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Blowin' in the Wind, Issue #101 Springtime on the Plains - March 1, 2013
February 27, 2013
Hello ,

The Great Plains - Springtime or not

On the downwind side of mountain ranges, one can generally find dry climates. This leaves a phenomenom known as a rain-shadow and can occur near mountains anywhere, including the volcanoes of Hawaii. If it happens well inland, the climate becomes both arid and continental, which naturally enhances dryness and daily/seasonal temperature variations.

The place where I grew up studying weather is north and east of the western North American mountains. This major cordillera includes the Rocky Mountains, the Kootneys, the Cascades and a few other ranges.

What happens in the springtime in this arid part of the Great Plains? This region includes the Golden Triangle of Montana, the northern Missouri Coteau and the Canadian Palliser Triangle. More generally, it includes a quadrilateral outlined by the cities of Billings, Bismarck, Sasktoon and Calgary, nearly all places within this shape and many near it as well. The months from March to June bring this area the most unpredictable weather at times. What's the most prominent characteristic?


The associated temperature extremes may catch you by surprise. It can be in the 80's (25°C or more) one week and then snow and less than 20°F (-10°C) the next. El Nino and dry springs can lead to droughts and fires. Chinooks occur throughout the year, elevating temperatures and decreasing moisture levels quite quickly. Winds can persist any time of the year, spring included.

One town near this area was half-demolished by fire in May 2011. The strong winds, which had been blowing for days by this point, provided a hopeless situation for regional firefighters. The fire advanced through Slave Lake at a pace of several feet per second at times. In the following months, June and July, the same place endured record-breaking rainfall. Too late, many would say.

When it rains it pours

Drought is not the only type of precipitation extreme. Surprisingly, but not too surprisingly, snowstorms can occur anytime in April and May, often producing an amount ofsnow similar to the total for the previous winter. What happens when an Alberta Clipper stalls? It's no longer a clipper; it's a dump instead. The resulting dense snow cover usually only stays around the flatlands for a few days instead of months, though, offering little time for further accumulation and long-term compaction before melting away.

On the slopes, however, the heavy snow can lead to instability at this time of year. Avalanches in the western mountains take place most frequently during springtime, leading to the greatest number of deaths.

Later in the season, it's rain. If drought is not underway, enormous amounts of rain can land here, and when combined with rapid meltwater usually running off at this time of year, it can flood previously-parched cities like Calgary (2005) and Medicine Hat (2010), taking highways and railroads with their floodwaters.

Spring weather around here is usually quite exciting, not just because the bitter-cold winter weather is behind us, but we never know just what's coming next. Hopefully not drought, though. Even if that kind of weather is pleasant, it can becoming economically disastrous after a while.

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