Charlie Clift, 56, was last seen buying outdoor clothing on Tuesday 30 January in Fort William town centre.
Highland and Islands Police said they were increasingly concerned about Mr Clift's welfare.
Lochaber Insp Andrew Bilton said they were asking hikers to keep an eye out for him.
He said: "Given the lack of contact from Mr Clift and the decline in weather conditions, his family, friends and officers are understandably increasingly concerned for Mr Clift's welfare."

Iain Henderson, Dan Tuohy and Peter Nelson are the latest to join a long-term casualty list which already includes Tommy Bowe and Jared Payne.
Darren Cave is also set to miss the back-to-back games against Toulouse.
"Despite all the injuries, I believe we have the capability to win this weekend," said Ulster skipper Best.
Ireland star Henderson could miss the remainder of this season after tearing a hamstring in Friday's Pro12 win over Edinburgh with Nelson out for the rest of the campaign after suffering a dislocated foot in the same game.
Irish international lock Tuohy will be missing for at least two months after fracturing an ankle against Edinburgh while Ireland centre Cave will be out for a couple of weeks because of a shoulder injury.
After the opening Champions Cup home defeat by Saracens, another reverse at Kingspan Stadium would leave Ulster's qualification hopes in trouble but Best is refusing to get too worried.
The Ulster captain is calling for a repeat of the kind of committed display which saw them shock Toulouse at the quarter-final stage of the 1998-99 European Cup.
Best, as a 16-year-old, was in the stands at the old Ravenhill that day and says the occasion was formative in his decision to commit all his energy to forging a professional rugby career.
"You don't remember much about games from when you were that young. You remember two or three standout moments in the game but ultimately what you remember is the atmosphere and being surrounded by screaming people.
"Those are the sort of moments that make your mind up for you that you will do anything you can to be an Ulster rugby player.
"That's what we want to create again on Friday night."
Given Ulster's injury crisis and comparatively slow start to the season, Best has acknowledged that there appears to be a sense of pessimism from the club's supporters about the remainder of this season.
"People are very down on us.
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"I've heard people saying that if Ulster lose on Friday night that we are completely gone from Europe but actually that's not the case, because we will have played only two games.
"Bath lost their first two games last year and still went through - although they were the first team to do that."
Best believes Ulster must attempt to impose their game on Toulouse early on rather than adopting a cautious initial strategy.
"We have to pick it up. We can't wait to see what Toulouse are doing.
"We have to show them from the off: 'This is what Ulster Rugby is all about'.
"Yes, we have a couple of injuries but that hasn't affected our build-up. We've got to try to force them to have to cope with us."
Police are searching for a man from south Wales who went missing while hiking in Scotland.
[NEXT_CONCEPT]
Rory Best has urged Ulster not to wallow in their injury woes and instead produce a big performance in Friday's European game against Toulouse.