WMOD00277

• Contract/Permit #: 14-06-D-6467
• Title: An Operational Adaptation Program for the Colorado River Basin
• Prepared By: Lewis O. Grant, Chappell, Crow, Mielke Jr., Rasmussen, Shobe, Stockwell, Wykstra
• Date: 10/1/1969
• State: CO
• Country: United States
• Weather Modification - Doc Type: Report

100
en
;;r 90
o
Z80
o
ti 70
~60

@50
0::
0.. 40
"-
030
w
<.92
~
i'5 10
U
~O 102030405060708090100
PERCENTAGE OF TOTAL SNOWFALL

Figure 35. -- Wolf Creek Summit daily distribution of
snowfall, November 1958 - April 1968 (November -
April).

surface through the continuous cloud cover. On the
three days shown in Figure 36, the daily temperature
ranges were 90 , 100 , and 60 , respectively. Since
these temperatures are observed at 11,300 ft during
a time when the vertical temperature distribution,
both in and beneath the cloud should be near the satura-
tion lapse rate, it is quite probable that a daily
variation of up to 100 is taking place in the lower
portion of the cloud.

f. Variability of snow accumulation
The highest total cumulative snow
depth as usually measured by the Soil Conservation
Service occurs in their April 1 reading.

December 25, 1964

24 hr. total
....50

Determination of the variability of the April 1
reading has been made for the different sub-areas
of the Colorado River Basin. !
I
The four snow courses in the Grand
I
Mesa area show the lowest variability. This
indicates that this area not only coftsistently receives
large amounts of snow each year bVt it does so with
regularity. The highest variability occurs in the
snow courses that are on the eastet-n slopes of the
Rocky Mountains and other mounta~nous areas which
are located downwind from higher terrain.

,
g. Summary comments on the surface
clima tology !
The predominant characteristics of
wintertime storms in the Colorado' Rockies can be
summarized as follows: '

Precipitation occurs on nearly half the days,
November through May at elevations above
10,000 ft. !

Most daily precipitation amounts are less than
. 3 inch per day. '

Precipitation occurs at about l;1alf the stations
during about half the hours when precipitation is
occurring over a given region:

Storm periods lasting three o~ more consecutive
days are normally less frequ~nt than one. per
month. '

I
~I

In the San Juan area precipitation usually begins
in the mountain areas, expands upwind to the
lower elevations, and generally ends last at
Ouray on the northern slopes.: This is probably
due to the favorable orographic effect produced
by the northwesterly airflow which exists after
the frontal or trough passage.;

January 29 - 30, 1965

24 hr. total
... .64

24 hr. total
-.45

I
12

I
12

r0<;;1'r0-C\Jr0C\JCOC\J

~
6 12 6
a.m. p.m.

o.m.

a.m.

200 F. -

/24.

, 250
2~ ~
!-----------~- . .

130

IOOF.

Figure 36. --Examples of daily temperature range during
continuous cloud cover and snow at Climax 2NW.

52