A drenching start to March has roads crews scrambling around the Puget Sound area, with mudslides and rushing water closing nearly 20 King County roads, and more closures possible.

“The ground is so saturated there’s no good way to tell when these roads will be reopened … and more rain is expected to move in,” said Rochelle Ogershok, county transportation spokeswoman.

At least two Western Washington rivers, the Skokomish in Mason County and the Snoqualmie in East King County, had spilled over their banks by early Thursday.

Although rainfall eased through the day Thursday, the chance of saturated soil triggering mudslides remains a possibility through the weekend, said National Weather Service hydrologist Brent Bower.

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By midday Thursday, less than a full week into March, Seattle-Tacoma International Airport already had recorded more March rain — 3.83 inches — than it normally gets for the entire month — 3.72 inches.

And that comes on the heels of a wet February,

when the airport had 6.11 inches of rain, compared to the normal 3.5 inches.

More than half this week’s rain fell Wednesday. Its 1.84 inches of rain made it the wettest day at SeaTac since Nov. 19, 2012, which had 2.13 inches.

Among the affected roads in King County was Vashon Island’s Dockton Road, on the narrow strip of land connecting Vashon and Maury islands. The road was covered by a mudslide about 8:30 p.m. Wednesday. Ogershok said crews hoped to reopen the road by late Thursday.

Elsewhere around Western Washington, a mudslide shortly after noon Thursday blocked the westbound lanes of Highway 20 east of Concrete. State Patrol troopers conducted drivers through the area by alternating traffic on the single open lane. The debris was cleared by 9:30 p.m.

And at Mukilteo, a couple of mudslides onto the BNSF Railway tracks caused Sounder and Amtrak passengers to be bused around the area.

Gus Melonas, spokesman for the BNSF Railway, said freight trains were expected to be able to resume travel on the route late Thursday after the mud, rocks and debris were cleared from the tracks.

But passenger trains will have to observe a 48-hour safety moratorium until Saturday night, Melonas said.

Friday’s forecast is for partly sunny weather, with a 30 percent chance of showers before 10 a.m. and a high near 55 degrees. Rain could be hit-and-miss over the weekend, with the Weather Service forecasting a 50 percent chance of rain Saturday and 80 percent Sunday, with highs for both days in the mid-50s.

Jack Broom: broom@seattletimes.com