Weather5280's 2015-2016 Snow Season Forecast Review

Well, we've made it. May is finally here, and (even with our recent chilly weather) our snowfall chances decrease markedly with each passing day as we head deeper into the month and on into June. On average, Denver sees 1.7" of snow in May, which makes the month the city's second least-snowiest month of the snowy season behind September (1.0" average). While we still see a few models producing snowfall at higher elevations on Denver's south and west ends at times, the threat for any significant snowfall at lower elevations is quite low as we head through the remainder of May.

With that, it's time to look back at the 2015 - 2016 snowfall season, which began way back in September of 2015, and continues through the end of the month. If we happen to see a late-season snowfall, it's doubtful it'll impact any of these numbers or thoughts too much.

Barring any additional snowfall at Denver International Airport, Denver will end the 2015-16 snowfall season with 72.8" of snow, several inches above the long-term average of 57.1" (1882 - 2015).

The least snowy months this season were September and October, both logging 0.0" at the airport. The snowiest month was March when 18.4" of snow fell, followed closely by April at 15.6". Remarkably, of the nine months in Denver's "snow season", five of those recorded above normal snowfall:

Monthly snowfall totals for Denver, CO 2015 - 2016 season (blue!) vs normal (orange!) | Weather5820

Winter 2015-16 Forecast Grade
In the end, we actually think this season's outlook worked out a bit better than last season, largely due to the fact we put a greater emphasis on the fact that it would not be a cold season overall. That, coupled with a pretty good snowfall forecast showing puts this season's overall grade at an A. Some of our biggest hiccups with this season came within the season itself, with several challenging forecasts – namely that big March blizzard which delivered over two feet of snow for many metro area locales.

Snowfall: A
During the first few days of November, Brian Bledsoe issued an update on our winter season outlook. In it he said this:

My favored analogs do offer some decent snow for Denver...generally normal to a bit above normal:

  • 1957-58: 57.1"
  • 1997-98: 72.1"
  • 2009-10: 60.6"
  • 2014-15: 57.8"

I think that Denver will end up in the same range before winter 2015-16 is done. However, I believe that most of that will come during the back half of the winter.

A big takeaway from above, is that we emphasized time and again that the back half of the winter had the potential to really pile the snowfall totals up, and that the threat for a big snow or two was elevated this season. After a warm and dry February, things certainly looked bleak, but we assured you all that March would transition back to a stormier pattern. With this considered, 62.6% of our total seasonal snowfall came in the three month period of February, March and April, with 45.6" of snow being recorded over this three month period. This means that just 27.2" of snow were recorded during the first five months of the snowfall season.

In many respects, 1997-98 wasn't a great analog for the U.S. this winter, while in others it certainly was. Should we have taken purely at a snowfall totals level, it certainly worked out very well. As the season progressed, the 2014-15 analog became more and more favored. In a lot of ways, we saw a very similar end to the season this year as we did last – the big difference being that temperatures this year supported more snow versus rain, where last year many systems that came through during March and April ended up a degree or two too warm for snow in the city.

Lastly, we again thought this season would at times really favor some of our readers south of Denver for snowfall. This too worked out very well, as Colorado Springs hit the 50" mark for the first time since 2000-01 this season.

Temperatures: A+
If there was one takeaway we left you with at last fall's weather meet up, it was that we didn't expect this winter to feature colder than average temperatures, basically anywhere. There were periods of cold, to be sure (it's winter), but overall this winter was a warm one for the United States.

From our November outlook:

There are other models out there too, such as the JAMSTEC that is forecasting it to be a cold and wet winter from start to finish. I just don't see how we are going to get the cold air and be able to sustain it for the whole winter. Will we get cold shots here and there? Of course, even last winter which ended warmer than normal we had some very cold spells.

Early on that heat was focused in the east:

Which then shifted to the west of February:

And a look at December through February shows overall coast-to-coast warm:

Statewide: A
Late last summer Matt Makens spent time time breaking down El Niño facts and figures as they relate to winter in Colorado. There are a lot of misconceptions out there of what a "typical" Niño winter means for us, and who in the state will see how much snow when. In many respects this is due to the fact that no two Niños are the same – but also the long-held idea that a Niño favors southwest Colorado for snow and the northern mountains for dry. In fact, the core winter months (Dec - Feb) are very typically quite dry for all of our mountains during a Niño year, and overall a Niño vs Neutral vs Niña only helps tilt the scales one way or another, but not all that decisively in many cases.

Early in the season there were a lot of folks calling for an epic winter in the southwest, while we said not so fast... In fact, near typical peak snowpack (early April) southern Colorado basins were reporting some of the lowest numbers in the western U.S.:

Statewide snowpack did "just fine" this season, thanks in large part to a strong snowfall season for the northern basins. Through late February statewide averages hovered near to just above normal, before our prolonged dry-spell evened things off for a few weeks to end February. Much of March was spent playing catch up, with snowpack nearing normal to end March, but then dropping off dramatically at peak time (April 9). In April you can clearly see the impacts of a couple good storms, with snowpack now dropping off rapidly as the warm season sets in (2015-16 in dark blue). Thankfully, this season looked much better as a whole than last season (light blue):

California
It feels like forever ago now, but remember when the Godzilla El Niño was gearing up to drown California? Well, in more was than one this El Niño failed to live up to the hype, and drought relief in California was one of them.

While there certainly were improvements, today only 4.27% of the state is not experiencing Abnormally Dry to drought conditions (up from 0.14% a year ago). That means that 95.73% of the state continues to experience drought conditions, with still nearly half (47.92%) of the state experiencing Extreme Drought or worse as classified by the U.S. Drought Monitor. So, while there have been improvements in recent months (see May 2015 left, May 2016 right below), this El Niño winter left a lot to be desired across the western U.S. and California, where drought relief is so desperately needed.

Drought comparisons | End May 2015 left, end May 2016 right | US Drought Monitor

Wrap
As we head into the warm season, large-scale shifts will continue to dominate the headlines. As we discussed earlier this month, El Niño is fading and La Niña may be just around the corner and this will of course have impacts on our weather as we head into the summer months and eventually begin planning for our next snowfall season across Colorado.

For now we take a break and enjoy the spring-like temperatures and always appreciated showers and storms that we often see this time of year. As you can see in the drought image above, recent times have been good for Colorado, though drought conditions are never too far off in this region of the world.

Brendan Heberton

Brendan is founder of Weather5280. He is co-founder of FreshyMap, and develops software for geospatial data analysis and visualization.

Denver, Colorado
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