Mammoth Mountain Ski Patrol 2010-11 Storm Summary - Sesame Snow Study Site 9,000' (2,743m)
Date New Snow Base Depth SWE Rain % Density Storm Snow Storm SWE Season Snow Season Precip Base Hi Temp Base Lo Temp Notes
10/5/2010 4.0 4.0 0.44   11 4.0 0.44 4.0 0.44     Measurements from Mammoth Pass.
                         
10/24/2010       0.76       4.0 1.20     Three days of heavy rain mixed with some sleet at 9000'.  Resulted in very hard, thick rain crust to at least 11000'.
10/25/2010       2.44       4.0 3.64     Measurements from Mammoth Pass.
10/26/2010       0.36       4.0 4.00      
                         
10/30/2010 5.0 7.0 0.65   13 5.0 0.65 9.0 4.65 45 25 Depth sensors online at Sesame, SWE estimated.
                         
11/8/2010 11.0 12.5 1.70   16 11.0 1.70 20.0 6.35 33 19  
                         
11/10/2010 2.0 12.0 0.25   13 2.0 0.25 22.0 6.60 38 22  
11/11/2010 2.0 13.0 0.34   17 4.0 0.59 24.0 6.94 28 16  
                         
11/20/2010 13.0 20.0 1.75   13 13.0 1.75 37.0 8.69 38 20  
11/21/2010 21.0 32.0 1.68   8 34.0 3.43 58.0 10.37 22 10  
11/22/2010 10.5 39.0 0.90   9 44.5 4.33 68.5 11.27 15 10  
11/23/2010 6.0 34.0 0.58   10 50.5 4.91 74.5 11.85 19 13  
11/24/2010 9.0 40.0 0.88   10 59.5 5.79 83.5 12.73 18 11  
                         
11/28/2010 9.0 39.5 1.00   11 9.0 1.00 92.5 13.73 26 8  
                         
Date New Snow Base Depth SWE Rain % Density Storm Snow Storm SWE Season Snow Season Precip Base Hi Temp Base Lo Temp Notes
12/4/2010 1.0 32.0 0.09   9 1.0 0.09 93.5 13.82 44 27  
12/5/2010 2.0 33.5 0.25   13 3.0 0.34 95.5 14.07 32 27  
                         
12/6/2010 11.5 43.5 1.37   12 11.5 1.37 107.0 15.44 35 24 Widespread breakable wind crust.  Moderate avalanche activity.
                         
12/9/2010 0.0 38.0 0.00 0.28 - - 0.28 107.0 15.72 40 31 Rain turned to snow at 9,000' at approx. 8:40 12/9.
12/10/2010 1.0 38.0 0.53   53 1.0 0.81 108.0 16.25 35 32 Mixed rain and snow at 9,000'.
                         
12/15/2010 12.5 46.0 1.85   15 12.5 1.85 120.5 18.10 36 25  
12/16/2010 1.5 45.5 0.21   15 14.0 2.06 122.0 18.31 28 11 Surface hoar in Hemlock and the Bear.  Minimal avalanche activity on the upper mountain, Lincoln and Drangon's Back quite active.
                         
12/17/2010 6.0 49.5 0.60   10 6.0 0.60 128.0 18.91 31 11  
12/18/2010 31.5 78.5 3.45   11 37.5 4.05 159.5 22.36 29 23 Extremely sensitive avalanche conditions, failing in storm layer and running a very long distance.
12/19/2010 31.5 98.5 3.96   13 69.0 8.01 191.0 26.32 31 25 Very sensitive soft slab avalanches, running in new snow. 
12/20/2010 28.5 116.5 3.48   12 97.5 11.49 219.5 29.80 30 17 Density of snow decreased dramitically overnight.  Density of surface snow perhaps 7%.  Widespread sloughing.
12/21/2010 21.0 128.5 2.05   10 118.5 13.54 240.5 31.85 22 17 Clouds cleared by ~8:00.  Evidence of widespread avalanche activity throughout.  Began snowing again ~11:00.
12/22/2010 9.0 127.5 0.71   8 127.5 14.25 249.5 32.56 26 19  
12/23/2010 2.0 123.5 0.18   10 129.5 14.43 251.5 32.74 31 18 Sun was shining PM 12/22, although summit was still obstructed.  Widespread surface sloughing.
                         
12/26/2010 5.0 118.0 0.60   12 5.0 0.60 256.5 33.34 39 16 Very strong SW wind.
                         
