GRAND RAPIDS, Mich. (WOOD) — It’s a question we get a lot, “How much snow would we have seen if all this rain had fallen as snow?” It usually happens when we are in a particularly mild stretch, or have just been dumped on by a whole bunch of cold-season rain.
The answer to this question isn’t as easy as you might think. Much of meteorology and forecast outcomes are dependent on a wide range of variables.
So, even though one inch of water usually gives us 13 inches of snow in the United States, according to the National Severe Storms Laboratory, we can’t just do a simple math equation. Even though the “average” snow to rain ratio is 1:13, it can and does vary wildly in real life.
An inch of rain can give us only two of heavy, sleety, snow. Or on the extreme end, one inch of water can be transformed into 50″ of dry, fluffy, powdery snow! So, while the 13:1 measurement is the standard baseline, meteorologists often have to look at current conditions to see how incoming moisture will convert to snow.
The other tricky part of this question comes with the fact that cold air masses can’t “hold” as much water as warm air masses.
A warm air mass in January can launch our temperatures up to 50 degrees. It can also dump 2.50″ of rain. A cold air mass can’t physically do that. According to the ideal gas law, a colder air mass is denser. If the temperature drops in the air mass, it won’t be able to pick up or drop off as much water as one coming from the Gulf of Mexico.
So, when we see a huge precipitation event and people ask “how much snow would this be?,” we always have to remember that if it were cold enough for snow, that cold air mass is likely too cold to hold 2.50″ worth of water to begin with.
All this being said, it is still fun to see how much water has fallen this winter season. So far this meteorological winter (December, January, February), Grand Rapids has seen 7.81″ of precipitation. That means all the rain and melted down sleet and snow added up to 7.81″.
If we were to use the standard 13:1 ratio, this would give us a whopping 101″ of snow so far! It’s a fun tidbit to throw around. But if you do! Remember the actual total would likely be much less due to the fact that our big rounds of rain, like the one that happened on Jan. 11 would have been too much water to have dropped as just snow.