Ask any meteorologist in the Triangle, and he or she will tell you that winter storms are the hardest thing to forecast here. Believe me. It's true. So, why is our winter weather so hard to predict?
When the difference between rain and freezing rain comes down to a degree, things get complicated. In the case of Tuesday night's Winter Weather Advisory, the computer forecast models had a good handle on how low the temperature would go, but the timing of the cooler air's arrival and the amount of precipitation were the variables that made the difference.
The GFS model had the temperature dropping to below 32º around 7 p.m. Tuesday evening. Most forecasters bought into that timing, which is why the advisory started at that time. Some of the models showed much more precipitation than we actually received. The expectations were anywhere from a trace and a quarter of an inch.
A quarter of an inch would have been bad all over. Instead, our official reading at the airport was 0.02 inches, which was just enough to cause patchy ice on bridges, overpasses, other raised surfaces, and things like porch steps. If you ask one of the drivers involved in the auto accidents caused by ice, they would probably tell you it was bad enough.
With a range from almost nothing to something worth worrying about, most meteorologists will err on the side of caution when wording their personal forecasts and choose to say "up to a quarter of an inch" because we know that the majority of people listening to or reading a forecast will only remember part of what they read. We want you to remember whatever will put you in the safest position. As a meteorologist, it is my job to make sure that I provide the information that you know in order to protect yourself, your loved ones and your property. All meteorologists take that responsibility very seriously.
Imagine if forecasters predicted just a trace of ice at most, but a quarter of an inch coated everything in sight when we woke Wednesday morning. How much would your plans have changed and how upset might you have been if you weren't prepared for the worst case scenario? The Department of Transportation likely would have treated the roads differently, too. The forecast, especially a winter weather forecast, makes a difference in so many ways. When it comes to the weather and public safety, it is always better to be safe than sorry.