With the low snowpack in the mountains this year, they are beginning the clearing process a couple of weeks early and it shouldn't take as long as there isn't as much snow to remove.
Clearing begins next week ostensibly on March 16th. Usually takes over a month to clear but it should take less.
Here's a portion of the WSDOT draft press release...Low snowpack could see the scenic roadway open in less than a month
TWISP – The effort to reopen the North Cascades Highway will begin Monday, March 16 from the east side and work from the west side will start on Mar. 23. Stabilization work on a rock slope west of Rainy Pass is expected to be finished by then, allowing the clearing to begin. Those responsible for the annual reopening effort are optimistic that State Route 20 could be open in four weeks, perhaps even less depending on weather, equipment and personnel.
On Tuesday, March 10, Washington State Department of Transportation avalanche-control specialists and maintenance technicians toured the North Cascades Highway from the Early Winters information center near Mazama to Washington and Rainy Passes via snow cat. Along the way they stopped to measure snow depths at two dozen sites. Snow at the summit of Washington Pass measured only five feet over the highway centerline, about half the depth last year. Snow on the highway below the Liberty Bell avalanche chutes averaged 35 feet deep a year ago but this year the depth at LB1 was 20 feet, LB2 was 15 and LB3, 30 feet deep.
WSDOT closed the highway for the winter last on Nov. 24, 2014. Last year the clearing work started Mar. 31 and the highway opened on May 8.