Actions

How much snow would Friday's rain have been?

Explaining snow ratios: After a rainy day have you ever wondered how much snow would have fallen if it had been cold enough?

By: Katie McGraw

Posted

and last updated

Friday was soggy, with widespread and steady rain throughout most of the day.

When all was said and done, many communities picked up around 0.5-1.00 inches of rain. This includes Cleveland at 0.70 inches. But what if that had been snow instead of rain? How much accumulation would we have picked up?

To explain this, we have to discuss "snow ratios." This is the percentage of water to snow. The old rule of thumb was that for every 10 inches of snow, there would be 1 inch of water (10:1). So, for example, yesterday would have resulted in 7 inches of snow in Cleveland.

That said, many variables can affect the ratio of liquid water to snow, and the rule of thumb, while helpful, is usually not quite right. The snow ratios can even change dramatically within a snow event itself. Snow ratios are tricky to forecast and sometimes can result in significantly more snow (or sometimes less) than predicted.

Some variables that come into play include temperature, moisture and wind speeds. The warmer it is (closer to freezing), the lower the ratio. Snow falling in drier or colder air typically has a higher snow ratio, around 15:1 or 20:1. Deep cold generally promotes higher snow ratios and can pile high quickly.

Using the 20 to 1 ratio, every 1 inch of rain would result in 20 inches of snow. Using the same example as above, 0.70 inches of rain would have resulted in 14 inches of snow had it been much, much colder.

Check out another visual example below using 0.32 inches of water.

Additionally, snow ratios will be lower if there are more super-cooled water droplets in the cloud. If there are more ice crystals, snow ratios will be higher. And if it's windy, snowflakes can fracture, losing their "lacy" structure and leading to lower accumulations (lower snow ratios).