Ag Weather Forum

Rain and snow during the spring has left much of the northern Alberta and northwest Saskatchewan area too wet for farmers to get into the fields and harvest the remaining crop from last season.

In addition to this, the region recently turned quite cold which limits the potential for these fields to dry out. The cold weather pattern is expected to continue for a few more days before a more moderate temperature pattern begins to develop.

The forecast during the next seven days shows only limited amounts for precipitation in the area during this timeframe, which may help somewhat as well. The map included with this article shows the rainfall forecast during the seven-day period, in inches. The amounts predicted for the area in question look to be about 0.40 to 0.50 inch or 10 to 13 millimeters. This occurs mostly during the period Sunday into Monday with drier weather preceding and following this period.

The weather pattern has two aspects to it at this time. The first is an active southern branch jet stream likely influenced by marginal El Nino conditions in the eastern Pacific. This is primarily the reason for the heavy rains being predicted over the U.S. plains, Midwest and Delta areas, although it is also enhanced by the contrast in air masses between the warm and moist air trying to come northward seasonally and the unusual cold air mass moving southward out of Canada into the U.S. region.

The first question then would be do we expect this type of heavy rain to move northward and affect the Canadian Prairies region? The answer is somewhat uncertain at this time. Seasonal warming over the southern U.S. should force the southern branch jet stream northward with time and eventually this could bring rains to the south and east areas of the Prairies grain belt.

However, this process has been slow to occur and recently has actually trended more towards the south than the north. We might also lose the cold air mass potential in Canada which would reduce the heavy rain aspect of this pattern somewhat. We will keep an eye on the U.S. rainfall to see if we can detect a northward shift during the coming weeks.

The second aspect of the pattern has been the persistent mean trough over or just west of the British Columbia coast in the Pacific. This trough has been sending waves of low pressure into Western Canada for a while now.

These troughs and surface low pressure systems are the primary reason for the above-normal spring precipitation in the northern Alberta region. The moisture has a hard time crossing the Rockies, but enough of it does to bring precipitation to these northwest areas while leaving areas to the south and east somewhat drier.

This trough may weaken somewhat as we move through the spring, reducing the threat of further moderate or heavy precipitation in the area. We may actually see the south and east areas getting wetter with time while the north Alberta and northwest Saskatchewan area turns drier. This is due mostly to seasonal changes expected during the spring months.

A final aspect of this pattern is the high latitude blocking that has been coming and going during the winter and spring season. This high latitude block forces the polar vortex southward and this in turn provides the cold weather that has been complicating the weather picture for the region.

High latitude blocking is difficult to forecast much in advance. However, most agree that high latitude blocking becomes less important in the overall weather picture during the spring and early summer period. In the short-range outlook, this cold pattern will be important, but in the longer-range outlook it may be of less importance.

Joel Burgio can be reached at joel.burgio@dtn.com

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