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More proof that rain doesn't really melt snowpack
- Amar Andalkar
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14 years 10 months ago #199332
by Amar Andalkar
More proof that rain doesn't really melt snowpack was created by Amar Andalkar
As is obvious based on my previous posts, I love it when data solidly confirms various principles of physics, especially so when those principles are counterintuitive and the results unexpected to most. As in this thread from January 2009 (
30" of snow lost in 21hrs @ Snoqualmie?
), which demonstrated that rain, especially when it falls within a few degrees C of the freezing point, is almost entirely incapable of melting snow.
Looking through the NWAC telemetry this morning, I realized that the rain over the past 3 days has provided an even better demonstation of that fact. This time, unlike in January 2009, the rain fell on a much more consolidated snowpack at Snoqualmie Pass, so the snowdepths barely decreased at all. Over 8" of rain at both Snoqualmie and Alpental, some of it falling at temps above 40 °F, has reduced the snowdepth by not even a few inches.
The first few hours of the storm appear to have produced about 3" of slushy snow, before the switchover to rain early on March 29, then heavy pounding rain most of the day on March 30 and past noon on March 31. Snowdepths at Snoqualmie went from 85" up to 88" and back down to 84" over the last 60 hours, and from 98" to 101" to 98" at Alpental:
[tt]
Northwest Weather and Avalanche Center
and Washington Department of Transportation
Snoqualmie Pass, Washington
3700' temp above Lake Keechelus snow shed
MM/DD Hour Temp Temp Temp RH Wind Wind Wind Hour Total 24 Hr Total Press
PST F F F % Avg Max Dir Prec. Prec. Snow Snow mb
3800' 3700' 3000' 3000' 3800' 3800' 3800' 3000' 3000' 3000' 3000' 3000'
3 28 2200 29 32 33 97 5 10 245 0 .01 0 85 1017
3 28 2300 33 32 32 97 2 9 141 .01 .02 0 85 1016
3 29 0 30 31 32 97 5 8 101 .02 .04 0 85 1016
3 29 100 30 31 32 97 2 6 134 .04 .08 0 85 1016
3 29 200 30 31 32 98 5 9 155 .06 .14 0 85 1016
3 29 300 30 31 32 98 7 10 157 .05 .19 1 84 1015
3 29 400 29 31 31 98 7 10 148 .05 .24 1 86 1015
3 29 500 30 30 31 98 9 12 138 .07 .07 0 87 1014
3 29 600 31 30 31 98 7 12 238 .09 .16 0 87 1015
3 29 700 32 31 32 98 7 17 187 .1 .26 1 87 1015
3 29 800 32 32 34 95 4 9 221 .09 .35 1 88 1015
3 29 900 33 33 34 91 4 12 187 .06 .41 1 88 1016
3 29 1000 34 34 35 93 14 26 257 .05 .46 1 88 1016
3 29 1100 35 35 41 81 14 26 254 .04 .5 1 87 1016
3 29 1200 36 35 41 84 7 19 244 .03 .53 1 87 1016
3 29 1300 34 35 39 91 14 28 301 .02 .55 1 87 1017
