Ag Weather Forum

The seemingly endless stretch of winter weather across the Canadian Prairies continues to raise concerns of major spring flooding and delay the start to the planting and growing season.

Temperatures have remained unusually far below normal for a lengthy period of time, with temperature departures across the region for April from between 3 and 6 degrees C (6 to 10 degrees F) below normal from Alberta to 5 to 8 degrees C (10 to 16 degrees F) below normal across Saskatchewan and Manitoba.

Many areas are seeing daytime temperatures struggle to get very far above the melting point with nighttime conditions well below freezing. The low temperatures initially were a product of a strong blocking pattern in the upper atmosphere across northern Canada during much of March and early April, but during the past several days the block weakened and almost disappeared.

So why is it still cold with still a little snow in the forecast for early next week? The upper air pattern that has evolved since the blocking pattern has weakened is one that has brought an upper air trough to Western Canada. This allows cold air to continue to drain southward from northwest Canada, while also allowing storms to travel through or just south of the region.

Even as we pass the mid-point of April, the snow cover and the water contained within it from central Alberta to south-central Saskatchewan and western Manitoba remain unusually high. The snow water equivalent or SWE across these regions ranges from 80 to more than 120 mm (3.1 to 4.7 inches) as of April 15. Snow depth amounts have lowered some during the past week despite some new snow, but this is due mostly to the snow cover settling and compacting rather than melting. Much less or little snow remains across southern Alberta, southwest Saskatchewan and far southeastern Manitoba.

The threat for spring flooding continues to increase, as it is inevitable that temperatures will rise during the next few weeks, possibly to levels that could bring on a rapid meltdown. Temperatures may at some point bounce back to just normal levels, which would send temperatures to above the melting point for much of the day and night in many areas. Current forecasts from some of the more reliable computer models show a relaxation in the cold pattern during the second half of next week, with western areas possibly seeing readings jump to above-normal levels.

At the current time, the potential warm-up looks to be accompanied by mostly dry weather, but the commencement of a rapid snow meltdown could bring on developing flooding later this month or early in May. Recent heavy snows through parts of Montana and North Dakota also raise a red flag, as many of the rivers across the eastern Prairies flow northward from the U.S.

With the snow cover still extensive and deep, and with a significant flood season appearing more likely as each day goes by, delays to the start of spring fieldwork and planting are now a foregone conclusion. Further clues to the extent of the potential flooding should become clearer during the next week or two as the weather pattern begins to turn into more of a spring pattern.

Doug Webster can be reached at doug.webster@telventdtn.com

(CZ/ES)