Complex Storm Targets Plains,East

UPDATED 5:30 PM MDT, October 2, 2013

UPDATED By WeatherBug Sr. Meteorologists, John Bateman and James West

 

 

 

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A complex autumn storm is setting a target from the Rockies to the East Coast, and between Thursday and next Tuesday, it will produce plenty of unsettled weather. Severe thunderstorms, heavy rain, and even an early-season snowstorm are all in the cards.

Big changes are already taking place to produce the year`s first widespread autumn storm. A strong cold front is just coming together today across the Pacific Northwest. Cold air has been streaming southward from Canada since the start of the week, all in the wake of last weekend`s record-setting Pacific storm.

Advancing into the High Plains, this developing storm will feed off a warm and moderately humid air mass that has been in place across the central U.S. all week. The cold front will serve as the boundary between the colder air to the north and west, and the summer-like air to the south and east. A new area of low pressure will develop in the Colorado Rockies, marching northeastward into the Dakotas on Thursday. This will set off a volatile mix of weather.

The first result of this storm will be heavy snow, which will develop across the higher terrain of Montana, northern Wyoming, and western South Dakota on Thursday. During the course of Thursday, snowfall rates of 1-to-2 inches per hour could lead to significant snowfall along the Interstate 29, 94 and 90 corridors of Montana and Wyoming.

Winter Storm Warning and Watches along with Winter Weather Advisories have been issued for portions of southern Montana, much of eastern Wyoming, southwestern South Dakota, northwestern Nebraska, as well as for locations in Idaho, Oregon, and the Colorado Rockies.

Totals will reach as high as 10 or 20 inches above 6,000 feet in Wyoming, and 6-to-10 inches in the lower elevations. Similar totals are expected in Montana.

The heavy, wet nature of the snow could cause branches and trees to break onto power lines, causing widespread power outages. Winds gusting as high as 35 mph may produce blizzard conditions and treacherous driving. Residents should be prepared with blankets, non-perishable food, and flashlights. Drivers should be prepared for road closures and should make sure that they have chains packed.

In the warm air bubbling south and east of the front, severe thunderstorms are expected to crash the central Plains and Mid-Missouri Valley later Thursday and Friday. The combination of warm and humid air and racing winds aloft could lead to 60-to-70 mph winds, golf ball-to-baseball-sized hail, and even a few tornadoes. Storms on Thursday could impact Omaha, Neb., and Des Moines, Iowa. The slow-moving system could once again target the same areas on Friday, with a line of storms building from Minnesota to Oklahoma.

As if that weren`t enough, another player will be waiting in the wings, ready to become part of the equation this weekend. A tropical disturbance, currently south of Cuba and east of the Yucatan Peninsula, will move into the Gulf of Mexico later this week. Although it won`t bring much other than occasional showers to Florida`s west coast, it will organize as it feeds off the warm waters of the central Gulf this week.

There`s even a chance that this disturbance could develop into the season`s twelfth depression, or even into the next named tropical storm. If that happens, it would be given the name "Karen."

Over the weekend, the weather scenario will get quite complex as the low and its cold front march northeastward through the Mississippi Valley and into the Midwest and South. The tropical system will then be pulled northward across the central Gulf Coast. Gusty winds and thunderstorms could be an issue along the Florida coast on Saturday, but the main risk will be heavy rain that will follow the low through the Southeast Saturday night into Sunday.

Showers and a few thunderstorms will follow the path of the cold front, now draped from the Great Lakes to the Louisiana coast. While the severe threat will likely be gone by Saturday, a few heavy rain-producing boomers are still expected from Detroit to Memphis and Nashville, Tenn., and into New Orleans, as cooler air behind the front clashes with the summer-like air mass ahead of it.

Also gone by the weekend will be the heavy snow threat, although areas of northern Minnesota and Michigan`s Upper Peninsula could see heavy rain change over to a wet snow late Saturday or early Sunday.

By Monday, the tropical disturbance will move into the Mid-Atlantic as it merges with the approaching cold front. This will provide the cold front with an injection of moisture and atmospheric energy. Heavy rain will be likely ahead of the front from Virginia to New England from Monday evening into Tuesday morning.

Check back often with WeatherBug for the latest on this complex weather situation. Be sure to keep WeatherBug active to receive the latest weather in your neighborhood and get the latest updates anywhere on Twitter.