At a Glance

We've barely stepped into autumn, but some areas have had a very snowy start.A number of cities from eastern Washington to the Dakotas have had a record-snowy start to the season.This is due to a late September winter storm, then a blizzard last week.

Just three weeks into autumn, a pair of unusually strong early season snowstorms delivered the snowiest start to the season on record to parts of the northern Rockies and Northern Plains.

By season, we mean that time of year between the first snow of fall and last snow of spring.

And so far, it's been a busy start.

A buried parts of the far northern Rockies in up to 4 feet of snow.

, named Winter Storm Aubrey by The Weather Channel, dumped up to 30 inches of snow and brought blizzard conditions to parts of North Dakota.

(MORE: Where October Snow Is Typical)

Record Snowy Cities So Far

Through Oct. 13, six cities in an area from eastern Washington to the Dakotas have had a record-snowy start to their snow season.

Plotted above are the six cities with a record-snowy start to the season through Oct. 13 and their seasonal snowfall totals in inches. The contours are an estimate of seasonal snowfall. The heavier snowfall is shown by the lighter pink contours.

(Data: National Weather Service)

Spokane, Washington, has already picked up 6.9 inches of snow this season, almost five times its previous snowiest start of 1.4 inches in 1926. In an average season, it would take until Nov. 29 for this amount of snow to fall in Washington state's second-largest city.

Spokane had only its second September snowfall on record when it picked up 3.3 inches from Sept. 28 to the 29th. Tree limbs weighed down by wet snow were pushed into power lines by strong winds, triggering power outages in the city.

Just over a week later, another 3.6 inches of snow blanketed the city from Oct. 8-9, leading to more downed trees and power outages.

A whopping 27 inches of snow has already piled up this season in Great Falls, Montana, more than double its previous record-snowiest season-to-date: 13.1 inches in 1957. That's about 43% of its average snow over an entire year (63.1 inches) in just a few weeks. It doesn't pick up that much snow in an average season until Jan. 13.

The northern Montana city was buried by its second-heaviest two-day snowstorm on record, picking up 19.3 inches of snow from Sept. 28-29. Just nine days later, another 7.7 inches of snow blanketed Great Falls.

Bismarck, North Dakota, picked up 17.1 inches of snow from the Aubrey last week, almost tripling its previous record-snowy season to date set 121 years ago (5.8 inches in 1898).

Aubrey was Bismarck's record-earliest in season 1-foot plus snowstorm, and only the second such storm of record in October, joining the infamous Halloween 1991 blizzard.

North Dakota's capital city had four straight days of measurable snow from Oct. 10 to 13, double its average for the entire month.

Fargo, North Dakota, only picked up 4.5 inches of snow last week, but that was double its previous snowiest season-to-date of 2.2 inches in 2006.

(MORE: Snowstorm Is the Last Thing Flood-Weary Plains Needs)

In South Dakota, last week's snowstorm set snowiest-so-early-in-season records in both Aberdeen (5 inches) and Huron (5.5 inches). It was the first 5 inch-plus October snow event in Aberdeen since 1932.

Why Such a Snowy Start?

A jet stream pattern has repeated itself since the last few days of September and produced the aforementioned snowstorms.

More specifically, a pronounced southward plunge of the jet stream, known to meteorologists as a trough, carved itself into the West, then slowly rolled into the Plains. To the east of this trough, moist air lifts to form clouds and precipitation.

The jet stream since the last week of September has taken a sharp southward plunge in the West, with a storm track favoring heavier precipitation, including snow, in parts of the Rockies and Northern Plains.

In the case of both of the snowstorms, air near the ground was just cold enough to support accumulating snow rather than rain.

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