Avalanche and weather report for Loveland and Berthoud passes, Colorado state highway, 1963-64 season

I 7

A vakne/uz

ant:!

JI1/,~/jtlr RI~orr

for LeJvt2/O'nd

Qnc:l

Berlho~/d

pg.:SSIS

·

C e;1/e;rodo

Srol-.e

,t/".7Aw~

,

--'

.

Avalanche and Weather Report for Loveland and Berthoud Passes

Colorado State Highway 1963-64 Season

Again the fall was warm and dry after abnormally high rainfall in August and the forepart of September. A small amount of snow the latter part of October quickly melted, .and it was not until the second of November that snow stayed on the ground for the winter at higher elevations and then

there was not sufficient snow (less than 10 inches) for skiing until

mid-December. The storm beginning the day after Christmas brought in a total of 20.5 inches o.f new snow and an avalanche cycle developed December 29-31. It was possible to release seven slides in the Seven Sister area,

artificially with the 75 rom pack howitzer.

A small storm January 17-20, with only 6 inches of snow but high winds much above critical velocity causing much drifting resulted in two naturally released slides, the Professor and No.6 of the Seven Sisters on January 19. Visibility was sufficient so that the morning of January 20, six slides were released artifically in the Seven Sister area and on

January 21, the Stanley Mountain Slide was released with artillery fire. The avalanche cycle was definitely caused by high wind as there was very

little new snow. Below elevation 9500 there was no snow on the ground and old timers said this was the driest winter they had seen.

A series of small snow flurries and high winds caused·a small avalanche cycle February 8-10, No.4 of the Seven Sisters slid naturally in early morning hours and on February 10, the cliffs on the west side of Loveland Pass did the same thing. After daylight came, four slides were released by artillery fire.

Light snowfall of abo~t 3 fnches per 24 hours for 3 days with high wind velocity caused an avalanche cycle beginning with the Black Widow running naturally early in the morning hours of February 19 with medium size volume

causing a 3-hour interruption of traffic. On February 21, after the storm, six slides were released by artillery fire.

A storm beginning March 2, dropped 6 inches of snow·and high winds at the end of the storm on the third d·rifted the snow into the avalanche paths. The dam slide reacted with very small volume and stopped .short of the creek. The evening of March 4, four of the Seven Sisters slid naturally.

The ~orning of the next day No.3 of the Seven Sisters and on March

6,

Stanley and Flora Park were released by artillery fire. Flora Park and Stanley came down in large volume for the first time this winter to the road. This avalanche cycle was caused primarily by high winds.

The storm beginning March 22, lasted for 6 days and was the largest storm of the winter. Nearly 24 inches of snow fell, wind velocities were moder~te, and temperatures were higher. This was a typical spring storm, and it was possible to release all avalanches March 27, by

•

,~

The last avalanche cycle of the season occurred April 13 and 14, and was caused by about 13 inches of snow over 4 days with the highest winds of the winter. Three slides, Flora Park and two of the Seven Sisters ran natural April 13, causing considerable delay in traffic (also visibility was practically zero). On the 14th, seven slides were released artificially. The last slide of the season occurred April 21, as the result of 3-1/2

inches of new snow falling with moderate wind velocity on the 20th. Ten inches of wet snow falling at warm temperatures, the storm of April 26 and 27, did not produce any slides. Except for deep drifts and gullies all the snow had melted by the middle of May which was about one month earlier than normal.

From the avalanche occurrence table it is noted that the total accumulated snowfall for the 6-month season was 193 inches being slightly greater than the 175 inches recorded the prior season. The average for 11 years is 207 inches but this period does contain four very dry years when compared to records extending back to 1926 for other high altitude stations.

Temperatures were below normal for January, February, and March. A total of 56 slides were recorded on Highways 6 and 40 over Berthoud and Loveland passes. This is the larg~number recorded since 1950 when records were started. The average is 36 slides per season. The artificial release of slides results in a greater number but a smaller volume or size of slide. Thirty-five slides of the 56 were classified as small and only 5 as large. The percent of slides released artificially was 73 percent which is the largest for the l4-year period which averages 48.7 percent. Avalanche control was very good. If shooting were done from fixed

positions during prolonged storms and were extended to Saturday and Sunday, the percent of slides released artificially might be increased to 85 to 90 percent. There will always be a few slides that cannot be predicted or released artificially but these should be of small volume and size.

Weather instruments were located at the Loveland Station beside the highway maintenance garage on the east side of the pass. There has been no change

in location since 1953. The 8-inch standard rain gage, hygrothermograph, and snow accumulation stake are on a platform above the station and the Friez 775B rain gage with st'aff gage to measure snow depth on the ground are located across the road ins*de the big curve at the foot of the pass near the Loveland Ski area. All instruments functioned satisfactorily this season.

Mr.

plott~d these data so the maintenance personnel could see the past weather

record and anticipate changes in weather and road conditions. Weather and avalanche records are included in this report and tell the story of this season'sweather and the performance and efficiency of the gun crew headed by Maintenance Superintendent Pat Murray. This crew and superintendent have worked together since the fall of 1957. Their experience in avalanche forecasting and control, together with efficiency and ,firing accuracy

is reflected in the avalanche r~cord.

. ----~

Recommendations

1. Shooting on Friday whenever there is a possibility of any avalanche hazzard has helped to keep the highway open for weekend heavy traffic and should be continued.

2. The Anemometer should be moved to either Straight Creek pass or the ridge above the Seven Sisters to a location selected for it. Records are of very little value. at the present location.

3. Closure of Loveland Pass during extreme stormy periods should be considered. Actually, it becomes closed with stalled cars and trucks creating a traffic block so that snowplows cannot work efficiently. 4. During a bad storm with poor visibility improved means to warn and notify drivers (particularly truck drivers) at Georgetown and Silver Plume would relieve traffic jams and allow snowplows to clear roads. In general, Colorado State Patrol does not seem to take initiative and warn people or patrol passes during such storms •