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Friday is the official start to summer and the season is going to have a really wet beginning for most of Southern Alberta and parts of Central Alberta. A low pressure system from the Pacific will move into the region and additional moisture will be drawn northward, which will lead to widespread rainfall amounts of 50-100mm by Sunday morning. Some are even drawing comparisons between this incoming rainfall to the flooding rains from June 19-21, 2013.

Light rain has already begun to fall across the region Friday morning, but it will it will build throughout the day to a more steady rainfall, mostly in the Foothills. Later in the evening, the steady rain will then start to move into the rest of Southern Alberta from Montana.

The rain will intensify further beginning early Saturday morning, falling at rates that could exceed 10mm/hr, and this is expected to continue straight into the late afternoon in the hardest hit areas. Rates this high will easily lead to over 50mm of rain falling across a wide area.

***Modelled Hourly rainfall rates at 5am CT Saturday, Courtesy of WeatherBell.***

During this time, areas between Calgary and the International border could find themselves in a break in the precipitation, which would result in lower rainfall totals. However, there is some disagreement between weather models on whether this will occur.

The rainfall will then start to weaken late Saturday afternoon to a steady light rain before it dissipates early Sunday morning. By this point, the majority of Southern Alberta can expect to have received 50-75mm of rain and up to 100mm in the Southern Foothills. Parts of the Foothills could see well over 100mm of rain, with some models suggesting that 150-200mm is possible. This is the most extreme case, but the possibility does exist.

On top of all of the rain, wet snow is expected in the Rockies, especially at higher elevations, throughout both Friday and Saturday. Snowfall accumulations could easily surpass 10cm with the amount of moisture this system is bringing to the region.

With this amount of precipitation coming in such a short period of time, flooding is a major concern. Those who live in low-lying areas and/or near waterways should prepare for the possibility of flooding. Luckily, the snowpack in the mountains is considerably less than what it was with the 2013 floods so it’s unlikely that we are looking at a similar outcome with the incoming rainfall. The winds will also be quite strong, with gusts up 80km/h, and with the rain-soaked ground, this could lead to trees being uprooted.