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August 27

• 5 a.m.: Katrina is upgraded to a Category 3, or major hurricane, with the Gulf Coast in its path.

• During the day, residents of Louisiana's low-lying areas are told they must evacuate; residents in other low-lying areas are urgently advised to do so. President Bush declares a state of emergency in Louisiana.

• Highways leading out of New Orleans are filled with bumper-to-bumper traffic. Several major interstates are converted to one-way routes away from the city.

• 11 p.m.: The National Hurricane Center issues a hurricane warning from Morgan City, Louisiana, to the Alabama-Florida border, an area that includes New Orleans. A warning means that hurricane conditions are expected within the warning area within the next 24 hours.