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Forecast: Seasonably mild with a chance of snow

Issued December 11, 2017: Covering the period from December 13 to December 20

For this article I’ve gone back to redoing Environment Canada’s snow depth map. The original is a black and white map that can often be very difficult to read due to a lot of overlapping data. I have to do a lot of cleaning up to try and make the map readable and in the process, a fair bit of detail is lost in some regions — especially Alberta, where snow cover often changes significantly over relatively short distances. Snowfall amounts are very light over the southern third of the Prairies, with the heaviest snow cover confined to the northern regions.

The weather models continue to struggle with the finer details of the overall weather pattern. Take last week’s forecast: the weather models were able to correctly predict the development of the West Coast ridge along with the broad trough of low pressure across the eastern half of North America; what they struggled with was the strength of each of these features. As it turned out, the western ridge ended up being much stronger than expected and, instead of our region being deep into the cold air associated with the eastern trough, we ended up seeing much more of the warm air from the western ridge.

For this forecast period, it looks like the western ridge will slowly break down, allowing the weather pattern to switch to a more westerly or zonal flow. This will keep us in mild winter weather with better chances of seeing measurable snowfall.

To begin this forecast, we’ll still be in a strong north to northwesterly flow that will see one more weak area of low pressure come zipping across our region. This system will move through on Wednesday, bringing clouds and mild temperatures, along with a few flurries, especially over eastern regions. We’ll see a slight drop in temperatures on Thursday and Friday behind this area of low pressure, but overall, it will remain mild. The next area of low pressure will begin to develop to our west on Friday, then track eastward over the weekend as the western ridge breaks down. Confidence in the exact track and strength of this system is not high, but part of southern and central Manitoba will likely see at least a few centimetres of snow as it passes through.

With the breakdown of the western ridge the weather models have another low quickly moving in off of the Pacific and racing across the southern Prairies, bringing with it a quick shot of snow on Monday. It looks like skies will clear out on Tuesday and Wednesday ushering in a period of nice seasonable mid-December weather.

Usual temperature range for this period: Highs, -19 to -2 C; lows, -28 to -11 C.

About the author

Co-operator contributor

Daniel Bezte

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the U of W. He operates a computerized weather station near Birds Hill Park.



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