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Weather: Slowly cooling down

Forecast covering the period from Sept. 15 to Sept. 22

This map shows the amount of precipitation that has fallen this growing season (April 1 to Sept. 8) across the Prairies as a departure from average. A quick look at the map shows most areas were below average (browns), with only the areas near Regina, along the foothills southwest of Calgary and a small portion of the Peace River region receiving above-average amounts of precipitation.

Well, what can I say? Thanks to an upper low that crossed the northern Prairies last week much slower than originally anticipated, the rest of the forecast kind of fell apart. That’s the tricky thing with forecasts: one change to a big system can have significant impacts further down the road. On a positive note, the cold weather predicted for the middle of the month looks not quite as cold.

For this forecast period, the weather models show weak high pressure in place on Wednesday, Sept. 15, bringing sunny to partly cloudy skies along with daytime highs in the low 20s. On Thursday it looks like an area of low pressure will develop to our southwest and quickly move to the northeast, bringing clouds along with the chance of a shower. This system is forecast to intensify as it moves over Hudson Bay, which will allow colder air to push southward behind it.

Just how far south this cold air will make it depends on the strength and timing of a second area of low pressure forecast to develop over Alberta and push eastward over the weekend. The system doesn’t look like it will produce much rain, with only a mix of sun and clouds and the odd widely scattered shower. Temperatures should warm up in the southerly flow ahead of this system, with highs over the weekend making it into the upper teens to possibly 20 C in areas that receive more sunshine. Friday morning could be on the cold side, with some areas seeing temperatures flirting with the 0 C mark if the southerly flow is slow to develop.

We will see a slight cool-down to begin the week of Sept. 20, but with weak low pressure forecast to be in place the cloud cover should keep overnight lows well above the freezing mark.

Usual temperature range for this period: Highs, 13 to 24 C; lows, 2 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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