3 29 1400 34 35 38 91 12 24 237 .05 .6 1 87 1017
3 29 1500 34 35 39 90 13 21 255 .03 .63 1 87 1017
3 29 1600 34 35 38 89 7 11 236 .02 .65 1 87 1017
3 29 1700 32 34 36 93 5 10 264 .05 .7 1 86 1017
3 29 1800 32 33 34 95 6 11 233 .06 .76 1 87 1017
3 29 1900 32 32 32 96 3 11 237 .06 .82 1 87 1016
3 29 2000 33 33 32 97 5 11 216 .07 .89 1 87 1017
3 29 2100 32 32 32 98 2 6 135 .08 .97 1 87 1017
3 29 2200 32 33 32 98 3 6 129 .09 1.06 1 87 1017
3 29 2300 33 33 32 98 4 8 105 .1 1.16 1 87 1016
3 30 0 35 34 33 98 4 16 275 .18 1.34 1 87 1016
3 30 100 35 35 33 99 8 20 313 .22 1.56 1 87 1017
3 30 200 33 35 33 99 6 15 250 .29 1.85 1 87 1017
3 30 300 36 35 32 99 7 16 269 .45 2.3 1 87 1017
3 30 400 38 37 32 99 11 23 298 .09 2.39 1 87 1017
3 30 500 37 38 34 99 17 29 264 .16 .16 1 86 1017
3 30 600 38 38 35 99 17 32 256 .13 .29 0 85 1017
3 30 700 37 38 35 99 17 26 219 .26 .55 0 86 1018
3 30 800 36 38 35 99 16 29 234 .29 .84 0 87 1018
3 30 900 34 37 35 98 9 20 250 .31 1.15 0 86 1019
3 30 1000 34 35 35 98 8 17 258 .27 1.42 0 87 1020
3 30 1100 34 34 36 98 10 18 247 .22 1.64 0 86 1021
3 30 1200 34 35 35 98 6 14 226 .2 1.84 0 86 1021
3 30 1300 34 35 36 97 5 13 286 .18 2.02 -0 86 1021
3 30 1400 35 36 36 98 4 12 272 .18 2.2 0 86 1021
3 30 1500 35 36 36 97 5 13 274 .14 2.34 0 86 1021
3 30 1600 34 36 36 97 8 15 349 .13 2.47 0 86 1021
3 30 1700 36 37 36 98 3 8 3 .17 2.64 0 86 1021
3 30 1800 38 37 35 98 3 13 246 .09 2.73 0 86 1021
3 30 1900 38 39 35 98 17 31 289 .13 2.86 0 86 1021
3 30 2000 39 39 36 99 11 23 255 .12 2.98 0 86 1021
3 30 2100 39 39 38 99 17 31 239 .17 3.15 -0 86 1021
3 30 2200 39 40 37 99 11 24 247 .08 3.23 0 86 1020
3 30 2300 41 41 37 99 9 17 261 .12 3.35 0 86 1019
3 31 0 41 42 37 99 10 19 244 .11 3.46 0 86 1019
3 31 100 43 43 39 99 14 24 228 .12 3.58 0 86 1018
3 31 200 43 43 41 99 17 45 279 .16 3.74 0 85 1018
3 31 300 42 43 42 96 23 47 332 .14 3.88 -0 85 1017
3 31 400 41 42 42 98 19 32 257 .29 4.17 0 85 1017
3 31 500 41 42 39 98 20 39 231 .25 .25 0 85 1017
3 31 600 39 41 39 98 19 38 289 .32 .57 0 85 1018
3 31 700 38 39 38 98 17 29 236 .25 .82 -0 84 1018
3 31 800 36 38 36 98 11 20 252 .28 1.10 0 84 1019
3 31 900 37 37 35 99 14 37 248 .26 1.36 0 84 1020
3 31 1000 38 36 35 99 18 29 261 .25 1.61 0 85 1021
3 31 1100 37 36 36 98 14 24 247 .17 1.78 0 84 1021
3 31 1200 37 38 37 98 12 24 247 .07 1.85 -0 84 1021
3 31 1300 39 39 39 98 13 22 283 .04 1.89 -0 84 1021
[/tt]
[tt]
Northwest Weather and Avalanche Center
Alpental Ski Area, Washington
Wind sensors unheated and may rime
MM/DD Hour Temp Temp Temp RH RH Wind Wind Wind Hour Total 24Hr Total
PST F F F % % Avg Max Dir. Prec. Prec. Snow Snow
