Tomorrow morning — after a private meeting  tonight with the miners’ families — officials from the U.S. Mine Safety and Health Administration have scheduled a major briefing on their investigation of the Upper Big Branch Mine Disaster.

On the one hand, MSHA is really promoting this event, noting that it is timed to coincide with the one-year anniversary of federal investigators beginning their underground investigation at the Massey Energy mine where 29 workers died.

But MSHA’s latest media advisory also seems to be trying to lower expectations a bit, saying:

MSHA will provide information about the physical evidence gathered in its investigation, as well as summaries of other evidence obtained by investigators. However, the underground investigation, interviews, physical testing and analysis of evidence are still ongoing. As has been the practice throughout MSHA’s investigation, some information will remain confidential in light of a concurrent U.S. Department of Justice criminal investigation, which is also ongoing, and requests by federal prosecutors to MSHA to limit the public release of evidence. President Obama has instructed both agencies to conduct thorough investigations into the tragedy, and to ensure that those responsible are brought to justice.

Interestingly, a pre-trial motions hearing in the case of Massey security director Hughie Elbert Stover had been scheduled for this afternoon in federal court in Beckley. But that hearing was postponed at the request for federal prosecutors, who wanted more time to respond to motions filed by Stover’s defense team — including one motion to toss any statements Stover made to investigators as inadmissible and another to forbid prosecutors from mentioning the mine disaster during trial.

The big question is what new information will MSHA chief Joe Main and his investigative team provide tonight to the families and tomorrow to the rest of us? The report by special investigator Davitt McAteer was pretty exhaustive, and in fact MSHA had already previously agreed with much of what McAteer’s team described in its report.

My understanding is that MSHA isn’t releasing its final report tomorrow. And there’s been no mention that any initial citations will be announced, either. The only hint we’ve gotten about what they’re going to cover is this from Joe Main:

Though our investigation is ongoing, we have been holding briefings throughout the process to keep the public informed and share what we can. MSHA also has pledged to cooperate with the U.S. attorney and the FBI as they bring to justice those who may have broken the law. This public briefing will be a thorough look at what we know so far, while keeping in mind the need to support other ongoing investigations.

It would be informative for the public if MSHA spent some time tomorrow — and perhaps they will — going through the science and physical evidence that they believe discounts the “natural disaster” theory that former Massey board chairman Bobby Inman continues to push (and that Alpha Natural Resources has yet to discount).

What also might be interesting is if MSHA officials spent some time talking about what they’ve found so far during their “internal review” of the agency’s own actions at Upper Big Branch prior to the April 5, 2010, explosion …

One note about the briefing for readers is this:

Interested members of the public unable to attend the briefing will be able to follow MSHA’s presentation online and by telephone. More information on electronic participation will be available on the agency’s website.

UPDATED: To join the live webcast at 10 a.m. Wednesday, click on this link.