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TABLE XIX. --Upper level meteorological parameters associated with excessive daily snowfall on Wolf Creek Pass. Storm events have produced 1. 20 inches water equivalent per 24 hours at Wolf Creek West and/or Wolf Creek Summit. W. C. West W. C. Summit 700 mb 500 mb 700 mb 500 mb 700 mb 700 mb Mean Daily Daily Wind Wind Wind Wind Mixing Equiv. 500 mb Temp. Convective Date Precip. Precip. Direction Direction Speed Speed Ratio Pct. ~ Temp. Advectim Instability (Inches) (Inches) (Degrees) (Degrees) (MPS) (MPS) ~ (OK) (OC) (OC/12 hI) (OC) - (Unseeded 11-25-65 1. 60 M 250 250 19 32 3.93 316.8 -15 O. 2.7 12-23-65 M 2.27 210 220 13 25 4.04 313.9 -18 2.3 1.5 12-30-65 M 2.60 220 230 28 32 3.73 316.2 -15 6:4 2.8 12-16-67 1. 34 1. 24 180 190 13 28 3.73 310.7 -18 2.6 3.9 12-19-67 1. 97 1. 65 220 240 18 28 2.43 304. 8 -22 7.1 3.9 12-20-67 2.11 2.10 220 220 17 28 3.00 306. 4 -21 0 3. 5 1- 28-68 1.43 1. 76 220 230 19 31 2.73 307.9 -21 4.2 1.1 2 -13 - 68 1. 41 .84 240 260 5 15 2.26 298. 8 -23 1.1 8.4 Average 1. 64 1. 78 220 230 16.5 27.4 3.23 309.4 -19.1 2. 9 3. 5 (Seeded) 12-28-64 M 2.40 250 260 18 29 2.84 310.4 -18 3.7 4.6 1-7-65 3.05 2.39 230 230 9 32 3.60 312.6 -13 0 10.4 1-8 -65 1. 52 .98 230 230 17 32 2.99 311. 9 -18 0 1.5 4 -10-65 1.20 .74 220 230 17 23 2.62 309.7 -21 2.8 -1. 0 12 -6 ,.66 2.43 3.03 260 280 22 29 4.42 317.1 -12 8.9 7.4 12 -7 -66 2.40 2.13 240 250 16 27 4.61 318.8 -14 3.1 3.3 3-11-67 1.21 1. 04 240 230 15 23 2.94 309.6 -19 -2.5 3.1 Average 1. 97 1. 84 239 244 16.3 27.9 3.43 312.9 -16.4 2.3 4.2 Overall Average 229 237 16.4 27.7 3.33 311.2 -17.8 2.6 3.8 As might be expected the moisture , content is relatively quite high during these excessive snowfalls. The 700 mb mixing ratio ranges from 2. 26 gm/kgm upward to 4. 61 gm/kgm during these events averaging about 3. 2 gm/kgm for unseeded and 3.4 gm/kgm for seeded cases, respectively. Equivalent potential t.emperatures at 700 mb associated with these storms are also relatively high ranging from 2990 K to 3190 K for individual days. The average varies from 309.40 K for the unseeded events to 312. 90 K for seeded cases. Temperatures near cloud top (500 mb) range from _150 C to _230 C with an average of -19.10 C for the unseeded events. The seeded episodes have 500 mb temperatures ranging from _120 C to _210 C with an average of -16.40 C. These excessive snowfall events gencrally occur with the 700-500 mb layer stab:,e with respect to moist convection. Only the seeded case of April 10, 1965, shows a decrease of equivalent potential temperature through the layer. Table XIX also shows that daily snow- falls of 1. 20 inches water equivalent have occurred on Wolf Creek Pass during every month from November through April during the 1964-68 winter season. However, the month of December had 8 of ! the total of 15 occurrences and the six-week period from November 25 through January 8 accounts for almost three-fourths of all occurrences during the four-year period of study. The annual frequency of these events is about 4 per year. The warmer cloud top temperatures (500 mb) during the seeded events are interesting. The difference of 2. 70 C in the means of the unseeded and seeded cases results in a student's "t" value of 1. 58 with 13 degrees of freedom. Thus, a null hypothesis that the means of the two samples are identical may be rejected at the 7% significance level. This indicates some possibility that more of these large daily storms are occurring at warmer cloud top temperatures during seeded years. Two Day Snowfalls Table XX shows the upper air climatology of two day storms on Wolf Creek Pass which produces 4.0 inches water equivalent at Wolf Creek West and/ or Wolf Creek Summit. The annual frequency of such storms has been about one per year during the four years of study. The strong orographic influence and unusually large moisture quantities characterize these storms. The wind flow is southwesterly with speeds generally 33 to 43 knots at 700 mb and 55 to 65 knots at 500 mb while these storms are in progress. 61