5400' 4300' 3120' 3120' 5400' 5530' 5530' 5530' 3120' 3120' 3120' 3120'
3 28 2200 26 30 33 98 98 11 16 195 0 .03 0 98
3 28 2300 26 30 33 99 98 9 16 190 .01 .04 0 98
3 29 0 26 30 33 99 99 8 15 140 .02 .06 0 98
3 29 100 25 30 33 99 98 10 14 155 .04 .1 0 97
3 29 200 25 30 32 100 99 11 20 175 .04 .14 0 98
3 29 300 26 29 33 100 99 12 31 193 .05 .19 0 99
3 29 400 29 32 100 .04 .23 2 99
3 29 500 26 29 32 100 98 16 33 206 .06 .06 2 100
3 29 600 27 29 32 100 98 18 34 233 .05 .11 2 100
3 29 700 28 29 33 100 98 17 36 232 .06 .17 3 100
3 29 800 29 30 34 97 99 18 37 239 .07 .24 3 101
3 29 900 31 32 34 95 97 18 32 244 .03 .27 3 101
3 29 1000 31 32 36 92 96 14 42 226 .04 .31 3 101
3 29 1100 30 33 38 91 94 14 34 221 .03 .34 3 100
3 29 1200 32 33 38 95 93 16 43 221 .03 .37 2 100
3 29 1300 29 32 37 95 97 2 16 221 .05 .42 2 100
3 29 1400 31 32 38 97 95 0 0 221 .04 .46 2 99
3 29 1500 29 33 38 95 98 0 0 222 .04 .5 2 99
3 29 1600 30 32 38 96 94 0 0 222 .03 .53 2 99
3 29 1700 30 32 35 96 96 0 0 221 .05 .58 2 99
3 29 1800 28 32 33 98 98 0 0 221 .04 .62 2 99
3 29 1900 28 32 33 99 100 0 0 222 .05 .67 1 99
3 29 2000 28 32 33 100 100 0 0 221 .06 .73 2 100
3 29 2100 28 32 33 100 100 0 0 222 .07 .8 2 99
3 29 2200 29 32 33 100 100 0 0 221 .09 .89 2 100
3 29 2300 30 33 33 100 100 0 0 222 .09 .98 2 100
3 30 0 31 33 34 100 100 0 0 222 .11 1.09 2 100
3 30 100 31 33 34 100 100 0 0 221 .19 1.28 2 100
3 30 200 33 33 100 .29 1.57 2 100
3 30 300 33 33 100 .36 1.93 2 100
3 30 400 34 33 100 .14 2.07 2 99
3 30 500 35 34 100 .31 .31 2 100
3 30 600 35 34 100 .24 .55 2 100
3 30 700 35 35 100 .4 .95 2 99
3 30 800 34 34 100 .33 1.28 0 99
3 30 900 33 34 99 .26 1.54 0 100
3 30 1000 33 35 100 .18 1.72 0 99
3 30 1100 31 33 35 99 100 0 0 220 .14 1.86 0 99
3 30 1200 31 33 36 99 100 0 0 222 .15 2.01 0 99
3 30 1300 31 33 36 98 100 0 0 222 .14 2.15 0 99
3 30 1400 31 33 36 99 100 0 0 220 .14 2.29 0 99
3 30 1500 31 33 36 99 100 0 0 221 .14 2.43 0 99
3 30 1600 31 33 35 99 100 0 0 221 .12 2.55 0 99
3 30 1700 31 33 35 99 100 0 0 220 .17 2.72 0 99
3 30 1800 31 34 35 100 100 0 0 222 .09 2.81 0 99
3 30 1900 32 35 36 100 100 0 0 221 .11 2.92 -0 99
3 30 2000 32 36 37 100 100 0 0 223 .13 3.05 0 99
3 30 2100 32 36 36 100 100 16 36 249 .22 3.27 0 99
3 30 2200 34 37 36 100 100 26 48 232 .05 3.32 0 99
3 30 2300 35 36 37 100 100 33 63 235 .06 3.38 -0 99
3 31 0 36 39 38 100 100 35 56 239 .07 3.45 0 99
3 31 100 36 40 40 100 100 35 69 239 .07 3.52 -0 99
3 31 200 37 40 43 100 100 39 77 242 .13 3.65 0 99
3 31 300 36 39 43 96 100 49 89 243 .1 3.75 -0 98
3 31 400 36 39 42 97 100 40 75 243 .24 3.99 -0 98
3 31 500 35 38 41 98 100 41 80 247 .23 .23 -0 99
