Why early snow forecasts are unreliable

As we inch closer to Christmas, many of us might be thinking of snow especially with recent stories mentioning the exact date of when it will fall in your area. But here is why you shouldn't believe all that you read.

Snow is actually very hard to forecast and the bottom line of a snow forecast is that you should never believe one that is for more than three days ahead of time. Even then, forecasts for one day ahead can be incorrect. Let us explain why.

The temperature of the air is perhaps the most crucial aspect when looking at a snow forecast. Generally, when temperatures are below 35 F, snow is possible. In addition, with temperatures less than 32 F, they bring the chance for more dry and powdery snow.

While this sounds simple, whether the snow actually hits the ground as snow depends on the temperature of the air it's falling through. If the air temperature is low enough throughout the air column, the snowflakes that do fall will likely stay as snow.

However, if the snow travels through a warmer patch of air, it will melt and turn into rain or sleet. So while the air on the ground might be cold enough, temperatures further up could be warmer, preventing snow from hitting the ground.

Altitude is another important aspect. For every 328 feet in altitude, temperatures fall by 1.8 F. This mostly explains why mountaintops or hills see more snow compared to the valleys below.

Thirdly, location is important. If you live in a city or on the coast, it’s likely to be warmer than the surrounding area, so the snow could be just a few miles up the road.

Finally, it isn't just temperature, altitude or location that influences whether it will snow or not but wind is also a factor. A sudden change in wind direction can mean you will see either heavy snow or rain depending on where the wind is coming from. Cooler northerly winds can bring a better chance for snow than warmer southerly winds.

So, will it be a white Christmas? You'll have to wait an see! You can see snow in the forecast using our WeatherRadar. We show snow using the color pink and the heaviest snow can be found wherever the pink color is darker.