Ag Weather Forum

The recent weather pattern over the Canadian Prairies has featured above-normal temperatures in western locations while eastern areas have seen more cool weather. The short-range forecast covering the five-day period suggests that this pattern will begin to change as the west turns somewhat cooler and the east becomes warmer. The longer-range charts covering the eight-to-10 day forecast period suggest that this pattern of cooler west and warmer east will continue.

The eight-to-10 day forecast charts from today's European, U.S. and Canadian weather models show the mean pattern in the upper levels of the atmosphere for the end of next week, Thursday through Saturday June 16 to 18. The most interesting aspect of these maps is the trough-ridge-trough pattern across southern Canada. The trough position in the west is centered off the West Coast mainly due west of Vancouver, but does extend to a secondary trough located over northwest Canada and the eastern Alaska area. The strongest trough is the one depicted on the Canadian model which is the farthest to the right map in this series. This trough represents a source region for disturbances moving inland off the Pacific during this time frame.

The mean ridge position on these maps is best indicated using the red shading and as you can see the coverage on this ridge is from Manitoba eastward across Ontario and northward through Hudson Bay into northeast Canada. This ridge suggests a tendency for warm weather aloft, which will translate to drier and warmer-than-normal weather in the area covered by the red shading. The ridge also serves to deflect the disturbances coming out of the western trough towards the north. The cold fronts associated with these disturbances may continue to move east into Manitoba, but they would be weakening as they did and therefore the shower activity would be on the lighter side and the temperatures would only change a little as these fronts enter the region.

The jet stream in the area is essentially depicted by the tight packing of the contour lines between the trough and the ridge. This jet stream begins near the bottom of the trough and moves northeast cutting southwest to northeast across the Canadian Prairies. This jet stream will divide somewhat cooler weather moving southward over Alberta from somewhat warmer weather moving northward through Manitoba and Ontario. Saskatchewan is a swing area and could go either way. The European model, the map at the left, shows a farther west position on the jet stream and therefore a farther west penetration of the warmer and drier weather.

Model agreement, though not perfect, is fairly good for this time period. This means the confidence on this weather pattern verifying is relatively high. This should be a favorable weather pattern most crops in the region as areas in the west and north, where it would be more likely to be cooler and wetter, would benefit. The warmer and drier weather over southeast areas should mostly favor developing crops as well, so long as this ridge pattern does not last for a very long time.

(CZ)

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