3 31 600 33 37 39 99 100 32 59 241 .32 .55 -0 98
3 31 700 32 35 37 99 100 34 63 243 .31 .86 -0 98
3 31 800 32 35 35 99 100 25 50 236 .19 1.05 -0 98
3 31 900 32 34 34 100 100 3 29 234 .24 1.29 -0 97
3 31 1000 31 34 34 99 100 0 0 235 .26 1.55 0 98
3 31 1100 32 34 35 100 100 13 55 236 .13 1.68 0 98
3 31 1200 32 35 37 99 100 23 47 239 .03 1.71 0 98
3 31 1300 32 35 38 99 100 24 44 238 .06 1.77 0 98
[/tt]
Hurray, rain does not melt snow!
Looking through the NWAC telemetry this morning, I realized that the rain over the past 3 days has provided an even better demonstation of that fact. This time, unlike in January 2009, the rain fell on a much more consolidated snowpack at Snoqualmie Pass, so the snowdepths barely decreased at all. Over 8" of rain at both Snoqualmie and Alpental, some of it falling at temps above 40 °F, has reduced the snowdepth by not even a few inches.
The first few hours of the storm appear to have produced about 3" of slushy snow, before the switchover to rain early on March 29, then heavy pounding rain most of the day on March 30 and past noon on March 31. Snowdepths at Snoqualmie went from 85" up to 88" and back down to 84" over the last 60 hours, and from 98" to 101" to 98" at Alpental:
[tt]
Northwest Weather and Avalanche Center
and Washington Department of Transportation
Snoqualmie Pass, Washington
3700' temp above Lake Keechelus snow shed
MM/DD Hour Temp Temp Temp RH Wind Wind Wind Hour Total 24 Hr Total Press
PST F F F % Avg Max Dir Prec. Prec. Snow Snow mb
3800' 3700' 3000' 3000' 3800' 3800' 3800' 3000' 3000' 3000' 3000' 3000'
3 28 2200 29 32 33 97 5 10 245 0 .01 0 85 1017
3 28 2300 33 32 32 97 2 9 141 .01 .02 0 85 1016
3 29 0 30 31 32 97 5 8 101 .02 .04 0 85 1016
3 29 100 30 31 32 97 2 6 134 .04 .08 0 85 1016
3 29 200 30 31 32 98 5 9 155 .06 .14 0 85 1016
3 29 300 30 31 32 98 7 10 157 .05 .19 1 84 1015
3 29 400 29 31 31 98 7 10 148 .05 .24 1 86 1015
3 29 500 30 30 31 98 9 12 138 .07 .07 0 87 1014
3 29 600 31 30 31 98 7 12 238 .09 .16 0 87 1015
3 29 700 32 31 32 98 7 17 187 .1 .26 1 87 1015
3 29 800 32 32 34 95 4 9 221 .09 .35 1 88 1015
3 29 900 33 33 34 91 4 12 187 .06 .41 1 88 1016
3 29 1000 34 34 35 93 14 26 257 .05 .46 1 88 1016
3 29 1100 35 35 41 81 14 26 254 .04 .5 1 87 1016
3 29 1200 36 35 41 84 7 19 244 .03 .53 1 87 1016
3 29 1300 34 35 39 91 14 28 301 .02 .55 1 87 1017
3 29 1400 34 35 38 91 12 24 237 .05 .6 1 87 1017
3 29 1500 34 35 39 90 13 21 255 .03 .63 1 87 1017
3 29 1600 34 35 38 89 7 11 236 .02 .65 1 87 1017
3 29 1700 32 34 36 93 5 10 264 .05 .7 1 86 1017
3 29 1800 32 33 34 95 6 11 233 .06 .76 1 87 1017
