Snow Forecasting Challenge
Predicting winter weather is one of the most challenging aspects of meteorology, especially in our region of the country. No snow is in the forecast, but the rain this Friday morning offers a fantastic opportunity to prove my point.
15:1, 10:1, 8:1, 6:1 ... These are called snow ratios. Let me translate.
15:1 - For every 15 inches of snow, it is the equivalent to 1'' of water
10:1- For every 10 inches of snow, it is the equivalent to 1'' of water
8:1 - For every 8 inches of snow, it is the equivalent to 1'' of water
6:1 - For every 6 inches of snow, it is the equivalent to 1'' of water
What determines these ratios? TEMPERATURE! The colder the air, the higher the ratio. The closer the air temperature is to freezing, the lower the ratio. Have you ever noticed heavy wet snow with temperatures around 32°? It's full of water and easy to make snowballs. These events have ratios around 6:1 and 8:1.
What about snow with temperatures in the teens. It doesn't happen often around here, but it's fluffy with less water content. It adds up faster and is very difficult to build a snowman or have a snowball fight. There's less water and the snow ratio is much higher. Across some of the higher latitudes ratios can exceed 25:1. We typically see ratios around 6:1 to 10:1 in our region.
If we forecast 1'' of rain and we only receive .5'' of rain, no one really notices that or calls the forecast a bust. But when you convert that to snow, it's visual!
Let's use the ratio of 10:1. If we forecast 1'' of water, that means we receive 10'' of snow. What if moisture is more scarce due to unforeseen factors and we only receive .5'' of water which would mean 5'' of snow? That's a visual difference and we hear about it. LOL. That's why we give ranges. 5-10'' of snow in the forecast. Many will hear that and immediately expect 10'' in their yard.
Now look at the doppler radar rain estimates for rainfall as of early Friday morning.
Try making a snow forecast based on this! With a 10:1 ratio, Pine Bluff receives 17 inches of snow and Benton NOTHING. West Little Rock receives 2'' of snow and Maumelle NOTHING. Arkansas county has a solid area of 4'' of snow, but look at the gray area just south of Stuttgart. That narrow area picks up a dusting.
In summary, once we get deeper into winter and forecast snow, remember these challenges we face and recognize the range in your area. One other factor I have not mentioned is sleet. That will always reduce snow totals, but that's another discussion for another day.
I love these challenges and look forward to them. Thanks again for coming to the Arkansas Weather Blog.