As we move through the middle of August and with crop development still running behind normal, we continue to keep an eye out for any significant early season cold that might impact the region. The forecast maps suggest that the coldest weather relative to normal for the Canadian Prairies region might actually occur during the next five days, which might be a little too early for the air mass to get cold enough to do significant damage.
Forecast maps on Aug. 15 show a significant pool of colder-than-normal weather expected to move over northwest Canada during this period. There is currently a building surface high over Alaska and a deepening trough over far north Canada. The northwest-to-southeast flow between these two features is expected to transport this colder-than-normal air mass southward towards the Prairies.
In the day-by-day breakdown, the coldest air is expected to move over the Prairies between this coming Saturday and Sunday mornings. If this were to occur a few weeks from now, this would most likely result in a significant cold weather event for the region, affecting any immature crops. As it is, coming during the mid-August period, we have the calendar working against a major threat. However, we could still see low temperatures dip into the 30s Fahrenheit in some key growing areas for canola, most notably in northwest and central Alberta. However, right now, a damaging event is not expected. Crop development will be slowed down, of course.
The pattern that has contributed to this cold event appears to be breaking down, following this weekend. The ridge that is currently located over the Aleutians and southwest Alaska is expected to be gradually replaced by a trough. The north Canada trough continues during this period. As a result, the wind flow turns from the west over southern Canada, during the last part of the 10-day period. It remains a fairly strong jet stream for this time of the year, which means temperatures north of this jet would still average below normal; but, with west-to-east flow, the southward push to any cold weather would be rather limited.
Also, without an upper level ridge in Alaska, the development of strong surface highs would also be limited. The bottom line here is that temperatures are likely to vary somewhat under this fast flow aloft, but extreme cold events would be less likely, assuming this pattern verifies. We have noticed that that weather patterns featuring either above- or below-normal temperatures for the Canadian Prairies have not lasted very long before changing again this season. The Alaska high has also shown a tendency to re-form and move back into the picture. So, if these is another break down in this flow pattern, it could very well lead to a problem for late-developing crops.
I expect, at this time, that the cold weather moving over the region this coming weekend will not be cold enough to cause significant problems for crops, outside of possibly the Peace River region. This area has already had lows near freezing, and this air mass could be at least be that cold, possibly colder.
It appears that following this cold event the temperatures will moderate during the six-to-15-day period. However, with the weather patterns we have noticed this season to date this will need to be watched for any signs of a turn towards colder conditions.
Joel Burgio can be reached at firstname.lastname@example.org
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