ST. LOUIS (AP) — A release of water from the Missouri River and recent snow and rain are offering some relief for the Mississippi River.

Though still dangerously low, the Mississippi River channel at St. Louis was roughly 12 feet deep on Thursday — up about a foot-and-a-half since Monday.

River interests are paying close attention because if the channel gets to 9 feet, further restrictions are expected for barge traffic. Experts say the potential impact on shipments of essentials such as corn, grain, coal and petroleum could reach into the billions of dollars.

Forecasters had initially expected the river to get to the 9-foot level late this month. But National Weather Service hydrologist Mark Fuchs said the new forecast shows that won't likely happen until the second week of January.

The season's first major snowstorm dumped nearly a foot of snow in parts of Iowa and nearly 9 inches in parts of Nebraska. Some of that precipitation will eventually flow into the Missouri River. Heavy snow was falling or expected in states along the upper Mississippi River, too, and parts of Missouri got a half-inch of precipitation through rain and/or snow.

"It helps, definitely," Fuchs said. "We're getting a good bit of runoff from this last event and it's going to be a while before the (Mississippi) river goes back down, well into the new year."

The storm was not likely to provide as much benefit to farmers and ranchers stung by the drought that still stretches across three-fifths of the continental U.S. It takes a foot or more of snow to equal an inch of water, so several storms of that magnitude would be needed to make a difference, said Brian Fuchs, a climatologist at the National Drought Mitigation Center.

The U.S. Drought Monitor said roughly 62 percent of the continental U.S. remained in some form of drought as of Tuesday, a portion largely unchanged since July. Nearly 22 percent of the lower 48 states are in extreme or exceptional drought, the two worst categories.

Winter is usually a low-water period for the rivers, but the drought has made for an alarming situation on the Mississippi, especially in the 180-mile stretch from St. Louis to Cairo, Ill. To try and keep barges moving, the Army Corps of Engineers has hired contractors to remove six miles of rock pinnacles near Thebes, Ill. — rocks that can scrape the bottoms of barges in periods of low water.

Mike Petersen of the corps said this week's precipitation is far from a cure-all but does buy time in the rock-removal effort, a process that began this week and is expected to take 30-45 days.

"Any rain we get is a bonus," Petersen said.

Ann McCulloch of the barge industry trade group American Waterways Operators agreed but said concerns remain grave because when the river dips to the 9-foot level, the Coast Guard is likely to limit drafts — the amount of the barge that is submerged — even further. Restricted drafts mean less cargo per barge. McCulloch said that if drafts are restricted to 8 feet or lower, many operators will halt shipping.

"That is why we keep going back to the need for a very small amount of flows from the Missouri River," McCulloch said.

Last month, the corps cut the flow from its Gavins Point dam in South Dakota to 12,000 cubic feet per second from 36,500 cubic feet per second to offset drought conditions on the upper Missouri River. The reduced amount of Missouri River water caused a drop on the Mississippi.

This week, the corps restored 4,000 cubic feet per second — not because of Mississippi River concerns but to help prevent ice formation on the lower Missouri River.

It isn't as much as Mississippi River interests want but Fuchs said it should add about a foot of depth to the Mississippi starting next week.

Ice is a concern on the Mississippi as well with colder weather approaching. Significant ice would further reduce water flow into the middle Mississippi River.

"When the river does freeze up it can go down a couple of feet pretty quickly," Mark Fuchs said.