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Forecast: Slow warming trend expected

Issued August 4, 2017: Covering the period from August 9 to August 18

Last week’s forecast quickly fell apart, at least from the point of view of temperature, as the upper low that brought some much-needed rain to western regions also altered the upper-level flow.

The upper low combined with the building ridge of high pressure over extreme western North America shifted our flow from west-northwesterly to more of a northwesterly northerly flow. This allowed much cooler air to work into our region, especially in the upper atmosphere. While high pressure mostly dominated at the surface, as expected, the cooler upper-level air allowed for afternoon clouds along with the odd shower or thundershower to develop.

Before we get into this week’s forecast I should mention that confidence in it is lower than usual since I had to write it four days earlier than normal as a result of the long weekend. That said, I figured I’d give it the old college try anyway!

For this forecast period it looks like we’ll continue to be slightly cooler than average, with daytime highs in the low 20s and overnight lows around the 10 C mark or even a little cooler. By later in the week a large area of high pressure is forecasted to build across the Prairies, stretching from northern Alberta southeastwards into the central U.S. This high should bring mainly sunny skies along with slowly warming temperatures, as warmer air slowly gets pulled up from the south on the western side of the high and then wraps itself around the high. We should see temperatures in the mid-20s by Friday or Saturday with mid- to upper 20s expected over the weekend.

This high is then expected to weaken and move off to the east early next week. This will open the door for several weak systems to begin pushing in from the west. With plenty of warm air and humidity in place we can expect to see scattered showers and thundershowers during this period. That said, this far out, confidence in the timing of these systems is very low.

Usual temperature range for this period: Highs: 20 to 29 C, Lows: 8 to 14 C.

About the author

Co-operator contributor

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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