The storm dumping heavy rain on the Northwest will take aim at the northern Plains and Upper Midwest, bringing the potential for the first snow of the season.
Waves of downpours will continue to push into the Pacific Northwest through the middle of the week.
After the first wave of rain is scooped up into Canada, the second round will head for the northern Plains on Thursday with cooler air to follow.
The moisture colliding with the cool air will bring the chance for falling snow from the northern Rockies to the Great Lakes.
Cool air from Canada will wrap in behind the developing low across Montana, Wyoming and northern Colorado. Several inches of snow is possible, especially in higher elevations of the northern Rockies.
However, across eastern Nebraska, Iowa and southern Wisconsin, the air will likely be too warm for more than a few wet snowflakes. Gusting winds will also be a factor, with the potential to gusts over 40 mph across the Plains.
By late in the week, the storm has the chance to become more organized over the Plains. If this happens, more snow will fall, even in the Dakotas and northern Minnesota by week's end.
If even an inch of snow falls in northern Minnesota, it would be unusual for the first week in October. The average first measurable snowfall in Duluth, Minn., is not until Oct. 24.
Measurable snow would not be unprecedented, however. The earliest measurable snow for a season in Duluth occurred on Sept. 18, 1991.
Across Colorado, some ski resorts are taking advantage of the cool weather and already making snow. In preparation for the 2013-14 ski season, Loveland Ski Area and Arapahoe Basin Ski Area plan to make snow for as long as conditions allow, according to a press release by Colorado Ski Country USA (CSCUSA).
As AccuWeather.com Staff Writer Jillian MacMath explained when introducing the fall forecast, the shots of cold air across the northern Plains will come later in the season. The warmer air settled over Iowa and Nebraska explains why snow is unlikely across these areas with the upcoming storm.
As AccuWeather.com meteorologists predicted earlier this year, the fall season has started off wet in the Pacific Northwest.
Moisture contributed by Typhoon Pabuk, brought flooding rains to the Northwest this weekend. In addition to wind gusts in excess of 80 mph, parts of Oregon and Washington have been inundated by more than 4 inches of rain.