WASHINGTON - Buckle up. It's going to be a newsy Friday.

The end of the week is typically used by officials and agencies as a dumping ground for major news, but today is shaping up to be big. Really big.

There are expected updates in the Russia investigation. Former FBI Director James Comey is testifying before Congress. President Donald Trump is expected to announce a new pick for ambassador to the United Nations.

The updates in the Russia investigation include prosecutors explaining why a plea agreement with Paul Manafort, Trump's former campaign chairman, fell apart, and a sentencing memorandum that could outline what Michael Cohen, the president's former attorney, told investigators.

Here's everything you need to know about what's sure to be a crazy day in the nation's capital.

What did Manafort lie about?

It was a quick breakup between Paul Manafort, the president's former campaign chairman, and Mueller's investigators.

After months of attempting to fend off charges posed by Mueller's team, Manafort was found guilty of eight criminal counts in August in a bank fraud conspiracy.

Manafort, 69, now facing what could be a life sentence in prison, decided to change gears and reached a plea agreement with Mueller's team, offering to cooperate instead of moving forward with a second trial in the District of Columbia.

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In the plea, Manafort admitted leading a long-running conspiracy involving his work on behalf of a pro-Russian faction in Ukraine led by the country's former president Viktor Yanukovych. He pleaded guilty to obstructing Mueller's investigation.

But that cooperation was short lived.

Story continues

Last week, Mueller's team accused Manafort of repeatedly lying to federal authorities and alleged the plea agreement had been violated. But, the public court filing included no details of what Manafort allegedly lied about.

Today, that is scheduled to be revealed.

Prosecutors in Washington are scheduled to explain what led to the collapse of the cooperation agreement and are likely to outline the alleged lies. The filing could include new details in the investigation and what topics Mueller's team hoped Manafort would be helpful on.

Michael Cohen's cooperation with feds

The man who once boasted that he would take a bullet for Trump is now one of the many who have flipped - and on Friday we are likely to see the extent of Michael Cohen's cooperation with federal agents.

Cohen pleaded guilty in August to campaign finance violations and financial crimes in New York. He also last week reached a separate deal with Mueller's team in which he pleaded guilty to lying to Congress about plans for a Trump Tower project in Moscow, admitting those plans continued well into the 2016 campaign.

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He is scheduled to be sentenced next week but ahead of that, Mueller's team will file on Friday a sentencing memo that will outline what they believe to be a fair sentence for Cohen in light of his cooperation.

The document is likely to shed details about what Cohen has shared, both in the Russia case and in New York where he admitted to paying money to women who alleged affairs with Trump in hopes of keeping them quiet.

A similar document was released earlier this week in the case against Michael Flynn, the president's former national security adviser. The document outlined Flynn's "substantial assistance" in three investigations and that he'd sat down with investigators on 19 occasions.

Comey testifying, new UN ambassador

On top of everything else, the former FBI Director James Comey is scheduled to testify before Congress and the president is planning to announce his new pick for ambassador to the United Nations.

Comey is scheduled to testify before the House Judiciary Committee and the House Committee on Oversight and Government Reform. Republican members of the committees issued a subpoena for him to appear before the new Democratic-led House takes over in January.

More: Donald Trump to name Heather Nauert as next UN ambassador

Members hope to question Comey about his role in the Russia investigation and the decision not to prosecute Hillary Clinton for her use of a private email server.

The president, meanwhile, is planning to make an announcement on who will replace Nikki Haley as ambassador to the United Nations. Two Trump administration officials told USA TODAY Friday evening that Heather Nauert, a former Fox News anchor and the current State Department spokeswoman, would be tapped for the post.

It's unclear how the president will make the announcement.

This article originally appeared on USA TODAY: Mueller, Cohen, Manafort: This is why Friday is expected to be filled with political news