12/29/2010 29.5 135.5 3.33   11 29.5 3.33 286.0 36.67 34 22 New record for monthly snowfall, 193.5".  Many natural avalanches and paths running much farther than usual.
12/30/2010 4.0 134.5 0.43   11 33.5 3.76 290.0 37.10 23 -2 Strong uplslope NE wind.
                         
Date New Snow Base Depth SWE Rain % Density Storm Snow Storm SWE Season Snow Season Precip Base Hi Temp Base Lo Temp Notes
1/1/2011 1.5 128.0 0.14   9 1.5 0.14 291.5 37.24 24 3  
1/2/2011 10.5 134.0 1.03   10 12.0 1.17 302.0 38.27 25 12  
1/3/2011 1.5 132.0 0.09   6 13.5 1.26 303.5 38.36 22 11 Moderate NE upslope wind.
                         
1/12/2011 4.0 119.5 0.44   12 4.0 0.44 307.5 38.80 32 23  
                         
1/30/2011 9.5 111.5 0.50   5 9.5 0.50 317.0 39.30 41 18 Unusually warm and dry January.  Most areas covered by firm wind and/or melt-freeze crusts.
1/31/2011 1.0 110.5 0.08   7 10.5 0.58 318.0 39.38 23 14 Strong NE upslope wind, top of mountain scoured.
                         
2/16/2011 6.0 101.5 1.02   17 6.0 1.02 324.0 40.40 35 20  
2/17/2011 7.0 114.0 0.59   8 13.0 1.61 331.0 40.99 25 9  
2/18/2011 28.0 137.5 2.08   7 41.0 3.69 359.0 43.07 19 10  
2/19/2011 24.0 149.0 1.93   8 65.0 5.62 383.0 45.00 26 16  
                         
2/21/2011 1.5 139.0 0.18   9 1.5 0.18 384.5 45.18 20 4  
                         
2/25/2011 12.0 139.0 1.00   8 12.0 1.00 396.5 46.18 21 14  
2/26/2011 18.5 151.0 2.70   15 30.5 3.70 415.0 48.88 21 5 Temperature dropped dramatically after the majority of the snow had fallen.
                         
Date New Snow Base Depth SWE Rain % Density Storm Snow Storm SWE Season Snow Season Precip Base Hi Temp Base Lo Temp Notes
3/2/2011 6.5 142.0 0.75   12 6.5 0.75 421.5 49.63 40 23  
3/3/2011 7.5 147.5 1.15   16 14.0 1.90 429.0 50.78 31 22 Graupel covered with dense snow.
                         
3/6/2011 4.0 143.5 0.65   16 4.0 0.65 433.0 51.43 42 25  
3/7/2011 8.5 149.5 1.22   15 12.5 1.87 441.5 52.65 32 21 Firm crust approximately 2 inches from bottom of new snow.  Ice on storm board.
                         
3/14/2011 1.5 137.5 0.18   13 1.5 0.18 443.0 52.83 35 28  
                         
3/15/2011 0.5 135.0 0.07   13 0.5 0.07 443.5 52.90 35 29  
                         
3/16/2011 5.5 136.5 0.87   16 5.5 0.87 449.0 53.77 40 30 Ice on storm board.
3/17/2011 2.5 142.0 0.37   16 8.0 1.24 451.5 54.14 30 16  
                         
3/19/2011 17.0 155.0 1.50   9 17.0 1.50 468.5 55.64 29 18  
3/20/2011 21.5 168.0 2.02   9 38.5 3.52 490.0 57.66 21 12  
3/21/2011 26.5 188.0 2.44   9 65.0 5.96 516.5 60.10 22 15 Strong SW wind.
3/22/2011 4.5 184.5 0.30   7 69.5 6.26 521.0 60.40 18 12 Clean, easy shear in top two inches on tilted storm board.
                         
3/23/2011 7.0 183.0 0.56   8 7.0 0.56 528.0 60.96 25 13 Weather cleared afternoon of 3/22 and all paths were skier compacted.
3/24/2011 21.0 198.5 2.16   10 28.0 2.72 549.0 63.12 23 13  
3/25/2011 27.0 213.5 2.45   9 55.0 5.17 576.0 65.57 21 12 Storm cleared
                         
3/26/2011 6.5 206.5 0.95   15 6.5 0.95 582.5 66.52 23 12 broke snowfall record
3/27/2011 6.5 205.0 0.69   11 13.0 1.64 589.0 67.21 25 18 Strong SW wind.  Thick wind slab, cornice and sastrugi formation.
                         
