UPDATE 1-El Paso warns of cold weather effect on pipeline

* Roughly 6 percent of U.S. marketed gas still offline

* More cold weather expected in U.S. Southwest

(Adds byline, comment from El Paso, details on amount of
gas production offline)

By Jeanine Prezioso

NEW YORK, Feb 7 (Reuters) - El Paso Corp (EP.N) said on
Monday more cold weather in the U.S. Southwest could interrupt
operations on its Colorado Interstate Gas Co pipeline system if
customers fail to maintain adequate supplies.

The company issued an advisory on Sunday that is effective
through Tuesday as frigid weather is expected to sweep back
into the region beginning that day.

The CIG pipeline system delivers gas from the U.S. Rocky
Mountains and Anadarko Basin (located across the Texas
Panhandle, Oklahoma, western Kansas and southeast Colorado) to
customers in Colorado and Wyoming and indirectly to the U.S.
Midwest, Southwest, California and the Pacific Northwest, it
said on its website.

"We're asking shippers and producers to take into account
that weather conditions may change and forecasts for cold
weather could impact the CIG system in coming days," said
Richard Wheatley, a spokesman for El Paso in Houston.

Frigid weather is expected in Texas and New Mexico again on
Tuesday, said Tom Downs, a meteorologist with Weather 2000 in
New York.

"In West Texas especially it's going to be another shock to
the system, but not as cold as last week," he said. "An Arctic
front is expected sometime tomorrow afternoon into evening."

In the next 48 hours there is a chance New Mexico will see
4 or more inches of snow from Albuquerque southward, Downs
added.

Last Thursday, the governor of New Mexico declared a state
of emergency as gas supplies were cut off to thousands of
residents. [ID:nN03173614].

A substantial amount of natural gas production is still
offline.

Total U.S. marketed gas production was off about 6 percent
on Monday, down from around 9 percent last Friday, said Matt
Marshall, senior energy analyst with Bentek Energy in
Evergreen, Colorado.

That number was estimated lower last week at about 5
percent of U.S. demand.

"One hypothesis is producers see more cold weather coming
and they are thinking why go reset everything when you have
another bout of cold weather coming," said Marshall.

The Anadarko Basin is still off about 450 million cubic
feet a day, Marshall estimated.

The Fort Worth Basin in Texas hasn't seen any improvement,
and is still off at least 700 mmcfd, he added.

(Reporting by Jeanine Prezioso; Editing by Lisa Shumaker)