At the first hint of snow in a forecast – or rather, when a computer module hints that there could be a snowstorm developing – it could be more than five days away. And even though a computer forecast may be dumping a foot of snow on Philadelphia seven days out, there’s no way that we, as TV meteorologists, would predict a foot of snow a week in advance.
If the storm is continually predicted to be the same strength and stays on the original track, the snow forecast then becomes a bit more certain, especially if it’s three to five days out. By that time – in this case, Wednesday or Thursday -- we can start to look at probability forecasts for heavy snow. For instance, there is a high chance for significant to moderate snow in a certain area while other regions may only have a low chance for significant snow.
As you get within one to three days of a forecasted snowstorm, there is a better picture of the track, strength and timing of the storm. A number of higher resolution computer forecasts only go out 48 to 84 hours, so this is where you get a good idea of the amount of snow that is expected. 36 hours prior to the start of a snowstorm, you are likely to see an actual snowfall accumulation map and storm timetable.
This weekend’s potential storm more than two days away and we are still looking at new information that comes in every six hours. That means there is always new computer forecasts to analyze and act as guidance in making a snowstorm forecast.
It looks like the storm track has shifted a bit which will impact the snowfall potential.
Keep up with everything snow as we continue to cover the potential storm. Each couple hours, we’ll be able to be more concise when it comes to snowfall totals and timing as newer data comes into the Weather Center.