For temperatures we usually use the Blatchford weather station which is located near downtown Edmonton. But the Blatchford weather station stopped recording snow in 2007, and so for today we will mostly be using the data from the International Airport. If Blatchford's historic numbers are available then they will be included for comparison.
In our 2018 in Review - Part 2 - Overall Precipitation we had ended things by looking at how Edmonton's precipitation each year is split between rain & snow, going back to 1880:
For total precipitation 2018 was just a little bit above average with 464mm. And since about 1900 Edmonton's average total precipitation at both Blatchford and the International has stayed in the range of 400-500mm.
And now, let's talk about snow:
Yearly Snowfall History
Here we have the snowfall totals each year for Blatchford (1880-2007) and for the International (1961-today). In this chart there is a darker grey section from 1961-2007 when both stations had reliable data, and that darker section is the difference between the two stations. In some years Blatchford was higher, while in others it was the International.
For 2018 the total snowfall at the International was 165cm. That puts 2018 in 10th place for the International, and the most snow since 187cm in 2013. But it is well below some of the really big years like Blatchford's 287cm in 1935, or 225cm in 2003.
On average we get about 125-130cm of snow each year, and that has stayed reasonably consistent since about 1900 or 1920. This year's 165cm was above that, mostly because of a ridiculous September.
Monthly Snowfall
Here we have the snowfall each month for the last year-and-a-half.
Normally when we talk about snow we split it into Winters rather than Calendar Years. And so for most of the charts today the calendar year 2018 will be split between the back-half of the winter of 2017-2018 and the front-half of the winter of 2018-2019.
This chart uses a format that we will be seeing a few times today, with the recent average as a white line in the middle, and it is surrounded by a darker-blue band for the 25th-75th percentiles (where things will fall roughly half of the time), and that is surrounded by the recent extremes (highest, second highest, second lowest, and lowest since 1995).
The spring of 2018 wasn't particularly snowy - March was a little high at 28cm, but April only had 12cm. In May we didn't get any snow, and that only happens about half of the time.
The fall of 2018 was more interesting. In September 2018 the International got 38cm of snow, while its previous record for September was 13cm from 1965, and Blatchford's record was 28cm from 1926. That also made September the snowiest month of the year for 2018, and that had never happened before. We talked a lot about our record-breakingly-snowy September here.
October's 8cm was right on the average, although about 1/4 of the time we make it through October without recording any snow. November's 17cm was a bit below the average of 20cm. December's 31cm was quite high at about double the average of 16cm, but still well below a year like 2009 which had 46cm.
Days with Snow
Here we have the number of snowy days each month, and 2018 is again split into January-June in Red and July-December in Blue.
For the end of the winter of 2017-2018 the months were typically-snowy, although March was a little high at 11 days compared to an average of 9.
For the first half of the winter of 2018-2019 the story really was September, which had 8 snowy days when the previous record was 5. October was also pretty unusually snowy with 6 days, although that was below 2008's 9 days.
Cumulative Snowfall (so far...)
Here we have the cumulative snowfall as it adds up over the winter, and 2018 is again split into January-June in Red and July-December in Blue.
For the end of 2017-2018 the snowfall was pretty average, with the red line tracking the line for the average very closely.
For 2018-2019 things got off to an early start with the very snowy September. Since then things have been more average, but overall the total for this winter is still very high because of that initial boost from September.
Large (5cm+) Snowstorms
In this chart each of the bubbles represents a large snowstorm that dumped at least 5cm+ onto the International Airport. These are not necessarily single-day snowfalls, because sometimes snow falls over the course of a few days. We talked about this more (and looked at records) back in Edmonton's Largest Snowfalls.
Here 2018 is again split between the back-half of 2017-2018 and the front-half of the winter of 2018-2019. The large snowfalls from 2018 are labeled in red, with the total snow, the number of days, and the end date.
A few years ago we looked at how frequently Edmonton gets giant snowfalls, and we saw:
- 10cm (4"): usually about 2-5 times per year
- 20cm (8"): maybe every-other-year (our last one was 24cm in the middle of April 2017)
- 30cm (1'): none in the last decade, 3 in the last 30 years.
In 2018 we had a total of 11 5cm+ snowfalls.
- The largest was 21.9cm over 3 days at the beginning of December.
- We had 6 more storms in the range of 10-16cm.
- And then there were 3 more from 5-10cm (although 2 of those were 9cm and 9.8cm, so almost 10cm, but not quite)
So 2018 had a total of 7 10cm+ snowstorms, plus 2 more which were right below the cut-off. That is not record-breaking, but it makes 2018 one of our more snowstormy years.
Snowdepth So Far
This chart shows the snowdepth measured at the International, and 2018 is split into January-June in Red and July-December in Blue.
