Snowfall Reports Are Usually Best Gussses, But They're Still Valuable (And Entertaining)

Snow depth in my yard in St. Albans, Vermont was 10
inches Thursday afternoon. We had about 13 inches of snow
in the past week, but it compacted

When I can, I report to the National Weather Service how much snow fell around my house in St. Albans, Vermont during winter storms, like the one we had Wednesday. A lot of Vermonters do that.   

The NWS office in South Burlington, Vermont, and all other NWS offices for that matter, definitely welcome these reports, as it gives them an idea as to who's getting hit the hardest. It also helps them determine how accurate their pre-storm forecasts were.

That, in turn, helps the meteorologists understand local patterns, and how specific winds, temperatures and other factors influence snowfall. It makes for better forecasts the next time a storm rolls around.

However - and this is my opinion - snowfall totals are probably the least accurate meteorological measurements you can come by, even if these measurements are still useful.

Sure, anything can muck up any kind of measurement. Even things like temperature readings, which you'd think might be pretty straightforward. You look at the thermometer and it indicates it's 30 degrees outdoors. That should be the final word. It's either 30 degrees or it isn't.

Well, maybe it really isn't. If you have the thermometer in the wrong place - maybe it's less or more than the standard five feet off the ground, or it's influenced by sun shining on it, or it's surrounding by asphalt to create an urban heat island effect and suddenly that 30 degrees you saw on the thermometer is pretty unreliable.

As you can imagine, snow is even harder to measure accurately. It blows around. It compacts. It melts and refreezes. Often all within a matter of seconds or minutes.

Which means you shouldn't take snowfall measurements -especially record breaking mega-amounts  - as gospel. These measurements give you a pretty good idea of the magnitude of the storm, but it's not exactly perfect precision.

Pathway I shoveled to my shed in St. Albans, Vermont.
Along that path 13 inches of snow this week compacted
to 10 inches.

Really big storms - bigger than the one we had Wednesday - are even harder to measure. Compaction, blowing and drifting are all magnified.  Also, storms that have temperatures near the freezing point can be tricky. 

You'll see this over the weekend. We're supposed to get light snow, totally one to as much as five inches, depending upon where you are.

But temperatures in many locations, particularly valleys south of Route 2, will mix with or change to rain or mixed precipitation at times. That'll make meauring what snow does fall a bit challenging

There are standards for how to measure snow.  National Weather Service has a particular way of doing it, and they encourage us to try an emulate the method as best we can.

The NWS lets snow accumulated on a light colored board for six hours. They measure, wipe the board clean, then lets it snow for another six hours, measures again, etc. etc.

Often, this means the depth of snow on the ground is actually less than the official measurement conveyed, because snow typically compacts over the course of a day or more.

One extreme example of this hit in Erie, Pennsylvania around Christmastime. They had an epic lake effect snowstorm there. Over the course of 72 hours ending the evening of December 27 the National Weather Service office in Erie measured an amazing 65.1 inches of new snow.

Even so, the most that was ever on the ground during that period in Erie was only 28 inches. That does seem, odd, doesn't it?

The snow that fell in Erie around Christmas was especially light and fluffy. Such snow really compacts a lot if you just leave it there.

This is an extreme example of how snowstorms can come across in the media as being overstated. We were all blasted by the news after Christmas that Erie had 65 inches of snow. However the actual effects of the storm, while serious, were not an incredible, deadly disaster.

On Wednesday, I measured the new snow we got in St. Albans somewhat close to, but not exactly the way the National Weather Service suggests. It was a good time to conduct this experiment. The snow was light and fluffy. Winds were rather light, so things didn't get too screwed up through blowing and drifting

I came up with a storm total of 8.6 inches. But when I measured the depth of snow on the ground in general about 18 hours after the storm ended, it had compacted a little. There was three inches of snow on the ground before the storm, so there should have been roughly 11.5 inches of snow on the ground.

But I came up with an average of ten inches total on the ground. About an inch and a half "disappeared."

Most people don't measure snow exactly the way the National Weather Service suggest, because they can't devote the time to do so every six hours. Average citizens have to go to work, school, etc. and can't babysit their snow measuring spots like that.

My snowfall measurements that I report to the National Weather Service are likely pretty close to reality, but also probably not perfectly spot on.   And probably none of the snowfall reports in the long list you see after every storm is 100 percent accurate, but they're pretty close.

But the data is still very useful, as I've said earlier in this post.  I also don't want to discourage all those citizen scientists out there who report their snow totals to the National Weather Service and other meteorologists.

Citizen scientists are extremely  helpful in so many ways for meteorologists, and in many other fields. Some of those people who bundle up at 5 a.m. in the morning might become inspired to do even more. Let 'em! We need them.

My only point, every time you look at that list of how much snow everybody got, it'll give you a general idea of the size and scope of the snowstorm.

But if you're bragging that you got more snow than your neighbor because you measured 12.4 inches of new snow and your friend only measured 12.2 inches, the opposite may be true. It all depends upon how you measured.  .