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Fall 2017 forecast (and a first look at winter)

The Weather Network logo The Weather Network 2017-09-21
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The summer of 2017 will be remembered very differently, depending on which part of Canada you call home.

In the West, scorching heat and persistent dry conditions prevailed, as temperature records fell and places like Vancouver saw an unprecedented streak of rain-free days. Further east, rain was more abundant (even excessive), particularly across eastern Ontario and Ottawa Valley which saw one of the wettest summers on record. Frequent showers and storms were accompanied by a lack of persistent heat.

Meanwhile, Atlantic Canada saw temperatures close to normal for the season, though the influence of tropical moisture kept the weather on the wet and muggy side at times, especially near the coasts.

Now that summer has run its course, we turn our attention to the next three months, to see what the fall season has in store. We have all the details below (and a preliminary look at winter temperatures as well) in The Weather Network's 2017 Fall Forecast, which covers the months of September, October, and November.

National Fall Overview

We expect that the fall season will feature near normal or above normal temperatures across all of Canada. However, fall is well known for its temperature rollercoasters, and it is rare for any region to lock into a pattern for most of the season. Regions that are warmer than normal for the season will still see periods of cold weather, but the periods of mild weather will outweigh the periods of cooler weather.

Fall map © The Weather Network Fall map

A good example of this can be seen in our pattern map shown below, for mid to late September. This map is quite different from the map for the fall season as a whole, especially across western Canada.

Fall map © The Weather Network Fall map

Regional Temperature Specifics

From the Great Lakes to the Maritimes we have already seen several shots of autumnal weather during August and early September, which has brought a premature end to the growing season in many places.  However, warm weather is not gone for good across this region.

Fantastic fall weather is expected to dominate mid and late September and continue well into October, providing more than the typical number of warm sunny days and great opportunities for outdoor activities and enjoying the fall foliage. Of course, shots of cooler air are still inevitable, and as we head towards November we expect a return to a typical late fall pattern with classic fall storms and a few reminders that winter is just around the corner.

While western Canada will take a break from being the warmest part of the country, above normal temperatures will still dominate the season for most of B.C. (closer to normal for the south coast), as well as across most of the Prairies and much of northern Canada.

The southern Maritimes and southern Newfoundland should also see above normal temperatures this fall, thanks in part to warm water temperatures in the western Atlantic basin. In between, from eastern Manitoba to Labrador, and north to Baffin Island, temperatures are expected to be near normal for the season.

What is Normal?

Fall is a transition season in which "normal" is a constantly moving target. Most cities across Canada lose 1 to 3 degrees from their average temperature each week throughout the fall season.

Using the example of Toronto below, you can see that the months of September, October, and November are when we see some of the largest temperature changes throughout a typical year. This inevitable trend underlies the pattern this year as always. 

Precipitation Patterns

While the upcoming months are famous for their classic fall storms, the first half of fall is expected to be less active than normal across most of the country. However, a more typical pattern is expected late in the season. 

After a period of wetter weather early in the season, much of the southern Prairies may trend back into the dry pattern we saw through much of the spring and summer. The West Coast however, including Victoria and Vancouver, should see enough Pacific moisture to keep rainfall totals near normal, bringing some relief from the dry summer.

The Great Lakes region to southern Quebec will see a break from the active pattern that dominated the spring and summer season. Extended periods of warm and dry weather are likely, but totals for the season are expected to be near normal due to an increase in active weather later in the season with the potential for a couple systems to tap into subtropical moisture and bring heavy rainfall.

Atlantic Canada can expect near to slightly above normal precipitation this fall, thanks in part to lingering warm water in the western Atlantic and the threat for excessive rainfall from any systems coming out of the tropics, as the active Atlantic hurricane season stretches well into the fall.

Autumn in full swing at Montmorency Falls, Que. says Keith Robitaille, who took this image on Oct. 16, 2017 Canadians share their best fall photos

Readers share their fall photos (Weather Network)

Winter Preview

Looking even further ahead, here is our current thinking on how the pattern will look as we head into winter. Given some strong similarities in the global weather patterns, we expect the overall pattern this winter will resemble the winter of 2016-2017, but with some important differences.

We don't expect this winter will be as persistent or severe as it was last year along and near the south coast of British Columbia, which should mean less snow for the Lower Mainland. The BC mountains are not expected to match last year's epic snow totals either, but there should still be more than enough accumulation for a strong ski season.

An active storm track is expected to bring more Colorado Low type systems into the Great Lakes, which should mean more system snow and mixed precipitation for the region. An active storm track is also expected into Atlantic Canada with near normal temperatures.

The coldest air relative to normal is expected to settle into the middle of the country this winter, bringing below normal temps from the central Prairies through the western Great Lakes.

We will continue to monitor global patterns and refine this forecast as the fall season progresses. We will have much more detail on what to expect this winter in our next seasonal outlook, which will be released at the end of November.

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