NOAA's National Weather Service has posted winter storm watches and warnings for parts of the Intermountain West.
Let's start with Echo's impact in the West.
Wintery weather in the United States so far this year:
Snow, winter weather 2015-2016 season across the U.S.
Winter Storm Echo to produce heavy snow in West, Plains, Upper Midwest
LUBBOCK, TEXAS - DECEMBER 27: A highway worker tries to shield himself while walking to his truck on December 27, 2015 in Lubbock, Texas. Coming on the heels of several strong tornadoes, some northern parts of Texas are experiencing blizzard conditions with wind gusts up to 50 mph and as much as 13 inches of snow forecast. (Photo by John Weast/Getty Images)
NEDERLAND, CO - DECEMBER 15: Steve Hauser plows snow in the Caribou Shopping Center in Nederland, Colorado on December 15, 2015. Snow is expected to continue throughout the day. (Photo by Helen H. Richardson/The Denver Post via Getty Images)
NEDERLAND, CO - DECEMBER 15: A yellow lab waits patiently in his owner's snowy old truck along East 1st Street in Nederland, Colorado on December 15, 2015. Snow is expected to continue throughout the day. The dog looked warm and didn't wait long in the car as his owner returned shortly after an errand in the town. (Photo by Helen H. Richardson/The Denver Post via Getty Images)
DENVER, CO - DEC. 15: Anna Renton, 7, right, relaxes while neighbor Graham Langner, 7, has a snow fight with his nanny, Ashely Kish.The Denver metro area received more snow than expected overnight, closing schools across the city with some areas measuring a foot of snow by the early morning. (Photo by Kathryn Scott Osler/The Denver Post via Getty Images)
LAKEWOOD, CO - DECEMBER 15: Crut Liles clears snow from his walkways outside his home in Lakewood, December, 15, 2015. Many schools in the area are closed due to the snow storm. (Photo by RJ Sangosti/The Denver Post via Getty Images)
DENVER, CO - DEC. 15: A CDOT crew runs their plow truck southbound on Colorado Blvd. near E. 13th Ave. in Denver. The Denver metro area received more snow than expected overnight, closing schools across the city with some areas measuring a foot of snow by the early morning. (Photo by Kathryn Scott Osler/The Denver Post via Getty Images)
Al Frelk walks his dog, Shiba, 10, in Lords Park in Elgin, Ill., on Saturday, Nov. 21, 2015. Asked about the snow, Frelk said, 'It's beautiful, but can be tough to drive in. Though Shiba has been waiting 9 months for this.' The first winter storm of the season dropped more than 10 inches of snow at numerous Chicagoland locations. (Stacey Wescott/Chicago Tribune/TNS via Getty Images)
DENVER, CO - NOVEMBER 17: Snow hit the Denver metro area having an impact on air travel at Denver International Airport. They were clearing out from the snow on Tuesday, November 17, 2015. Raul Hernandez shovels snow in the economy lot. Hernandez and his crew had worked all night to clear snow. (Photo by Cyrus McCrimmon/The Denver Post via Getty Images)
LAKEWOOD, CO - NOVEMBER 11: Brandon Nelli, a student at Colorado Christian University in Lakewood, shovels snow during a Veteran's Day snow storm the moved into the area overnight, November, 11, 2015. Lakewood got almost 3 inches in some areas form the storm. (Photo by RJ Sangosti/The Denver Post via Getty Images)
DENVER, CO - NOVEMBER 11: A blanket of white snow covers Fort Logan National Cemetery during a Veteran's Day snow storm the moved into the area overnight, November, 11, 2015. (Photo by RJ Sangosti/The Denver Post via Getty Images)
MONUMENT, CO. - November 17: Bob Swift clearing his driveway of a deep drift of snow in Monument, CO. November 17, 2015 Monument, CO (Photo By Joe Amon/The Denver Post via Getty Images)
An above-average amount of snow covers a small cabin near where the first snow survey of winter conducted by the California Department of Water Resources in Phillips, California December 30, 2015. REUTERS/Fred Greaves
Cameron Shonnard backflips a jump at Squaw Valley in Olympic Valley, California, December 5, 2015. An El Nino is forecasted for California, and regular precipitation has been welcomed after years of drought. REUTERS/Max Whittaker TPX IMAGES OF THE DAY
Fresh snow clings to trees near Big Bend, California, December 4, 2015. An El Nino is forecasted for California, and regular precipitation has been welcomed after years of drought. Picture taken December 4. REUTERS/Max Whittaker
The U.S. Capitol dome can be seen behind piles of snow removed from parking areas and walkways around the Capitol grounds in Washington January 26, 2016. The snowbound Washington area was resuming partial business on Tuesday as trains and buses restarted near-normal service, while federal offices remained closed following a massive blizzard that hammered the U.S. East Coast. REUTERS/Jonathan Ernst TPX IMAGES OF THE DAY
Floodwaters cover Green Avenue after a winter storm in Manasquan, New Jersey, January 24, 2016. A morning high tide surge of 2 feet followed snowfall of about 2 feet in the first major storm of the season. REUTERS/Dominick Reuter
