"If after watching the last video you thought you could still get out and travel, well you haven't seen anything yet!" the Facebook post said.
And later, it followed that up with another indication of how bad things were getting.
"Amarillo Airport just recorded a gust of 65knots/75mph! This is truly a historic blizzard!" the second Facebook post said. "Conditions have NOT improved. Please stay inside and do NOT venture out."
As of 4 p.m. (5 p.m. ET), 19 inches of snow had fallen in Amarillo -- an all-time single day record for February, the weather service said. Monday's accumulation also ranked as the second highest single-day snowfall accumulation ever recorded there, the agency said.
For some, the service's warnings didn't come soon enough.
Emergency crews were having trouble reaching drivers who were caught on the roads, Texas Department of Public Safety Trooper Gabriel Medrano said. Cars were in ditches, he said, because drivers couldn't tell where road ended and ditch began.
National Guard units were being sent to help stranded motorists, the Texas DOT said.
CNN iReporter Jason Boyett in Amarillo posted a video showing near-whiteout conditions at 7:40 a.m., and followed that with another showing a drift nearly 3 feet high outside his front door.
"We get high winds and we get big snowstorms, but they're not often combined," Boyett said.
Whiteouts were also reported in Oklahoma, where as of 10 a.m. Central time, the state had closed all highways in six counties -- Ellis, Harper, Woodward, Beaver, Texas and Cimarron -- until further notice.
"Roadways and ditches are snow packed with no visibility and are very slick and hazardous. All travel is discouraged," the Oklahoma Department of Transportation said. As much as 16 inches of snow could fall in western areas of the state, the weather service said.
Oklahoma Lt. Gov. Todd Lamb declared a state of emergency for 56 of Oklahoma's 77 counties.
Visibility was low in Fairview, Oklahoma, midway between the Panhandle and Oklahoma City, said CNN iReporter Brandi Whitacre.
"Right now it is snowing so heavily I can barely see down our driveway, which is 100 yards or so. It is coming down," said Whitacre, who added that'd she'd lost satellite TV service and was experiencing intermittent power outages.
The blizzard is the second major winter storm to hammer the region in a week.
The number of people under blizzard and winter storm warnings, watches and advisories totaled 35 million, according to CNN's weather unit.
Wichita schools were closed for the third straight school day as the new storm roared in on the heels of one that dumped up to 22 inches of snow on some areas late last week.
Kansas' governor on Sunday extended a state of emergency declaration to include the new storm.
Gov. Sam Brownback said Monday that one person had been killed in a single car accident in Sherman County. Officials blamed the fatal wreck on icy roads.
The Kansas Department of Transportation reported that many highways in the central part of the state, including Interstate 70, were completely covered by snow and ice on Monday morning.