Our solid block of great weather crumbles just in time for the weekend, the Capital Weather Gang says. Rain is very likely on Saturday and Sunday, and then only slightly less likely through mid-week.

Besides the weather, travelers should watch out for a variety of traffic and transit obstacles. Annapolis is hosting a triathlon Saturday. The Chesapeake Bay Bridge may see extra traffic because of the NASCAR races in Dover, Del. Be cautious around the 14th Street Bridge work zone if you’re heading for a game at Nationals Park.

And if you’re flying out of Reagan National Airport, check Metro’s weekend maintenance schedule for the Blue and Yellow Lines.

14th Street Bridge

The new work zone continues to create extra congestion on the northbound span of the 14th Street Bridge. Watching the traffic cameras this morning, I saw many vehicles shifting lanes to the right just before they reached the construction island.

There’s no reason to do that. Drivers in the second lane from the left have the option of continuing straight onto 14th Street for destinations in downtown D.C. or bearing right just after the construction island ends and heading onto the Southeast-Southwest Freeway and continue on Interstate 395.

Instead, many drivers are making unnecessary last-moment shifts to the right just before the construction island. So the lane just to the right of the construction island appears to be the most crowded on the bridge. By contrast, there are good-sized gaps in the traffic in the lane just to the left of the construction island. That’s the lane that leads either to 14th Street or the freeway.

Some drivers may be reacting to the big green and white sign hanging across the bridge around where the split begins. If you look at the sign — which is not new — in combination with the road-level sign flashing arrows in two directions to mark the split, your reaction is likely to be that you need to be right of the island to reach the freeway. And that’s not so.

Again: Only the left-most of the four lanes on the bridge is exclusively for 14th Street traffic. All three of the right lanes allow drivers to reach the freeway.

Beltway/Telegraph Road

The Wilson Bridge project plans to close some lanes and shift traffic around the Telegraph Road interchange this weekend to prepare for the new ramp opening from Telegraph Road South to North Kings Highway and for roadway construction.

This work is highly dependent on the weather. Rain could force postponement. Watch for updates.

But if things go according to plan:

The current southbound Telegraph Road lanes will be closed from the Beltway interchange to North Kings Highway, and traffic will be shifted left onto one of the northbound lanes. One lane will remain open each to southbound and northbound Telegraph Road traffic all weekend.

Traffic will not be able to exit from Duke Street onto Telegraph Road South during this time.

Detour for westbound motorists: Continue on Duke Street to Van Dorn South to left on Franconia Road to Telegraph Road.

Detour for eastbound motorists: Continue on Duke Street to Route 1 South to right on North Kings Highway to Telegraph Road.

• The right-hand ramp from Telegraph Road South to Huntington Avenue will be closed during this time. Instead, motorists will use a temporary left-hand turn onto Huntington Avenue, which will be facilitated by police presence.

• Motorists will have full access to turn from Telegraph Road South onto North Kings Highway and East Drive, though East Drive will be reduced to one lane in each direction.

• The Capital Beltway outer loop (I-95/495 North) exit to Telegraph Road South will be closed.

Detour: Motorists should take the Van Dorn South exit to left on Franconia Road to Telegraph Road. Alternately, motorists can use the exit ramp from the outer loop to North Kings Highway toward Route 1 to South Kings Highway to Telegraph Road.

• The ramp from southbound Telegraph Road to the outer loop (I-95/495 North) will be closed.

Detour: Motorists should use the temporary left turn onto Huntington Avenue to Route 1 North to the ramp for the Outer Loop.

• Access to the single southbound Telegraph Road lane will remain open to motorists traveling from Mill Road and from the inner loop (I-95/495 South).

• The ramp from southbound Telegraph Road to the inner loop (I-95/495 South) will remain open for travelers coming from Mill Road.

• Vehicles traveling northbound on Telegraph Road will have all regular access to the Beltway and to local roads.

Metro weekend delays

The transit authority has scheduled a lot of work for all lines except the Green Line this weekend.

