WSDOT - Only 80" of Snow at Snoq Pass this Winter

Many of the stations are located in sheltered sites on generally flat ground. These locations improve accuracy of snowfall/precipitation measurements, though they often hold snow a bit longer than exposed sites. The Alpental station is located behind the main lodge. If the site hasn't been recently maintained then we may be seeing interference from brush

Thanks!

...

So what about the snowfall this year: obviously a freakish anomaly of the highest order, especially so at Snoqualmie Pass. With 1" of new snowfall recorded today (the first snowfall there in the entire month of March!?!), the total now stands at 81". How likely is significant additional snowfall? Current forecasts for the next week pretty much rule out additional snowfall this month at Snoqualmie, although heavy precip is certain for tomorrow, along with significant snowfall at higher elevations, and there may be a couple more systems on Friday and Monday which bring snow higher up. So on to April and May:

Average snowfall at Snoqualmie Pass in April and May is about 30" as shown in the data, but median snowfall is only 20" with a standard deviation of almost 30". The maximum April-May snowfall is 97" (in April 1955, followed by 0" that May), while the minimum April-May snowfall is 0" in several years. Which is to say, spring snowfall at Snoqualmie Pass is extremely fickle and variable, and quite likely to end up under 20". Since the median is 20", statistically there is only about a 50% chance of Snoqualmie breaking 100" this season. Given the lack of any indication from climate models of a cooler and wetter than normal April this year, the real chance is probably well under 50% at this point. And the likelihood of this year matching the previous record low of 172" is minuscule, statistically on the order of 1%, and realistically well under that.

Assuming it does end up under 100", how unusual, how statistically unlikely would such a total be? The previous record low in a complete season was 172" in 1941-42, trailed closely by 196" in 1940-41 and 191" in 1976-77. So a sub-100" snowfall would be a very extreme outlier at roughly half the previous low. Given the median snowfall of 413" over the full period of record with a standard deviation of 130", a total of 90" would be about 2.5 standard deviations below the median, which is in the 0.6 percentile, or roughly 1 in 160 years!!

That's all based on a normal distribution though, and annual snowfall totals are not "normally" distributed, but it's good enough for a rough approximation of how unlikely a sub-100" snowfall total would be. To verify that, let's see how many years fall under 220", which is 1.5 standard deviations below the median, or 6.7 percentile, roughly 1 in 15 years. Out of the 95 complete years, 6 of them are under 220", which matches the statistical expectation well. So this calculation method seems reasonable despite the snowfall totals not being normally distributed. And given that there are nearly 100 years of data, it's quite reasonable to encounter a 1 in 160 year event in such a data set.

So maybe statistics are pretty useful for this sort of thing?! The roughly 50% statistical chance of breaking 100" did in fact come true, despite all meteorological indications to the contrary. All it took was one strong convergence-zone snowstorm on the night of March 31 to April 1, with snowfall rates of 2-3" per hour for a few hours at its peak, and 15" new for the day. From www.wsdot.com/winter/snoqualmie/ :



The current season total of 100" is still about 2.4 standard deviations below the median (413" over the full period of record with a standard deviation of 130"), which is in the 0.8 percentile, or roughly 1 in 120 years!

On a side note, it looks like Snoqualmie Pass will make it through this entire season with ZERO hours of avalanche-control closures:



Here's the recent daily snowfall from i90.atmos.washington.edu/roadview/avalanche/hyak.htm (note that it's not measured at Hyak, but at Snoqualmie Pass 3000 ft):
[tt]
Snoqualmie Snowfall Report
Courtesy of WSDOT Hyak Operation Center

Date        New Snow   Snow Depth

---

Mon Apr 13    0 in       0 in
Sat Apr 11    0 in       0 in
Thu Apr 09    0 in       0 in
Wed Apr 08    0 in       0 in
Tue Apr 07    0 in       0 in
Mon Apr 06    0 in       0 in
Fri Apr 03    0 in       4 in
Thu Apr 02    1 in       9 in  <<< Reaches 100" for season!
Wed Apr 01   15 in      15 in
Tue Mar 31    0 in       0 in
Fri Mar 27    0 in       0 in
Wed Mar 25    3 in       3 in
Tue Mar 24    1 in       1 in  <<< First snowfall in March!
Mon Mar 23    0 in       0 in
Fri Mar 20    0 in       0 in
Thu Mar 19    0 in       0 in
Wed Mar 18    0 in       0 in
Tue Mar 17    0 in       0 in

---

[/tt]
Although the Puget Sound convergence zone was kind to Snoqualmie that time, this weekend it missed Snoqualmie entirely, staying farther north and dumping 16" new at Stevens Pass from midday on April 11 into April 12, with similar snowfall rates of 2-3" per hour at its peak. Snoqualmie got relatively little precip from the weekend storm, almost all of which fell as rain at pass level, with only trace amounts of snow.

