So on tonight's newscasts I explained that some valley snow is possible by late in the day on Christmas. I also said that it's still up in the air - that the snow level could be anywhere between the valley floor and 1,000 feet. Why don't I know exactly what's going to happen? Well - that's a pretty complicated question!
Forecasting, in general, is very complicated. One part of most meteorologists' forecasts is advanced computer models. But those computer models often make mistakes. They make mistakes because the data they ingest is often inaccurate. Additionally, the data is typically incomplete. And, the computer models themselves typically don't have the atmosphere modeled completely accurately.
The bottom line - meteorology is more of an art than a science! =)
But creating that art - and having a forecast be accurate - becomes much easier as the day in question gets closer and closer. Take, for example, Christmas Day. Right now - three days away - it's tough to say what's going to happen. It could be snowing in Portland...or it could be raining in Portland...or it could be sleeting in Portland! But as we get closer and closer to Christmas Day, the forecast will become much more focused, and much more reliable. That's the nature of these computer models - and the forecasts we base them on.
So - only time will tell if Santa has some snow in his bag! =) I'll keep you posted!