A powerful winter storm is expected to slam large portions of the country over the next four days, with people from Arkansas to New York potentially in its path.

The National Weather Service on Thursday issued updated watches, warnings and advisories for a storm it’s calling “potentially crippling,” saying it could bring two feet of snow to certain areas.

High winds could also create blizzard conditions in some parts, the service said, and “significant” amounts of ice are expected in Kentucky and North Carolina.

The Weather Channel is referring to the storm as Winter Storm Jonas.

Warnings, watches or advisories had been issued for portions of 18 states as of Thursday morning, including an expanded blizzard watch that included parts of Pennsylvania, New Jersey, Delaware and New York. Previously, the service had only issued the blizzard watch in areas surrounding Washington and Baltimore.

The updated blizzard watch includes major cities like Philadelphia and New York.

Other watches, warnings and advisories had been issued in portions of Arkansas, Missouri, Illinois, Indiana, Ohio, Pennsylvania, New York, New Jersey, Delaware, Maryland, Virginia, West Virginia, North Carolina, Kentucky, Tennessee, South Carolina, Georgia and Mississippi.

Residents of those states should monitor their local forecasts.

The National Weather Service had previously said the storm could impact the entire I-95 corridor, which also includes Boston, though on Thursday indicated that it did not know exactly how much snow is expected to fall north of New York, which is expecting 8 to 12 inches.

The service is calling for 18 to 24 inches of snow near Washington and Baltimore, while other regions in the storm’s path could see double-digit totals. Wind gusts of up to 55 mph are forecast in blizzard watch areas, which may lead to whiteouts and snarl travel.

The storm should begin dropping snow in eastern Arkansas, Tennessee and Mississippi tonight and continue to travel east before leaving the United States on Sunday, according to the National Weather Service forecast. The service’s office in Memphis warned travel will be “difficult if not impossible” by mid-morning on Friday, as 4 to 6 inches of snow and high winds could create near-blizzard conditions.

Similar forecasts about travel impacts were issued throughout the storm’s path.

The Maryland State Police and Virginia Department of Transportation both encouraged motorists to stay off the roads, according to news releases. West Virginia Governor Earl Ray Tomblin declared a state of preparedness and Virginia Governor Terry McAuliffe declared a state of emergency.

“All Virginians should take the threat of this storm seriously and take necessary precautions now to ensure they are prepared for travel disruptions and possible power outages during a cold weather period,” McAuliffe said in a statement.

The storm follows more winter weather that moved through the southern United States over the past few days. The Virginia State Police tweeted that troopers responded to 767 vehicle crashes on Wednesday alone.