The weather in western Massachusetts varied greatly from the valley to the hills. We had another situation today where it was snowing a lot of the time in the Berkshires and the hills west of the Connecticut River, but we barely got any up and down the Pioneer Valley.
This type of system or pattern is called orographic lifting or upsloping. The air or wind hits the hills and is forced to rise as it hits the mountainous terrain. As that air rises it cools and condenses and leads to the formation of snow. That snow just continues to fall over the hilly areas. As it gets to the other side of those hills the air then starts to sink as it heads for the valley.
That sinking air warms and as it warms it dries, so it almost completely prevents snow in the Berkshires from getting into the Pioneer Valley.
We had this situation a couple of months ago, again today and we may get it again before winter is done.