Whenever snow appears in the forecast, I’m filled with dread. There are two reasons: 1) I hate shoveling the driveway and 2) people ask me “how much snow are we going to get?” I consider myself a pretty decent severe weather forecaster. It’s my particular area of interest, and I’ve given myself some practice at it. Winter weather forecasting is a whole ‘nother beast.
It’s not just that I don’t like it, or that I haven’t practiced (both are true), but winter weather forecasting is really more challenging. There are a variety of reasons — some scientific, some psychological. The most obvious scientific reason is that temperature matters. A three degree difference doesn’t mean much when the temperature is 80 degrees; the rain will still be rain. When the temperature is in the lower 30s, a three degree difference can be the difference between rain, snow, or some awful mix. Surface temperatures aren’t the only ones that matter; small differences in the low-level air temperatures can have an impact on the precipitation type.
Even when you nail the precipitation type, how much snow do you get? A common rule of thumb is that one inch of rain is equal to 10 inches of snow, but that’s a really awful rule. The snow-to-liquid ratio can vary widely. I’ve measured from 2.7:1 to 30:1 at my house, with the average somewhere around 14:1. With half an inch of liquid, the difference between the rule of thumb and my observed average is 2″ of snow.
Then there’s the psychological aspect. For the most part, people don’t care how much rain falls in a given event. Sure, ridiculous torrents like southern Indiana saw last weekend are noticeable, but how many people can look outside and tell the difference between .25″ and .5″of rain? I bet they can tell the difference between 3″ and 7″ of snow, though. Snow also requires more preparation than rain does. You generally don’t see grocery store bread and milk shelves scoured clean before a rain storm. The highway department doesn’t put in overtime to salt the streets before it rains. Schools very rarely delay or cancel classes because of rain.
Snow draws attention to itself. It’s the biggest prima donna of the non-destructive weather phenomena. The natural result is that people become very sensitive to how well a forecast verifies. Unfortunately, it verifies “not good” all too often. I suppose this is my way of saying “is it spring yet?”