Looking at the red line for last winter, normally our big spring melt starts in the first 2 or 3 weeks of March. We talked about that here. But March & April of 2018 were both really cold, and so we held onto the winter snowpack for a long time. Things didn't start dropping until mid-April, which was the latest of any year since 1995. We reached 0cm on April 21st which is pretty late, but was still earlier than years like 2013 (April 27), 2011 (April 29), or 1992 (May 2).
In the fall the blue line was off to an early start in October, then it took a break for a few weeks, and then it came back right at the beginning of November. The 21.9cm storm at the beginning of December pushed the snowdepth way up, but a lot of that melted-off during the warm December. By the end of the month our snowdepth was sitting at 22cm, which was just above the 75th percentile, and well above the 9 cm that we had at the start of 2018.
The Spring Melt
Here is another look at the spring melt of 2018, and it was not the latest year here, but it got a very late start.
After the snow hits 0cm for the first time there is always the chance of some more late, spring storms, but the snow from those usually only hangs around for a few days.
Autumn Snow
And here is the snow on the ground for the fall of 2018.
2018 was the only recent year to start October with almost two weeks of snowcover. That melted-off and then we were snow-free for a few weeks, but then the lasting snow showed up at the beginning of November.
This chart shows all of the snowfalls from September 1st through December 31st at the International Airport. The bubbles in orange show snow that melted-off, and the bubbles in blue are for once snow started to hang around. We looked at this in more detail in First & Lasting Snow.
2018's first snow on September 18th was quite early, and actually 2014, 2016, 2017 and 2018 all had September snow. The last time that 3 years in-a-row had September snow was 1983-1985, and the last time it happened in 4-out-of-5 years was way back in the early 1970s.
2018's lasting snow arrived on November 1st, which was one day later than in 2017 when it arrived on Halloween. Both of those years were early~ish, although about half of the time we get our lasting snow in the last week of October of first week of November.
From Spring Melt to the First Lasting Snow
This chart tries to show how long Edmonton is snowfree for each year, and it gives us two different choices for what exactly "snowfree" means:
- Snowfree could mean between when the winter Snow first melts down to 0cm to when we get our first lasting snow. This ignores any late-spring or early-autumn snowstorms, because most of those will melt off quickly.
- Alternatively snowfree could be more strict, and it could mean from the very,very last snow on the ground in spring to the very first snow of autumn.
In 2018 the snow first melted down to 0cm on April 21st, which is 3 weeks later than the average of April 1st. In 2017 the snow hit 0cm on March 29th, and 2016 was a really early melt on March 13th. So 2018 was pretty late, but 2011 and 2013 were later.
In 2018 the final spring snow was right after the melt, on April 23rd. That's a few days before the average of April 29, and about half of the time we will get some snow in May.
2018's first fall snow on September 12th was a week earlier than the 5-Year average of September 21st. Although that average had been really dragged-down recently by the early snows in 2014, 2016, 2017 & 2018. A decade ago the 5-year average for the first snow was more than a month later on October 27th, because for 2007-2011 the first snow waited until the last week of October or first week of November.
2018's first lasting snow on November 1st was about a week before the average of November 8th.
When we look at the averages the spring melt and final spring snow at the International are 1-2 weeks earlier than they were in the 1960s. But the first fall snow and lasting snow are actually a week earlier than they used to be.
Finally for today, here we are looking at the total length of the snowfree period each year at the International Airport. And again we have two definitions of "snowfree": from first melt to lasting snow; or completely snowfree from the very last snow on the ground in spring to the very first snow of autumn.
In 2018 the International went a total of 142 days (about four-and-a-half-months) completely snowfree, from April 23rd to September 12th.
- 142 days made this the 18th shortest year (out of 57).
- Since the 1960's the average has been around 160 days, although that's dropped a bit recently with 2014, 2016, 2017 & 2018 all being quite short.
- The very shortest year was 1992 with only 90 days, from May 23rd to August 21st. Recently 2014 had 126 days and 2002 had 118.
- The very longest year was 1988 with 209 days from March 31st to October 26th. Recently 2011 had 197 days and 2008 had 190.
Completely snowfree days are a nice and precise measurement, but any year can get a bit of snow late in the spring or early in the fall without feeling particularly wintery. So I prefer the length between the big melt and lasting snow, where we are free of "permanent" snow.
In 2018 the International went a total of 194 days/6.5 months without "permanent" snow, from April 21st to November 1st.
- 194 days made this the 7th shortest year.
- Since the 1960's the average has stayed very steady at around 210 days/7 months.
- The very shortest year was just a few years ago in 2013 with only 183 days, from April 27th to October 27th.
- The very longest year was 1981 with 259 days, from March 25th to December 9th. Recently 2016 was 5th-longest with 247 days from March 13th to November 15th.
And that brings us to the end of the 3rd-and-final part of the giant Edmonton Weather Nerdery 2018 in Review.
If you are wondering what previous Precipitation years-in-review looked like:
No comments:
Post a Comment