3 29 1900 32 32 32 96 3 11 237 .06 .82 1 87 1016
3 29 2000 33 33 32 97 5 11 216 .07 .89 1 87 1017
3 29 2100 32 32 32 98 2 6 135 .08 .97 1 87 1017
3 29 2200 32 33 32 98 3 6 129 .09 1.06 1 87 1017
3 29 2300 33 33 32 98 4 8 105 .1 1.16 1 87 1016
3 30 0 35 34 33 98 4 16 275 .18 1.34 1 87 1016
3 30 100 35 35 33 99 8 20 313 .22 1.56 1 87 1017
3 30 200 33 35 33 99 6 15 250 .29 1.85 1 87 1017
3 30 300 36 35 32 99 7 16 269 .45 2.3 1 87 1017
3 30 400 38 37 32 99 11 23 298 .09 2.39 1 87 1017
3 30 500 37 38 34 99 17 29 264 .16 .16 1 86 1017
3 30 600 38 38 35 99 17 32 256 .13 .29 0 85 1017
3 30 700 37 38 35 99 17 26 219 .26 .55 0 86 1018
3 30 800 36 38 35 99 16 29 234 .29 .84 0 87 1018
3 30 900 34 37 35 98 9 20 250 .31 1.15 0 86 1019
3 30 1000 34 35 35 98 8 17 258 .27 1.42 0 87 1020
3 30 1100 34 34 36 98 10 18 247 .22 1.64 0 86 1021
3 30 1200 34 35 35 98 6 14 226 .2 1.84 0 86 1021
3 30 1300 34 35 36 97 5 13 286 .18 2.02 -0 86 1021
3 30 1400 35 36 36 98 4 12 272 .18 2.2 0 86 1021
3 30 1500 35 36 36 97 5 13 274 .14 2.34 0 86 1021
3 30 1600 34 36 36 97 8 15 349 .13 2.47 0 86 1021
3 30 1700 36 37 36 98 3 8 3 .17 2.64 0 86 1021
3 30 1800 38 37 35 98 3 13 246 .09 2.73 0 86 1021
3 30 1900 38 39 35 98 17 31 289 .13 2.86 0 86 1021
3 30 2000 39 39 36 99 11 23 255 .12 2.98 0 86 1021
3 30 2100 39 39 38 99 17 31 239 .17 3.15 -0 86 1021
3 30 2200 39 40 37 99 11 24 247 .08 3.23 0 86 1020
3 30 2300 41 41 37 99 9 17 261 .12 3.35 0 86 1019
3 31 0 41 42 37 99 10 19 244 .11 3.46 0 86 1019
3 31 100 43 43 39 99 14 24 228 .12 3.58 0 86 1018
3 31 200 43 43 41 99 17 45 279 .16 3.74 0 85 1018
3 31 300 42 43 42 96 23 47 332 .14 3.88 -0 85 1017
3 31 400 41 42 42 98 19 32 257 .29 4.17 0 85 1017
3 31 500 41 42 39 98 20 39 231 .25 .25 0 85 1017
3 31 600 39 41 39 98 19 38 289 .32 .57 0 85 1018
3 31 700 38 39 38 98 17 29 236 .25 .82 -0 84 1018
3 31 800 36 38 36 98 11 20 252 .28 1.10 0 84 1019
3 31 900 37 37 35 99 14 37 248 .26 1.36 0 84 1020
3 31 1000 38 36 35 99 18 29 261 .25 1.61 0 85 1021
3 31 1100 37 36 36 98 14 24 247 .17 1.78 0 84 1021
3 31 1200 37 38 37 98 12 24 247 .07 1.85 -0 84 1021
3 31 1300 39 39 39 98 13 22 283 .04 1.89 -0 84 1021
[/tt]
[tt]
Northwest Weather and Avalanche Center
Alpental Ski Area, Washington
Wind sensors unheated and may rime
MM/DD Hour Temp Temp Temp RH RH Wind Wind Wind Hour Total 24Hr Total
PST F F F % % Avg Max Dir. Prec. Prec. Snow Snow
5400' 4300' 3120' 3120' 5400' 5530' 5530' 5530' 3120' 3120' 3120' 3120'
3 28 2200 26 30 33 98 98 11 16 195 0 .03 0 98
3 28 2300 26 30 33 99 98 9 16 190 .01 .04 0 98
3 29 0 26 30 33 99 99 8 15 140 .02 .06 0 98
3 29 100 25 30 33 99 98 10 14 155 .04 .1 0 97
