The forecast includes a chance of rain, but that won’t deter the 30,000 runners who will line up on Constitution Avenue and run across the National Mall and through D.C. neighborhoods along the way to finishing 13.1 miles or 26.2 miles.

Washington’s National Marathon is back, rebranded as a Rock ‘n’ Roll USA Marathon and scheduled for Saturday. It touts itself as the only marathon run exclusively in Washington, D.C. (Purists will note that the Marine Corps Marathon starts and finishes in Virginia.)

In general, marathon running is a trend on the upswing, growing alongside urban road racing across the country, and the District’s racing scene is no exception.

This year, runners can expect some course modifications, a steep new hill to climb and some quiet time by the Anacostia River during the second half.

New Course

In 2013, runners will experience a brand new start line and a more scenic course. “We believe the new start line’s close proximity to center city hotels and more than five Metro stops within one mile will ensure the best possible experience for both the city and our race participants,” said Adam Zocks, vice president at Competitor Group Inc. and the director of this year’s race.

According to information provided by CGI, the half- and full marathons start simultaneously on Constitution Avenue at 14th Street. The new route heads westbound on Constitution Avenue with views of the White House on the right and the Washington Monument on the left. The route makes a left on Virginia Avenue near George Washington University, looping back toward the National Mall and the Lincoln Memorial. The course then crosses the Arlington Memorial Bridge and immediately loops back to head back to the Rock Creek and Potomac parkways.

Both full- and half-marathon runners share the same course for the first 12.2 miles before the half-marathoners split and head to the finish line at RFK Stadium. The full marathoners turn toward the Capitol for the second half, which includes a run around Fort McNair to Nationals Park and more than 3 miles along the Anacostia River. As in previous years, RFK Stadium will host the finish line festival and post-race concert.

New Hills

Runners who initially thought the new course had fewer hills are in for a surprise. The new route eliminates the Connecticut Avenue climb between Dupont Circle and Adams Morgan, but it adds the “Calvert Hill,” the steep slope that connects Rock Creek Park to the Woodley Park neighborhood. The Calvert Hill is a 71-foot elevation gain, according to estimates on Strava, a running website, and a 9.6 percent grade. By contrast, the infamous “Heartbreak Hill” at the Boston Marathon’s mile 20 measures a 4.3 percent grade (though Heartbreak Hill is an 80-foot elevation gain over .4 mile, as compared with the Calvert Hill’s .1 mile).

“It’s really not that horrible,” said Brian Danza, president of DC Road Runners, an organization that has helped train runners for the event. “I would much rather run up that hill than slog my way up 18th, Connecticut and Columbia.”

New Owners

D.C. wasn’t always the road-racing-crazed town that it is now. In 2006, the Greater Washington Sports Alliance started the first D.C. National Marathon, with fewer than 700 finishers (no data is available on how many may have dropped out along the way). As the marathon grew in popularity, so did the corporate interest, and SunTrust bank became the official sponsor in 2008.

But by 2011, the race had gotten crowded and chaotic. Runners complained about the lack of mile markers and course time clocks throughout the event and disorganization at the starting line.

Also, Washington’s cash-strapped Metro could not adjust its Saturday schedule for the race. Without an early Metro train, many runners who relied on public transportation came late to the start.

In July 2011, CGI, a global media and event entertainment company, swooped in to acquire the SunTrust National Marathon. It was rebranded as SunTrust Rock ‘n’ Roll USA under CGI’s flagship Rock ‘n’ Roll Marathon Series.

With the new leadership came better organization. Mile markers returned to each post, as well as course clocks around the route. Metro has announced it will open at 5 a.m. to accommodate runners. The corrals in 2012 were more organized than in 2011, according to several race-goers who ran both years. CGI has increased capacity and turnout. In 2011, runner capacity was 15,000, nearly half of what Rock ‘n’ Roll expects for 2013 at the sold-out event.

“We take pride in providing a well-organized event that focuses on the runner experience from start to finish,” Zocks said. “The start line will have 33 corrals segmented by anticipated finish times (wave start), and there will be clear mile marks, kilometer marks and other necessary signage on the course.”

“Competitor Group has fairly deep pockets, tons of logistical experience, pre-negotiated sponsorship deals, and name brand recognition. All of these things bring a level of professionalism to the event that was hard to achieve by a nonprofit organization. All of these things have largely changed the race for the better, giving all runners a more uniform experience, with all the amenities they have come to expect,” Danza said.

“I am, however, weary of organizations that cater to people who have not adequately trained to run a marathon. It is a serious endeavor, and should not be treated as a life ‘check-box’,” Danza added.

“Check-box” or not, a marathon is an impressive run and inspiring to watch. Race-running and race-watching tips are included here.