And here's the NWAC telemetry at Snoqualmie and Alpental over the 2-day period of that March 31 to April 1 storm, saved for posterity:
[tt]
Northwest Avalanche Center
Washington Department of Transportation
Snoqualmie Pass, Washington
3770' 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
             3760' 3770' 3010' 3010' 3760' 3760' 3760' 3010' 3010' 3010' 3010' 3010'

---

  3 31   500    35    34    36    94    21    37   262   .04   .04     0     0  1013
  3 31   600    33    32    35    93    24    47   250   .01   .05     0     1  1014
  3 31   700    32    31    35    96    15    28   247   .03   .08     0     0  1014
  3 31   800    31    31    33    96    12    20   246   .05   .13     0     0  1015
  3 31   900    30    31    33    95    18    27   250   .05   .18     0     0  1016
  3 31  1000    31    32    37    92    13    24   257     0   .18     0    -0  1016
  3 31  1100    31    33    35    93    10    15   250   .02    .2     0     0  1017
  3 31  1200    31    34    34    96     8    13   249   .09   .29     0     1  1017
  3 31  1300    32    34    37    94     6    14   256   .02   .31     0     0  1017
  3 31  1400    32    31    33    96    14    45 -7999   .04   .35     0     1  1018
  3 31  1500    31    30    32    97    14    23   280   .07   .42     0     1  1018
  3 31  1600    32    31    32    97    12    19   272   .04   .46     0     0  1018
  3 31  1700    31    31    32    97     9    18   249   .07   .53     0     0  1018
  3 31  1800    30    31    32    98     5    15   246   .09   .62     0     0  1018
  3 31  1900    29    30    31    98     8    19 -7999   .13   .75     2     4  1019
  3 31  2000    30    30    31    98     5    13 -7999   .16   .91     2     4  1019
  3 31  2100    30    30    32    98     7    16   309   .14  1.05     3  -165  1019
  3 31  2200    30    30    31    98     9    20   286   .15   1.2     5  -165  1020
  3 31  2300    29    30    31    98    11    18   270   .14  1.34     8     9  1020
   4 1     0    30    30    31    98     8    17 -7999   .11  1.45    10    13  1020
   4 1   100    30    29    31    98    15    24   253   .14  1.59    10    13  1020
   4 1   200    30    29    30    98    14    31   259   .11   1.7    10    14  1021
   4 1   300    29    29    31    98     9    15   257   .13  1.83    11    13  1021
   4 1   400    28    29    30    98    11    16   254   .14  1.97    10    14  1021

---

   4 1   500    29    29    30    98     7    16   252   .17   .17     0    14  1021
   4 1   600    28    29    30    98    11    21   254   .08   .25     0    15  1022
   4 1   700    29    29    32    97     7    12   253   .03   .28     0    14  1022
   4 1   800    30    30    33    95     8    11   256   .06   .34     0    14  1022
   4 1   900    30    33    36    86    10    17   250   .03   .37     0    13  1023
   4 1  1000    31    34    37    87    11    19   248     0   .37     0    12  1023
   4 1  1100    32    32    39    82     7    16   265     0   .37     0    13  1023
   4 1  1200    32    34    38    83     3     8 -7999     0   .37     0    10  1023
   4 1  1300    33    35    42    75     6    18   264     0   .37    -0     9  1022
   4 1  1400    32    35    45    70     8    13 -7999     0   .37     0     8  1022
   4 1  1500    33    35    39    82    12    22   249     0   .37     0     9  1022
   4 1  1600    32    32    36    92     8    17   270   .01   .38     0     9  1022
   4 1  1700    31    33    35    94     8    15   247   .03   .41     0    10  1022
   4 1  1800    31    31    35    93    10    18   255   .02   .43     0     9  1022
   4 1  1900    31    31    32    97    15    22   249   .01   .44     0     9  1023
   4 1  2000    31    30    32    97    12    19   250   .03   .47     0     9  1023
   4 1  2100    30    30    32    97    12    19   255   .02   .49     0     9  1023
   4 1  2200    29    30    31    98     8    15   244     0   .49     0     9  1024
   4 1  2300    30    29    31    98     9    15   258     0   .49     0     8  1024
   4 2     0    29    29    31    98     7    13   253     0   .49     0     9  1024
   4 2   100    29    29    32    98     9    13   246     0   .49     0     8  1024
   4 2   200    29    29    32    98     8    15   242     0   .49     0     8  1024
   4 2   300    29    30    32    98     7    11   243     0   .49     0     8  1024
   4 2   400    29    29    31    98     8    12   235     0   .49     0     8  1024