3 29 200 25 30 32 100 99 11 20 175 .04 .14 0 98
3 29 300 26 29 33 100 99 12 31 193 .05 .19 0 99
3 29 400 29 32 100 .04 .23 2 99
3 29 500 26 29 32 100 98 16 33 206 .06 .06 2 100
3 29 600 27 29 32 100 98 18 34 233 .05 .11 2 100
3 29 700 28 29 33 100 98 17 36 232 .06 .17 3 100
3 29 800 29 30 34 97 99 18 37 239 .07 .24 3 101
3 29 900 31 32 34 95 97 18 32 244 .03 .27 3 101
3 29 1000 31 32 36 92 96 14 42 226 .04 .31 3 101
3 29 1100 30 33 38 91 94 14 34 221 .03 .34 3 100
3 29 1200 32 33 38 95 93 16 43 221 .03 .37 2 100
3 29 1300 29 32 37 95 97 2 16 221 .05 .42 2 100
3 29 1400 31 32 38 97 95 0 0 221 .04 .46 2 99
3 29 1500 29 33 38 95 98 0 0 222 .04 .5 2 99
3 29 1600 30 32 38 96 94 0 0 222 .03 .53 2 99
3 29 1700 30 32 35 96 96 0 0 221 .05 .58 2 99
3 29 1800 28 32 33 98 98 0 0 221 .04 .62 2 99
3 29 1900 28 32 33 99 100 0 0 222 .05 .67 1 99
3 29 2000 28 32 33 100 100 0 0 221 .06 .73 2 100
3 29 2100 28 32 33 100 100 0 0 222 .07 .8 2 99
3 29 2200 29 32 33 100 100 0 0 221 .09 .89 2 100
3 29 2300 30 33 33 100 100 0 0 222 .09 .98 2 100
3 30 0 31 33 34 100 100 0 0 222 .11 1.09 2 100
3 30 100 31 33 34 100 100 0 0 221 .19 1.28 2 100
3 30 200 33 33 100 .29 1.57 2 100
3 30 300 33 33 100 .36 1.93 2 100
3 30 400 34 33 100 .14 2.07 2 99
3 30 500 35 34 100 .31 .31 2 100
3 30 600 35 34 100 .24 .55 2 100
3 30 700 35 35 100 .4 .95 2 99
3 30 800 34 34 100 .33 1.28 0 99
3 30 900 33 34 99 .26 1.54 0 100
3 30 1000 33 35 100 .18 1.72 0 99
3 30 1100 31 33 35 99 100 0 0 220 .14 1.86 0 99
3 30 1200 31 33 36 99 100 0 0 222 .15 2.01 0 99
3 30 1300 31 33 36 98 100 0 0 222 .14 2.15 0 99
3 30 1400 31 33 36 99 100 0 0 220 .14 2.29 0 99
3 30 1500 31 33 36 99 100 0 0 221 .14 2.43 0 99
3 30 1600 31 33 35 99 100 0 0 221 .12 2.55 0 99
3 30 1700 31 33 35 99 100 0 0 220 .17 2.72 0 99
3 30 1800 31 34 35 100 100 0 0 222 .09 2.81 0 99
3 30 1900 32 35 36 100 100 0 0 221 .11 2.92 -0 99
3 30 2000 32 36 37 100 100 0 0 223 .13 3.05 0 99
3 30 2100 32 36 36 100 100 16 36 249 .22 3.27 0 99
3 30 2200 34 37 36 100 100 26 48 232 .05 3.32 0 99
3 30 2300 35 36 37 100 100 33 63 235 .06 3.38 -0 99
3 31 0 36 39 38 100 100 35 56 239 .07 3.45 0 99
3 31 100 36 40 40 100 100 35 69 239 .07 3.52 -0 99
3 31 200 37 40 43 100 100 39 77 242 .13 3.65 0 99
3 31 300 36 39 43 96 100 49 89 243 .1 3.75 -0 98
3 31 400 36 39 42 97 100 40 75 243 .24 3.99 -0 98
3 31 500 35 38 41 98 100 41 80 247 .23 .23 -0 99
3 31 600 33 37 39 99 100 32 59 241 .32 .55 -0 98
3 31 700 32 35 37 99 100 34 63 243 .31 .86 -0 98
3 31 800 32 35 35 99 100 25 50 236 .19 1.05 -0 98
3 31 900 32 34 34 100 100 3 29 234 .24 1.29 -0 97
3 31 1000 31 34 34 99 100 0 0 235 .26 1.55 0 98
