This was tradegy of mountaineers (not BC skiers).
I post the record cos the location is near to Naeba/Kagura, Niigata.

http://www.mainichi-msn.co.jp/shakai/jiken/news/20060322k0000m040066000c.html

Two women(54 and 62) were killed by hypothemia at Sennokura-yama(2,026m),
Niigata on 2006 Mar 20. The party had another four men(60, 63, 63, and 58)
and two women(56 and 60), who were rescured without injuries.
They started climing on Mar 18, and approached to top of Sennokura-yama at
around noon on Mar 19. (I guess they stayed at tents on Mar 18 night.)
It was windy and snowy. Then, the party realized two women were missing,
started to search them, but did not. They spent for the night at tents there,
and found the bodies apart from 50 meters on March 20 morning. One was
in her sleeping bug. Heli resucued them on Mar 21 morning.

Map:(The center is Sen-no-kura-yama.)
http://map.yahoo.co.jp/pl?nl=36.48.51.52...1%d2%bb%b3&sc=5

Comment:
In Tanigawa range, Sennokura-yama is not a difficult one in summer. Many people enjoy round treckigns from Motohashi to Tairapyo-san to Sennokura-yama in summer. Also, a round trip from Motohashi to Tairapyo-san is a popular BC ski route. There is no trees around the top of Tairapyo-san, and the ridge to Sennokura-yama. I've enjoyed comfortable BC skiing among tree lines of Tairapyo-san in March, but never been to Sennokura-yama which has all icy & frozen.

Miroku-Yama-no-Kai posted the 1st report on their home page.
http://homepage2.nifty.com/mirokuyamanokai/06-3sounanziko-2.htm

My comment had a guess wrongly, sorry.

The report says;
Their planned route was from Tsuchitaru to Sennokura-yama to Mantaro-yama retuning to Tsuchitaru.
On Mar 18, they started Tsuchitaru at 10:30 and tented on a north ridge of Sennokura-yama at 14:00. A little snow and weak wind at that night.
On Mar 19, it was cloudy and weak wind when leaving the tent at 06:45. The destination was a north ridge of Mantaro-yama thru Sennokura-yama. It got strong wind and thick fog from 11:50 on the way to Sennokura-yama. They used a GPS sometimes. Then they realized two women were missing on 1,750m point before reaching the top of Sennokura-yama (2,026m). The time was 12:30. They began seaching, but did not find them, and decided to camp there at that night. The wind was so strong to break tent poles.
On Mar 20, they found a body at 7:30 around 100m above their camping site after one hour and half search works.

My comment:
This route is a "harder" one for mountainers. (This is not for BC skiers.) I guess it would be very tough of March 19 plan. They had to make the plan cos the route has less(no?) trees covered by icy snow. So far, I am very surprised these two experienced mountaineers lost their lives at the situation reported.