---

Northwest Avalanche Center
Alpental Ski Area, Washington
Wind gages unheated and may rime
5470' Intermittent snow out

MM/DD  Hour  Temp  Temp  Temp    RH    RH  Wind  Wind  Wind  Hour Total 24 Hr Total 24 Hr Total Inter
         PST     F     F     F     %     %   Avg   Max  Dir. Prec. Prec.  Snow  Snow  Snow  Snow  Snow
             5470' 4350' 3100' 3100' 5470' 5520' 5520' 5520' 3100' 3100' 3100' 3100' 4350' 4350' 5470'

---

  3 31   500    28    33    37    96   100    26    45   235   .03   .03     0    13     0    25    39
  3 31   600    26    32    36    97    99    20    37   235   .01   .04     0    13     0    24    37
  3 31   700    26    32    35    98   100    19    32   234   .02   .06     0    14     0    21    39
  3 31   800    27    31    33    99    99    14    24   234   .08   .14     0    14     1    21    39
  3 31   900    27    31    34    99    98    18    31   234   .05   .19     0    14     2    22    38
  3 31  1000    29    33    36    92    96    19    33   235   .01    .2     0    13     2   283    35
  3 31  1100    28    33    35    96    97    15    27   236   .01   .21     0    13     2   283    29
  3 31  1200    29    32    34    98    97    16    31   236   .09    .3     0    13     2   283    27
  3 31  1300    27    34    36    96    98    20    36   235   .02   .32     0    13     2    23    17
  3 31  1400    26    32    33    98    99    20    40   238   .05   .37     0    13     2    23   -27
  3 31  1500    26    32    33    99    99    16    26   234   .06   .43     0    12     4   283  -170
  3 31  1600    26    32    33    99    99    17    31   234   .04   .47     1    14     4    24  -224
  3 31  1700    26    31    33    99    98    11    21   237   .09   .56     1    12     5   283  -132
  3 31  1800    25    30    33    99    98    11    24   234   .12   .68     0    14     5    26   -74
  3 31  1900    24    29    32    99    98    11    14   241   .13   .81     0    17     7    28   -39
  3 31  2000    25    29    33   100    98     7    11   237   .15   .96     4    16     7    27   -18
  3 31  2100    24    29    32    99    98     9    21   234   .12  1.08     4    18     8    32    -6
  3 31  2200    24    29    33   100    99    11    16   235   .17  1.25     6    20    11   283     4
  3 31  2300    24    29    32   100    99    10    20   232   .14  1.39     8    26    14   283     9
   4 1     0    24    29    32   100    98    13    22   228   .12  1.51     8    29    16    39    10
   4 1   100    24    29    32   100    99    15    27   235   .16  1.67     8    28    17    41   -51
   4 1   200    24    28    32   100    99    16    28   234   .11  1.78     8    28    17   283   -31
   4 1   300    24    28    32   100    99    15    32   233   .13  1.91     8    21    17   283   -16
   4 1   400    23    28    31   100    98    14    26   234   .14  2.05     7    28    17   283    -6

---

   4 1   500    23    28    32    99    98    11    19   234   .14   .14     8    28    18   283     1
   4 1   600    24    28    31   100    98    11    28   234   .09   .23     0    28    18   283     7
   4 1   700    24    28    33    98    99    12    23   233   .06   .29     0    31    18    41    11
   4 1   800    26    29    33    95    99    10    20   234   .04   .33     0    33    18   283    13
   4 1   900    31    32    34    95    99    10    17   233   .02   .35     0    32    18   283    12
   4 1  1000    32    33    35    93    98     7    13   234   .02   .37     0    32     0    42     7
   4 1  1100    34    35    39    85    98    11    20   234   .02   .39    -0    59     0    41   -20
   4 1  1200    33    35    39    86    93     8    15   236   .01    .4    -0    66     0    36   -45
   4 1  1300    34    36    39    88    91    10    19   237     0    .4     0    72     0    38   -32
   4 1  1400    35    37    39    85    89    10    21   248   .01   .41     0    74     0    35   -26
   4 1  1500    30    36    39    89    94     8    15   254     0   .41     0    74     0    38   -78
   4 1  1600    28    34    35    94    97    11    20   250   .02   .43     0    75     0    36   -10
   4 1  1700    29    33    34    95    95    11    18   235   .02   .45     0    75     0   283     2
   4 1  1800    28    32    34    96    97    12    20   237   .03   .48     0    75     1   283     7
   4 1  1900    26    31    33    98    98    13    22   232   .04   .52     0    75     0   283   -80
   4 1  2000    26    31    33    98    99    14    26   247   .04   .56     0    75     2   283   -67
   4 1  2100    25    30    33    99    98    16    27   291   .02   .58     0    72     2   283   -29
   4 1  2200    24    29    32    99    97    16    28   345     0   .58     0    74     2   283   -13
   4 1  2300    23    28    32   100    99    18    26   345     0   .58     0    74     2    41    -8
   4 2     0    23    28    32    99    97    18    27   347     0   .58     0    74     2    42    -6
   4 2   100    24    28    32    99    98    12    20   348     0   .58     0    74     2    41    -4
   4 2   200    24    29    32    99    98     7    17   325     0   .58     0    74     2    41    -4
   4 2   300    24    29    32    99    98    12    23   345     0   .58     0    74     2    38    -4
   4 2   400    24    29    32    99    97     7    14   327     0   .58     0    74     2    38    -5