3 31 1100 32 34 35 100 100 13 55 236 .13 1.68 0 98
3 31 1200 32 35 37 99 100 23 47 239 .03 1.71 0 98
3 31 1300 32 35 38 99 100 24 44 238 .06 1.77 0 98
[/tt]
Hurray, rain does not melt snow!
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- philfort
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14 years 10 months ago #199336
by philfort
Replied by philfort on topic Re: More proof that rain doesn't really melt snowpack
I looked at the Buckinghorse snotel this morning when Gary posted a link to it.
How come it got 14 inches of precip, but almost no increase in SWE?
www.wcc.nrcs.usda.gov/nwcc/sntl-datarpt....1107&days=7&state=wa
How come it got 14 inches of precip, but almost no increase in SWE?
www.wcc.nrcs.usda.gov/nwcc/sntl-datarpt....1107&days=7&state=wa
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- trees4me
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14 years 10 months ago #199341
by trees4me
Replied by trees4me on topic Re: More proof that rain doesn't really melt snowpack
Amar, do you have any material on how rainfall may reorganize/redistribute crystal structure in the snowpack?
Certainly the rainfall is providing some advective energy into the snowpack causing the snow to melt. However the rainfall may not provide enough energy (i'm assuming there's some threshold) where snow crystal structure changes and layers begin to collapse, therefore the snow depth wouldn't be significantly affected.
A very quick search turned up no good articles on how and at what rate rainfall impacts the snowpack crystal/layer structure.
Certainly the rainfall is providing some advective energy into the snowpack causing the snow to melt. However the rainfall may not provide enough energy (i'm assuming there's some threshold) where snow crystal structure changes and layers begin to collapse, therefore the snow depth wouldn't be significantly affected.
A very quick search turned up no good articles on how and at what rate rainfall impacts the snowpack crystal/layer structure.
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- Amar Andalkar
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14 years 10 months ago #199345
by Amar Andalkar
Umm, Phil . . . because it was over 32 °F the whole time, and it didn't snow?? It looks like it never got below 34 °F, with a high of 40 °F.
Also, the heavy rain must have been rapidly flowing through the snowpack and not sitting inside it like a sponge, although the SWE temporarily did go up by about 0.8". But it is now decreasing as the remaining water flows out.
I don't know / haven't read any good references on that subject.
