if we were to have more cold. In a wavy jet stream more cold comes in where the jet stream dips and that gives us better chances for pure snowstorms if a storm system is nearby during one of those colder periods.

The Arctic Oscillation (AO) is one of the climatological indicators that help measure pressure levels over the arctic. The lower the pressure over the arctic, the straighter, faster and farther north the jet stream usually is (positive phase). The higher the pressure over the arctic, the wavier and farther south the jet stream usually is (negative phase).

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