---

[/tt]

Not directly related to Snoqualmie Pass, but my favorite benchmark to judge the decline of the Cascade snowpack is to look at the glaciers.

Statistics may lie, but glaciers don't.

Glaciers may not lie, but they may instead be telling us something different than what we might initially assume.

Clearly glacial recession is proof of a significant decline in snowpack -- but snowpack on what date, and at what elevation? Glacier mass balance depends only on the snowpack remaining in the accumulation zone as of the end of summer, prior to start of the next season's snowfall. At elevations above 6500-8000 ft in the Cascades where the accumulation zones of all glaciers in the range sit, that date is sometime from about September to October in most years, and as late as November in rare years with extremely dry September-Octobers. Only the snowpack which exists in its accumulation zone matters to a glacier's health, while snowpack lower down on the glacier has almost no effect, and snowpack below or off the glacier none at all.

It is well known that glacial mass balance, and glacial recession or expansion, depend very strongly on summer temperatures and cloudiness. A very cool cloudy summer such as the one we had in 2010 following a fairly average snowpack season can result in significant positive mass balance. Much more so than other years like 2008 which by any measure was a huge snowpack year in the Northwest, especially so at low elevations, but with normal warm summer weather resulted in much less gains for the glaciers. An extended pattern of very cool and cloudy summers can result in significant glacial expansion, even with no increase in wintertime snowpack above average levels over that period, while a run of hot sunny dry summers will cause significant glacial recession even if the preceding winter snowpacks were all well above-normal.

So glacial mass balance and glacial recession really tell us nothing about the overall winter snowpack, or at most very little, and they tell us absolutely nothing about the low-elevation snowpack (roughly 1500-3500 ft in the WA Cascades) and even the mid-elevation snowpack (roughly 3500-5500 ft), which lie far below their accumulation zones. As we have seen so clearly during the 2014-15 season, the low-elevation snowpack (extremely below-normal this year) can be highly uncorrelated from the mid- and high-elevation snowpack (way closer to normal this year above 5000 ft), and that relative lack of correlation holds true in many other seasons too, albeit to a lesser degree than this freakish season.

In a typical year the Snoq area used to be a goto place. Easy to get to, no gate issues, lots of choices as long as the snowpack is deep in the low elevations. This year I did not make one trip there. I hate tearing up my ski bases. The prior year I also found myself avoiding Snoq.

What has been happening at Snoq is quite disconcerting. Even the prior season skiing was limited for Snoq in the opportunities for decent skiing. In recent years January has been pathetic. Sadly I do not see this situation getting any better.

This year was a disaster and sadly some of the prognostications for next year are not very good. It might be in a decade Snoq will essentially be unskiable for a good portion of the ski season.

If people are not seeing this shift they are not being honest the times they are a changin.

In a typical year the Snoq area used to be a goto place. Easy to get to, no gate issues, lots of choices as long as the snowpack is deep in the low elevations. This year I did not make one trip there. I hate tearing up my ski bases. The prior year I also found myself avoiding Snoq.

What has been happening at Snoq is quite disconcerting. Even the prior season skiing was limited for Snoq in the opportunities for decent skiing. In recent years January has been pathetic. Sadly I do not see this situation getting any better.

This year was a disaster and sadly some of the prognostications for next year are not very good. It might be in a decade Snoq will essentially be unskiable for a good portion of the ski season.

If people are not seeing this shift they are not being honest the times they are a changin.

In 2008 Snoqualmie had over 600" and both 2010 and 2011 they opened in November with average (aprox 400") seasons. 2005 was horrible and the past 2 were poor but it was worse from 1977-1981 and the 1940's were even worse then that. Just keep the glass half full, it will be back again.

Snoqualmie will be deep again soon. 'Till then, there's a huge playground out there. (Photo Thursday evening).