A couple poses for a photo on a snow pile during a snow storm in Times Square in the Manhattan borough of New York, January 23, 2016. REUTERS/Carlo Allegri TPX IMAGES OF THE DAY
WASHINGTON, DISTRICT OF COLUMBIA, UNITED STATES - 2016/02/15: Snow is once again falling across Washington, D.C on Monday, 15 February 2016. The bitter cold was replaced by snow, sleet and rain Monday in the mid-Atlantic states and the South, but many residents were able to hunker down at home with federal offices and many businesses closed for Washington's Birthday. (Photo by Probal Rashid/LightRocket via Getty Images)
A barn painted with the U.S. flag is seen in the snow covered field in Kanawha, Iowa, United States, January 16, 2016. Iowa will be the first state to hold its primary, with both Democratic and Republican events being held February 1, 2016. Picture taken January 16, 2016. REUTERS/Jim Young
Police officers gather outside the Montgomery County Courthouse, where actor and comedian Bill Cosby will arrive for a preliminary hearing on sexual assault charges, in Norristown, Pennsylvania February 2, 2016. Cosby has been charged with the 2004 sexual assault of Andrea Constand, a former women's basketball team manager at Temple University in Philadelphia, Cosby's alma mater. REUTERS/Mark Makela REUTERS/Mark Makela
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Tapping a so-called atmospheric river of moisture from the subtropical central Pacific, this system has already wrung out heavy snow in the Cascades and Siskiyous from western Washington into Oregon, and adjacent low elevations.
As of Sunday morning, 20 inches of new snow had piled up on Oregon's Mount Bachelor Ski Area, and 16 inches of snow had fallen near La Pine, Oregon.
Even elevations as low as 2,000 feet had reported 6 to 8 inches both east and west of Medford, Oregon, early Sunday.
Webcams from both the California and Oregon DOT showed that the snow was impacting travel Sunday morning on Interstate 5 in southern Oregon and northern California. Caltrans closed the northbound lanes of I-5 from Yreka, California, to the Oregon state line for a time Sunday afternoon. Several mountain roads were also closed in southwest Oregon due to heavy snow, falling trees and near-blizzard conditions.
By Sunday afternoon, heavy snow was falling over central parts of the Sierra Nevada range in California. That snow has started tapering off, and winter storm warnings are no longer in effect for the Sierra Nevada.
By Monday, the most significant snow will have shifted into the Rockies, from northern Arizona to Montana, but some snow may linger in parts of Oregon, northern California and Nevada.
Total snowfall should top 1 foot in parts of the northern Rockies.
Significant accumulations are also expected in some lower elevations from the Great Basin to parts of Montana, Wyoming and Utah.
This includes Salt Lake City, which could see its heaviest snowstorm since an unnamed winter storm dumped 13.3 inches on the city January 27-30, 2013. Last season brought the second-lowest seasonal snowfall total on record in the Utah capital, with only 15.4 inches total.
In fact, this Salt Lake Valley snow will likely arrive before Monday morning's rush hour, could fall briefly at the rate of over 1 inch per hour, and may continue to be periodically heavy through the day.
There has also been significant rainfall in southwest Oregon and northwest California's lower elevations, which has triggered some additional flooding. Floodwaters reportedly entered homes Sunday morning near Shady Cove, Oregon, near White City, Oregon, and near Eagle Point, Oregon.
By Tuesday, we expect snow to spread from the northern and central Rockies into parts of the northern and central Plains states.
Tuesday night into Wednesday, low pressure strengthens and heads toward the Upper Midwest, wrapping snow around its circulation in the northern Plains, Upper Mississippi Valley and northern Great Lakes.
Some lingering, wrap-around mainly light snow and wind can be expected in the Upper Midwest and northern Great Lakes Thursday, and even while Echo's low heads up to near Hudson Bay, some lake-effect snow is possible in the Great Lakes into Friday.
As low pressure gains some strength, strong winds Tuesday, Wednesday, and possibly early Thursday may lead to reduced visibility in blowing snow, some drifting snow, and some local whiteout conditions on the High Plains and in the prairies of the northern Plains.
If you have travel plans in these areas, check back for the latest forecast and have an alternate plan ready, including delaying or canceling your trip, as heavy, wind-driven snow can make driving too dangerous.
Check back with us at weather.com for updates to this forecast.
Incidentally, "Echo", from Greek mythology, was a nymph given a speech impediment so she could only repeat what she heard.