But the key is that the rainfall is providing almost no energy to the snowpack, only the tiny specific heat due to its temperature above freezing, and not any large latent heat (which is what advective energy usually refers to, in the context of hydrology -- it's latent heat stored in the air at one place and transported far away to be released at another place). That lack of available energy is why the rain is having no snowpack melting effect (it released all of its advective energy into the skies far above when it condensed out of the vapor).
As for layers and crystal structure, the snowpack at 3000 ft at Snoqualmie Pass even before this rain was pretty well consolidated into late-spring density, I'm assuming its density is between 0.4 and 0.5 (which I just confirmed by looking at some nearby SNOTEL sites, which have snowdepth and SWE). So there isn't really anything left to collapse or change, that snowpack is already nearly as dense as it's going to get before it melts in a few months. That's why the snowdepth isn't changing this time, but in the January 2009 case, the snowdepth decreased by 30" even though there was little melting, because that snowpack started out very wintry and unconsolidated.
Replied by Amar Andalkar on topic Re: More proof that rain doesn't really melt snowpack
I looked at the Buckinghorse snotel this morning when Gary posted a link to it.
How come it got 14 inches of precip, but almost no increase in SWE?
www.wcc.nrcs.usda.gov/nwcc/sntl-datarpt....1107&days=7&state=wa
Umm, Phil . . . because it was over 32 °F the whole time, and it didn't snow?? It looks like it never got below 34 °F, with a high of 40 °F.
Also, the heavy rain must have been rapidly flowing through the snowpack and not sitting inside it like a sponge, although the SWE temporarily did go up by about 0.8". But it is now decreasing as the remaining water flows out.
Amar, do you have any material on how rainfall may reorganize/redistribute crystal structure in the snowpack?
Certainly the rainfall is providing some advective energy into the snowpack causing the snow to melt. However the rainfall may not provide enough energy (i'm assuming there's some threshold) where snow crystal structure changes and layers begin to collapse, therefore the snow depth wouldn't be significantly affected.
A very quick search turned up no good articles on how and at what rate rainfall impacts the snowpack crystal/layer structure.
I don't know / haven't read any good references on that subject.
But the key is that the rainfall is providing almost no energy to the snowpack, only the tiny specific heat due to its temperature above freezing, and not any large latent heat (which is what advective energy usually refers to, in the context of hydrology -- it's latent heat stored in the air at one place and transported far away to be released at another place). That lack of available energy is why the rain is having no snowpack melting effect (it released all of its advective energy into the skies far above when it condensed out of the vapor).
As for layers and crystal structure, the snowpack at 3000 ft at Snoqualmie Pass even before this rain was pretty well consolidated into late-spring density, I'm assuming its density is between 0.4 and 0.5 (which I just confirmed by looking at some nearby SNOTEL sites, which have snowdepth and SWE). So there isn't really anything left to collapse or change, that snowpack is already nearly as dense as it's going to get before it melts in a few months. That's why the snowdepth isn't changing this time, but in the January 2009 case, the snowdepth decreased by 30" even though there was little melting, because that snowpack started out very wintry and unconsolidated.
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- philfort
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14 years 10 months ago #199346
by philfort
Replied by philfort on topic Re: More proof that rain doesn't really melt snowpack
With a snowpack around 200 inches, it seems very suprising that water would drain out so quick. I would expect it to add to the SWE and just make the snow denser?
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- trees4me
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14 years 10 months ago #199349
by trees4me
Replied by trees4me on topic Re: More proof that rain doesn't really melt snowpack
In general I disagree that rainfall doesn't have enough energy to melt snow. The rain is providing energy to the snowpack. However, the amount of energy certainly varies signficantly by event. Both the amount of energy the rain has when it hits the snowpack (temperature driven) and the snowpack structure play important roles. Once the winter layers are broken down then the rain will have developed pathways to travel through the snowpack to the ground. This allows for less energy transfer since there's less surface area contact between the rain and the snow once these little "tunnels" have developed.
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