Low-snow (or brown) Christmases

Right now it's less than a week before Christmas, and there isn't much snow on the ground, and so people have been asking about "brown" Christmases.

Global just released this forecast for Christmas day, which is entertainingly specific:

Source: White Christmas Expected In Most of Canada

The typical definition of a "White" Christmas seems to be 1" (2.5cm) or more snow on the ground. And so therefore it follows that a "Brown" Christmas isn't necessarily completely snow-free, but just low-snow.

Is 2017 low-snow in Edmonton?

Edmonton has two main weather stations - Blatchford, and the International Airport.

Following the big December heatwave there's a bit of a discrepancy between the two stations, with 1cm of snow on the ground measured at Blatchford, and 8cm at the International. So as of December 19th in the city we're definitely near zero, but at the International things are just a bit below average.

History of Low-Snow Christmases

This chart shows the history of snowdepth on Christmas day at both Blatchford and at the International. Years that had 3cm or less are highlighted.

Both stations recorded low-snow Christmases in 1987, 1988, 1997, 1999, 2002 and 2005. Blatchford also recorded a few extra in 1959, 1962, 1963, 1988 and 1993, while the International recorded an extra one in 1985.

There is a caveat with the data today, because sometimes Environment Canada will show blanks, and it's not always clear if that is meant to be a 0 or if  data is missing. I've tried to use a consistent approach to clean those up, and looking at the records for these two stations we can see that they usually track each other pretty closely.

The current gap of 7cm between the two stations isn't unusual - there are some gaps in here as large as 10cm or 16cm - but it is unusual for the low-snow years. 1985 is the only similar one, which had the International at 1cm while Blatchford was at 8cm. But for all the other low-snow years here the two stations are separated by at most 2cm of snow.

Fresh Snow (or Rain)

Here we have the amount of fresh snow recorded on December 24th or 25th. There have also been 3 years with rain - 1929 at 0.9mm, 1975 at 0.3mm, and more notably 1989 at 2.4mm.

In 2016 we received 6.6cm of snow at Blatchford and 7.5cm at the International, and that made it a pretty snowy Christmas. That's been uncommon recently though, with 2004 being the last notable Christmas Eve or Christmas Day snow, and before that we have to go back to 1992.

What happens after Christmas?

This chart shows how snowdepth changes over the course of a winter.

It starts by showing all of the winters since 1995 for some context, and then it focuses on the recent low-snow winters: 1997-1998, 1999-2000, 2002-2003 and 2005-2006. 2015-2016 and 2016-2017 are also included here because they're fresh in our memory, and they were relatively low too.

In 1997-1998 the snow took off right after Christmas, hitting 20cm by January 5th. 1999-2000 and 2002-2003 were both a bit slower, but both were around 20cm by January 20th. And 2005-2006 stayed low through January and February, before jumping up to 27cm on March 3rd.

Summary

At this point it's been more than a decade since we've had a low-snow or brown Christmas.

But in 61 years of recordings at Blatchford there have been 11 low-snow Christmases (18% of the time), and in 55 years at the International there were 7 (13% of the time). And the peak era for low-snow Christmases was 1997-2005, with 4-out-of-9 years recording 1cm-or-less of snow at both stations.