Avalanche Occurrence and
Weather Conditions Colorado State Highway at Loveland and Berthoud Pass
1961-1962 Season
Winter came early this season with 12 inches to 18 inches of snow in the mountains on Labor Day. The recording instruments (precip-itation, temperature, humidity and barometric pressure) were placed in operation on October 8, and all instruments and gages were
operating by November 1. Skiing was poor to fair from the middle of September to the first of November, and from then on to the fore-part of May, it was excellent. With the early snowfall, early avalanche activity appeared. At Berthoud ski area artificially released slides on November 4, at Seven Sisters the howitzer
brought down slides on December 5, and at "AU Basin on November 24 an· unusual slide caught and killed a University of Colorado student. For the season the total new snowfall, 292 inches for 7 months at the Loveland station, was slightly over normal with January and February being much greater than normal. The maximum depth on the ground was 89 inches occurring on April 8. Temperatures were
unusually low during December and January with a low of -32 0 recorded on January 10. Temperatures for April were much above normal with daily highs above 400
and lows at night well above O. The last recorded avalanches occurred on April 7 in the Seven Sisters area. However, there were many wet slides later in April that did not reach the highway.
Location of instruments at the Loveland station beside the Highway Maintenance garage was as in previous seasons (since 1953) with
f -inch standard rain gage, hygrothermograph on a platform above the station, and automatic rain gage Friez 775B with staff sage located across the road inside the big bend at the foot of the pass. The anemometer was located in the Seven Sisters area as in the past and does not give proper wind velocity nor direction except for the Seven Sisters slides. To make maximum use of it and its records, it should be moved to the top of the ridge. All instruments operated well except the clock for the rain gage which had to be replaced. Mr. Williamson faithfUlly kept good daily records, and Mr. Lee Watkins plotted weekly these data so that maintenance personnel could see various changes and anticipate changes in weather and road conditions.
The percent of avalanches released by the howitzer was
41
percent less than average which is44
percent. There was a very good reason for this which was not entirely the fault of the maintenance people who, in general, were very watchful and alert for avalancbedanger. The stom starting December 16 continued' to December 22 which was Friday. While intermittent, it did lay down over 12 inches of new snow and cause three slides on,Loveland Pass the morning ofDecember 22. The highway crew was busy cleaning up these slides and, of c'ourse, they did not shoot on Saturday or Sunday,
December 23 and 24, when there is heavy traffic by skiers. December 25 was Christmas so they did not shoot until December 27 when they
brought down seven slides. These slides waited
5
days because tem-perature was fairly constant and cold. However, they could have beenset off at any moment by any of several causes.
A rather large storm occurred December
28
to December31,
laying down 25 inches of snow. One small slide occurred on the west side' of Loveland Pass the morning of December31
which was the clue that the avalanche hazzard was high. Highway crews were busy clearing the roads January 1, and besides it was New Years, and skiers were having their Christmas holiday making traffic heavy. However,another big storm began on January 3 with over 30 inches of new snow. At 4 a.m. January 6, Five Car Slide ran, and before midnight that day, ran again. On January 7 everything let go. The pass was
essentially closed for 36 hours by a total of
16
slides which account for half the slides for the season. This one mistake ruined a whole season's record. Looking back it is easy to see that shooting on January land 2 would have made a lot of difference in percent of avalanches released artificially and might have kept the pass open. However, with this heavy storm, visibility was very poor and plows could not quite keep up with snowfall so that for the safety ofthe public perhaps the pass was just as well closed.
With the exception of these two storms, avalanche control was better
than normal. There were some slides occurring on Saturday and Sunday, the first and second weekends in April, that would have been prevented had the storms occurred during the week~ The policy of not shooting on weekends or holidays because of heavy traffic should be studied. This together with not being able to shoot during a storm reduces the effectiveness of the aval~che program and will in time cause a fatal accident.
Since the fall of
