Record Watch - Soggy April

As I type this on April 24th, it's snowing again.

A few weeks ago we looked at April Snowstorms, and before that it was April Showers. Today we're going to combine the two, because the International Airport has now recorded more Rain+Snow in April 2017 than during any other April. (and there's still a week to go...)

Here we have the totals of Rain and Snow for April 2017.

Combining the two together we're now well into 1st place with 68.4, above 2nd place 1990 which was down at with 60.6. 

And with 40.2cm of Snow alone, we're currently the 5th snowiest April, still a bit below 1st place 2002 which had 43.2cm. Although again, it's snowing again right now.

Rain+Snow vs. Total Precipitation


Environment Canada tracks 3 precipitation measurements at the Edmonton International: mm of Rain; cm of Snow; and mm of Total Precipitation.

Total Precipitation is usually the sum of the Rain + Snow, but since Snow is fluffy and it's measured in cm, Environment Canada converts that to a mm-equivalent by dividing by 10. So 1cm of Snow = 1mm-equivalent of Precipitation. That's shown in the last line of the example above, with 0.2mm of Rain, 0.6cm of Snow, and 0.8mm of Total Precipitation.

That's how it normally works, but sometimes there's a bit of a discrepancy and Total Precipitation does not quite match Rain+Snow. Here are the comparisons of the two for all of the Aprils at the International:



For a shoulder-season month like April I think it's nice to see the breakdown between rain and snow, but Environment Canada's "official" measurement is Precipitation, rather than just adding Rain+Snow together. And in terms of Precipitation 2017 is at 66.5mm, slightly below the combined 68.4 that we saw above. That's still enough for 1st place though, compared to 1990 in 2nd place at 61mm.

I don't know how Environment Canada decides when there is a difference or not? The largest gap here is 2002, with 48mm of rain+snow, but only 33m of precipitation. The second largest is 1968, at 5mm. And then it drops to the 2mm or 3mm mark, which is where April 2017 is.

This isn't a a huge deal, but to avoid any confusion I wanted to mention it.

Blatchford

The Edmonton International isn't a perfect match for the City of Edmonton, but in recent years the Precipitation data for Blatchford hasn't been great, so that's why I use the International instead.

Blatchford used to have good data though, so here it is, going back to 1881. Strangely enough, at Blatchford the 5 years that had the most Rain + Snow all occurred before records at the International started.

1955 had the most, with 88.1mm. That's still well above our 68.4mm for 2017, although 2017 would fall in the 3rd spot. And there's still a week left in April 2017. And it's snowing again right now.

I'll take a complete look at where April's precipitation ends up next week during the monthly review.