The Washington State Department of Transportation will close Stevens Pass at 9 a.m. Monday for “extensive avalanche control,” the agency announced on its website Sunday. WSDOT’s avalanche control team aren’t sure how long it will take, but the agency plans to provide an update at 1 p.m.

“We expect to drop a lot of snow and will need a longer than normal closure,” a tweet on WSDOT East’s account said.

An “extended” closure may become necessary, WSDOT’s website said — potentially all day, according to Lauren Loebsack, a spokesperson for WSDOT.

“There is a persistent weak layer where there had been a rain and a freeze in January… under a bunch of new snow in February,” Loebsack said. “It could be an all-day thing.”

Stevens Pass and several other high mountain roads were closed last weekend as well over avalanche danger as heavy mountain snow has piled up.