Forecast: Cold with slight chance of snow

Covering the period from October 21 to October 28

This map shows the snowfall departure from average for all La Niña winters (1950-2009), based on analysis at the Climate Prediction Center using Rutgers gridded snow data. Blue colour means above-average snowfall, while browns are below average. Most of southern and eastern Manitoba show above-average snowfall in La Niña years, with amounts being greater by about four to 12 inches (10-30 cm).

Once again, the weather models did a pretty good job with the medium-range forecast. The northern Manitoba low stalled out as forecast, and we saw the resulting surge of cold air push southward, bringing an abrupt end to the seasonable fall temperatures. The only thing the weather models got wrong was that the daytime highs ended up being a little cooler than forecast, and the overnight lows were a little warmer.

For this forecast period, it looks like we are going to be stuck in the same cool northwesterly flow that established itself last week. Looking at the big picture, there is a large trough of low pressure over Eastern Canada, with a ridge of high pressure just off the West Coast. This means the jet stream will be riding over the western ridge, then diving southeastward under the eastern trough. This means we will stay in a predominantly northwestern flow, which should keep us cooler than average right through this forecast period. Expect daytime highs to be in the +1 to +3 C range, with overnight lows falling into the -6 to -9 C range, which is colder than the usual temperature range.

There will be the odd weak area of low pressure that rides over the western ridge and dives southeastward across our region, but this setup does not really allow for any strong storm systems. The best chances for precipitation look to be over the weekend, with any precipitation likely falling in the form of snow and any amounts looking to be light. The next chance for precipitation looks to be around the middle part of next week (Oct. 27-28) as warm air tries to push northward ahead of a strong Gulf of Alaska low. Currently it looks like we will see daytime high temperatures rise to around the +10 C mark.

Looking further ahead to the Halloween weekend, the weather models call for the warm temperatures to continue, with daytime highs expected to be around +10 C and overnight lows staying slightly above freezing.

Usual temperature range for this period: Highs, 4 to 15 C; lows, -6 to +4 C.

Probability of precipitation falling as snow: 40 per cent.

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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