Blue/Yellow lines: From 10 p.m. Friday to the midnight closing on Sunday, Blue Line trains will share a track between Stadium-Armory and Addison Road. Workers will be repairing the floating slabs beneath the rails.

From 10 p.m. Friday till the Sunday closing, Blue and Yellow Line trains will share a track between Braddock Road and Pentagon City. Workers will be repairing the aerial structure near the Reagan National Airport Station and installing cellular communications cable.

On Saturday and Sunday, all Blue Line trains will operate about every half hour between Largo Town Center and Franconia-Springfield. All Yellow Line trains will operate about every half-hour between Huntington and Mount Vernon Square.

Red Line: From 9:30 p.m. Friday through Sunday’s closing, trains will share a track between Grosvenor and Twinbrook. Workers will be repairing the platform at White Flint.

Trains also will share a track between New York Avenue and Rhode Island Avenue. Crews are continuing work on the aerial structure outside the Rhode Island Avenue Station.

Throughout the weekend, trains between Shady Grove and Glenmont will operate about every 16 minutes. From 9 a.m. to 9 p.m. Saturday and Sunday, service will be more frequent for riders at the line’s inner stations. Trains should arrive about every six to 10 minutes between Friendship Heights and New York Avenue.

Orange Line: From 10 p.m. Friday through Sunday’s closing, trains will share a track between Ballston and West Falls Church. This will clear space for work related to connecting the new Dulles Metrorail line to the Orange Line and for Metro workers to replace crossties on the Orange Line.

On Saturday and Sunday, every other train in the direction of Vienna will end its run at Ballston, then head back to New Carrollton. Trains will operate about every 12 minutes between New Carrollton and Ballston. Trains between Ballston and Vienna will operate about every 24 minutes.

Constitution Avenue

From 7 a.m. to 5 p.m. Saturday, expect up to two westbound and up to two eastbound lanes to be closed between 23rd and 20th streets. Curb lanes may remain closed for safety.

Annapolis triathlon

Street closures and parking restrictions are scheduled for Saturday in the historic district and West Annapolis in connection with the first TriRock Annapolis Sprint Triathlon.

The start time for the triathlon is 7 a.m. Road closings from the city’s historic district through West Annapolis are scheduled to begin at 6 a.m. The streets will reopen after the last participants pass, and all streets except for the foot of Prince George Street should be open by 10 a.m.

The mayor’s office says that organizers expect that the event will attract 1,500 to 1,800 participants and about 2,000 spectators. The triathlon will begin with a swim in Annapolis harbor, followed by a 12.4-mile bike ride through the historic district along King George Street, looping twice around a section of Route 450 that extends across the Severn River into Anne Arundel County.

The bike ride will end at the foot of City Dock, where a 5K run will begin. That course goes along Main Street, Bladen Street and Rowe Boulevard on the way to the Navy-Marine Corps Memorial Stadium before turning back and finishing at City Dock.

See a map of the route. (pdf)

These are the no-parking zones: The northbound side of King George Street from Randall Street to the King George Street Bridge; the northbound side of Main Street from Compromise Street to Church Circle; Prince George Street from Craig Street to Randall Street. Those restrictions will be in effect from 2 a.m. to 9:30 a.m. Saturday.

Additionally, parking will be restricted on Prince George Street between Annapolis Harbor and Craig Street through 4 p.m. Saturday. City Dock parking lot will be partially closed from 8 a.m. Friday through 2 a.m. Saturday, and then completely closed from 2 a.m through 4 p.m. Saturday.

Beltway bridge

The Maryland State Highway Administration is beginning a two-year rehabilitation project on the Capital Beltway bridge over Northwest Branch between New Hampshire Avenue and University Boulevard in Silver Spring.

Jersey barriers will be installed on both sides of the Beltway. The lanes will shift, and they will be narrowed from 12 to 11 feet. The shoulders will be closed. Single lane closings will be scheduled for 10 p.m. to 5 a.m. weeknights.