Date New Snow Base Depth SWE Rain % Density Storm Snow Storm SWE Season Snow Season Precip Base Hi Temp Base Lo Temp Notes
4/3/2011 Trace 172.5 0.10   - Trace 0.10 589.0 67.31 45 28  
                         
4/6/2011 Trace 161.5 0.07   - Trace 0.07 589.0 67.38 45 29 Thin layer of graupel.
                         
4/7/2011 8.5 166.0 0.69   8 8.5 0.69 597.5 68.07 43 18  
4/8/2011 2.5 170.0 0.25   10 11.0 0.94 600.0 68.32 19 -1  
                         
4/9/2011 6.5 175.0 0.41   6 6.5 0.41 606.5 68.73 16 -1  
                         
4/13/2011 1.0 161.0 0.11   10 1.0 0.11 607.5 68.84 39 22 Broken stellars over ~3/4" of graupel.
4/14/2011 1.0 163.0 0.13   13 2.0 0.24 608.5 68.97 23 12 Very strong SW wind.  Lots of stripping and loading all over mountain.
                         
4/18/2011 Trace 150.0 0.12   - Trace 0.12 608.5 69.09 49 29 Mixed rain and graupel.
4/19/2011 Trace 149.0 0.04   - Trace 0.16 608.5 69.13 38 29 Mixed rain and graupel.
                         
4/21/2011 6.0 151.0 1.17   19 6.0 1.17 614.5 70.30 33 27 2" of graupel mixed with rain 4/20 afternoon followed by ~4" of graupel.  Ice crust on new snow board.
                         
4/23/2011 2.0 152.0 0.38   17 2.0 0.38 616.5 70.68 38 25  
4/24/2011 2.0 153.5 0.47   23 4.0 0.85 618.5 71.15 31 28 100% 4F 2-3mm graupel. Ice crust on new snow board.
                         
Date New Snow Base Depth SWE Rain % Density Storm Snow Storm SWE Season Snow Season Precip Base Hi Temp Base Lo Temp Notes
5/8/2011 6.0 129.5 0.84   14 6.0 0.84 624.5 71.99 49 25  
5/9/2011 Trace 128.0 -   - 6.0 0.84 624.5 71.99 29 18  
5/10/2011 2.0 130.0 0.20   10 8.0 1.04 626.5 72.19 26 19  
5/11/2011 0.5 127.5 0.08   16 8.5 1.12 627.0 72.27 43 25  
                         
5/15/2011 6.0 125.0 0.56   9 6.0 0.56 633.0 72.83 42 17  
5/16/2011 3.5 129.0 0.34   10 9.5 0.90 636.5 73.17 22 15  
                         
5/17/2011 4.0 128.0 1.00   25 4.0 1.00 640.5 74.17 30 21 Most of the new snow was graupel.
5/18/2011 8.5 138.0 1.48   17 12.5 2.48 649.0 75.65 25 21  
                         
5/19/2011 1.5 134.0 0.20   13 1.5 0.20 650.5 75.85 34 20  
                         
5/29/2011 5.0 115.5 0.50   10 5.0 0.50 655.5 76.35 37 17  
5/30/2011 1.0 115.0 0.10   10 6.0 0.60 656.5 76.45 30 15  
                         
6/2/2011 Trace 110.0 -   - Trace - 656.5 76.45 32 21  
                         
6/5/2011 3.0 109.5 0.75   26 3.0 0.75 659.5 77.20 39 32  
6/6/2011 2.0 108.0 0.47   25 5.0 1.22 661.5 77.67 44 27  
                         
6/29/2011 0.0 27.0   0.24       661.5 77.91 56 38 1-3" of very soggy snow on ch3 traverse.
6/30/2011 0.0 26.5   0.50       661.5 78.41      
All observations are made in the morning, therefore all measurements are for new snow during approximately the previous 24 hours.
Units for Base Depth, New Snow, Storm Total, and Season Snowfall are in inches. 
SWE≡Snow Water Equivalent, the amount of water produced from melting a known volume of snow, measured in inches of H2O.
Units for 24 Hour Base Hi Temp and Base Lo Temp are degrees Fahrenheit.
Line breaks indicate clearing between storms, despite occasional consecutive days.