Thereís still a lot of snow on the ground and with cold and dry weather most of this week, there wonít be a lot of melting, but some of the snow is still going to disappear, even at subzero temperatures.
By now nearly everyone knows the statistics. Since the 23rd of January more snow has fallen than would typically be had in an entire winter. Most areas have seen about 100 inches of snow this season, at least thatís whatís in the record books. But if that much snow has fallen, where is it all? Sarcastically you might answer in your backyard, but seriously, where did all that snow go?
Temperatures have been below freezing 22 days since January 23rd. In February alone, Boston has had 62 inches of snow and nearly the entire time has been under 32F. Depending on where you live, most areas have between 20 and 40 inches of snow on the ground.
Some of the greatest snow depths today exist across Essex County. Marblehead has a whopping 40 inches being reported.
While these numbers are impressive, they are less than half what has been reported to have fallen. So, where's the other 50 or even 60 inches of snow gone? How long will it take the rest of the snow to melt? Here are some thoughts on why there isnít more snow on the ground right now and when we might see the grass again.
You might not realize it but snow, which is a solid, can change phases and become a gas, or disappear without ever becoming a liquid. The process, called sublimation, occurs when any solid object goes directly into a gas. Things like mothballs and dry ice can also sublimate over time. The ice cubes in your freezer sublimate, this is why they shrink in the tray. The snow on the ground is sublimating and therefore the depth is decreasing.
Even though itís been so cold, some snow has melted. As the sunís angle gets higher in the sky, the increased solar radiation helps to melt the snow. Even when itís under freezing some snow will melt on south facing areas as well as on the darker surfaces like pavement. Youíll even notice snow melting around tree trunks which are darker and absorb more heat.
How We Measure
If this winter had occurred 40 years ago, the amount of snow measured in each storm would have been less and therefore Boston would not have had 100 inches of snow right now. You might think this is ridiculous, isnít a foot of snow in 1965 the same as foot of snow in 2015? The answer is no.
Decades ago snow was measured differently. Today, we have snow boards. According the National Weather Service, ďA snowboard should be any lightly colored board that is about 2 feet by 2 feet. A piece of plywood painted white works very well. Ideally, it should be painted white to minimize heating by sunlight.Ē These boards are used to measure the snow that falls. They are measured and cleared every 6 hours or 4 times each day. The measurements are then added up and thatís the total amount of snow for a storm. Hereís the problem. This eliminates a percentage of compaction that occurs during snowstorms. This creates inflated snow amounts as compared to older records. Itís not that our snow amounts today are wrong; itís just that they canít be compared to earlier storms or years.
As snow falls on top of itself it compacts and as I just mentioned, you can remove some of this effect by measuring snow more frequently. If we measured snow every hour by clearing the snow board the amounts would be even higher, especially in storms with denser snow. Another reason you donít see 6 or 7 feet of snow on the ground is due to the natural compaction occurring during a storm and in the days thereafter.
When Will We See The Ground Again?
I canít predict exactly when the ground will be exposed, but I donít think spring sports are going to have to be cancelled and hereís why. One thing that is predictable is the strength of the sun. No matter how much more snow we get between now and May, the sun will win.
Back in March 1969 there was 30 inches of snow on the ground in Worcester on the first of March. Even with 7 inches of new snow during the month, there was only 1 inch left when April began. March 1969 was also a very cold month averaging 4 degrees below average. I expect this March to average about as cold.
Assuming 6 to 12 more inches of snow between now and April 1st, the ground should be bare between March 25th and April 3rd. There will still be piles of snow in places, but of the snow thatís here now, nearly all of it will disappear in March. Many spring sports will need to be practicing inside for a while, but unless we have an extreme amount of snow next month, the grass will be exposed only a couple of weeks later than usual.
You can follow more of my forecasting and garden tips on Twitter @growingwisdom