The legal authority for the bulk telephone metadata program Edward Snowden disclosed is set to expire at the stroke of midnight on Monday. But there are lesser known Patriot Act surveillance measures also set to sunset at that time unless the Senate acts quickly.

Senate Majority Leader Mitch McConnell, a Republican of Kentucky, has ordered the Senate to session on Sunday in an 11th-hour bid to salvage the Patriot Act. Unless lawmakers approve extending those provisions under the guise of the USA Freedom Act—which has already passed the House—all three surveillance powers will be no more.

President Barack Obama is expected to sign the act if it passes the Senate. And even if it does, the House's measure removes the bulk telephone metadata from the hands of the National Security Agency and lets it rest with the telecoms. The government could still search the metadata with a warrant from a secret court, as long as the nation's spies articulate a reasonable suspicion that the phone data is relevant to a terror investigation. The Fourth Amendment's probable cause standard does not apply to searching the metadata that includes phone numbers of both parties in a call, calling card numbers, the length and time of the calls, and the international mobile subscriber identity (ISMI) number for mobile callers.

Beyond the metadata debate, however, the so-called "lone wolf" and "roving wiretap" provisions reauthorized by the House's USA Freedom Act are also in play.

"I sure hope Congress figures out a way to make sure I don't lose these essential tools," FBI Director James Comey said.

Sen. Lindsay Graham, a Republican of South Carolina, said that "anybody who neuters this program is going to be partially responsible for the next attack."

Jameel Jaffer, the American Civil Liberties Union's legal director, said the legislative debate amounts to "scaremongering."

The "roving wiretap" provision allows the nation's spies to get a warrant from the secret Foreign Intelligence Surveillance Court (FISA Court) without having to identify the target, and it gives the government the authority to tap a suspect's line as he hops from one device to another.

The "lone wolf" provision allows the government to get a warrant from the FISA Court to electronically monitor somebody—and the government does not need to show that the suspect is an agent of a foreign power or linked to terrorism.

A third expiring Patriot Act section—the "business records" provision— is the authority that allows the bulk telephone metadata program. But it goes beyond that. With permission from the FISA Court, it allows the authorities to seize all types of documents, including health and banking records, so long as the authorities assert that they are "relevant" to a terrorism investigation.