Ag Weather Forum

Potential Increases for Frost or Freeze in Canadian Prairies

Joel Burgio
By  Joel Burgio , DTN Senior Ag Meteorologist
Looking at the model maps, a ridge to the west will block systems and direct the air mass flow into Western Canada. Originating over northwest Canada or eastern Alaska, this is a somewhat colder flow than if systems come into the region from either the Pacific Ocean or from the U.S. (Penn State Meteorology graphics)

The recent weather across the Canadian Prairies has more often than not featured near- to well-above-normal temperatures. This limited the areas that have experienced frost or light freezing conditions and allowed continued development of late-filling crops in the region.

However, there are indications today that this may be changing.

The change is such that the chances for frost and even a freeze in the region will increase, especially during the eight-to-10-day forecast period. It is not unusual for this area of Canada to experience frosts or freezing conditions during the last part of September, for some areas it is actually normal for frost at this date or even sooner. However, with the lateness of the crops, especially canola, it was hoped that late frosts would result in higher production and better quality of the delayed crops.

The upper level charts that are shown here is a mean of what is expected during the period Sept. 26 through Sept. 28 from the European and the United States forecast models. The main features as we look as these maps are the building ridge pushing northward into the Gulf of Alaska and the mean trough position split between troughs in the western U.S. and over central Canada. The ridge to the west will serve to block systems from coming inland off the Pacific Ocean and at least briefly turn the flow more from the northwest or north-northwest over Western Canada. The trough to the east, in central Canada, also intensifies this affect, somewhat. The arrows indicate the potential direction of flow during that time frame.

This means that air masses coming south into the Canadian Prairies originate over northwest Canada or east Alaska which is a somewhat colder flow than if they came into the region from either the Pacific Ocean or from the U.S. The longer the Gulf of Alaska ridge continues, the colder these air masses would become. Since this is a new feature today, this is to be viewed with some caution. However, the time of year dictates that any time the flow turns around from the north there would be the potential for frost or freeze conditions in the Prairies.

The change in the weather pattern being advertised for the end of September and early in October is likely to bring with it a frost and may also include a freeze for some locations. The highest risk would be in Alberta crop areas and possibly northern areas of Saskatchewan. If this pattern holds for any length of time, with the ridge in the Gulf of Alaska, more of the Prairies would likely turn much colder. However, it is too soon to tell if this would be the case, but is does bear watching. Freezing conditions would threaten to cause some damage to late-maturing crops or to affect quality somewhat. This will depend on how far-advanced the crop is when this colder weather arrives.

Joel Burgio can be reached at



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