ニセコなだれ情報 第74号 Niseko Avalanche Info No.74

Date:
February, 17th 2019

山麓6時-6度降雪なし、モイワ800m-7.8度南南西7.13m/s降雪なし、アンヌプリ1120m積雪深250cm1100m-10.8度西南西7.50m/s、ヒラフ1000m-10.5度北東3.50m/s、水野の沢-9.36度24時間降雪0西6.1-10.8m/s、アメダス倶知安-2.5度24時間降雪0積雪深180cm、日本海弁慶岬北西14m/s、神威岬西南西10m/s気圧1006hPa波高2.1m、

 

気象データに基づく雪崩予測は長く専門家により否定されてきたがニセコでは事故防止の観点から降雪推移による危険予測を行っている。面発生表層雪崩は弱層から起こり弱層は多くの場合温度勾配によって出来る。しかし寒暖差の小さいニセコでは弱層からの危険判定が難しい。事故は悪天候時に多い。山に入る人が吹雪で発達するふきだまりの危険に目を向け、風雪時と直後に風下の谷に安易に入らなければ事故は減らせる。

 

観察から昨日昼前後の暖気流入による弱い霜系の層2月16日層が確認できるが、降雪が少ないため全体の雪崩リスクは低い。各ゲートは朝から開けられる。パトロールの意見を聞きコース外へ出ること。春の滝など立ち入り禁止区域では太陽反射による雪のスラブ化が進み深部層からの雪崩の危険が高まる。ここは同じ向きの水野の沢と違いコントロールが行われていない。入ってはならない。朝のうち少し風が上がる。良い一日を。

 

Mountain base 6am: no snowfall. Moiwa800m: -7.8, SSW7.13m/s, no snowfall. Annupuri1120m: 250cm snow depth, -10.8, WSW7.5m/s. Hirafu 1000m: -10.5, NE3.5m/s. Mizuno no Sawa: -9.36, 0cm snowfall, W6.1-10.8m/s. Kutchan weather station: -2.5, 0cm snowfall, 180cm snow depth. Benkei cape: NW14m/s, Kamui cape WSW10m/s, 1006hPa, 2.1m waves.

 

Although scientists have denied weather based avalanche forecast for a long time, the forecast in Niseko emphasizes mainly in accidents prevention, not the mechanical aspects of avalanche occurrences and have been observing the weather transition as the main hazard evaluation. Surface slab avalanches slides from weak layers, and those weak layers forms mainly due to large temperature clines. The temperature change in Niseko during winter is small and weak layer evaluation is difficult. Most accidents occur during bad weather. If people venturing into the mountains pay attention to the danger of the snowdrifts development during storms, and avoid being in leeward slopes/valleys during and just after storms, then many of the accidents could be avoided.

 

A thin hoar layer (Feb 16th) formed due to yesterday noon warm air-flow, however the general avalanche risk is low as no new snow has fallen on top of it. All gates are scheduled to open from the morning. Listen to the ski patrol’s instructions before going out of the gates. Sun affected slabs are forming in south facing strictly off-limits Haru no Taki area and avalanches hazard from deeper weak layers should be considered. There is no avalanche control done in Haru no Taki. The wind is forecasted to pick up in the morning. Have a good day.



For more information visit Niseko Avalanche Information.

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