The History of Southern California Snow Conditions chart is the best expression I've devised for displaying the range and incidence of snow conditions. In order to construct such a chart it is necessary to have week by week reports of conditions. The snowfall data that I collect is monthly and not sufficient for this purpose. Through personal knowledge I only have sufficient info for Southern California and Mammoth.
The focus of these charts is to show coverage of terrain and frequency/consistency of packed powder snow that has not been through a melt/freeze. The weekly grades are not a measure of fresh powder, which cannot be predicted in advance for a specific week. In 2008 I derived a method to estimate percent of powder days from monthly snowfall. I now apply that percentage to all weeks rated A or B and show that percentage and an adjusted total grade at far right. I previously wrote an Inside Tracks article focusing on powder skiing.
The Mammoth chart would be very boring in its entirety, so I show here the 25th, 50th and 75th percentiles, plus 3 extreme seasons in each direction of my experience.
Definitions:
| A: |
| B: |
| C: |
| HISTORY OF MAMMOTH SNOW CONDITIONS | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Pwdr Adj | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Season/Month | October | November | December | January | February | March | April | May | June | July | Total | A | B | C | Pwdr | Total | ||||||||||||||||||||||||||||||||||||||||||||||||||
| 1982-83 | C | 1 | C | B | A | A | 9 | A | A | A | A | 12 | A | A | A | A | A | 15 | A | A | A | A | 12 | A | A | A | A | 12 | A | A | A | A | 12 | A | B | A | B | B | 12 | B | C | C | C | 5 | C | C | D | D | 2 | 92 | 25 | 30 | 37 | 26% | 127 | |||||||||||
| 2004-05 | B | B | 4 | B | A | A | A | 11 | A | A | A | A | 12 | A | A | A | A | A | 15 | A | A | A | A | 12 | A | B | A | A | 11 | A | A | A | B | B | 13 | A | B | B | B | 9 | C | C | C | C | 4 | C | 1 | 92 | 23 | 32 | 37 | 26% | 127 | |||||||||||||
| 1994-95 | D | D | D | D | 0 | D | C | B | A | 6 | A | A | A | A | 12 | A | A | A | A | A | 15 | A | A | A | B | 11 | A | A | A | A | 12 | A | A | A | B | B | 13 | B | A | B | B | 9 | C | B | C | C | 5 | C | C | C | C | D | 4 | 87 | 21 | 29 | 37 | 23% | 115 | |||||||
| 75th percentile | 0 | D | D | C | B | 3 | A | A | A | A | A | 15 | A | A | A | A | 12 | A | A | A | A | 12 | A | A | A | A | A | 15 | A | A | B | B | 10 | B | C | C | C | 5 | C | C | C | C | 4 | C | 1 | 77 | 20 | 24 | 33 | 19% | 98 | |||||||||||||||
| Median | 0 | D | D | C | 1 | C | B | B | B | A | 10 | A | A | A | A | 12 | A | A | A | A | 12 | A | A | A | A | A | 15 | A | B | B | B | 9 | C | C | C | C | 4 | C | 1 | 0 | 64 | 15 | 21 | 28 | 15% | 77 | ||||||||||||||||||||
| 25th percentile | 0 | D | D | 0 | D | D | C | C | B | 4 | B | B | A | A | 10 | A | A | A | A | 12 | A | A | A | B | B | 13 | B | B | B | C | 7 | C | C | C | C | 4 | 0 | 0 | 50 | 9 | 17 | 24 | 10% | 56 | ||||||||||||||||||||||
| 2006-07 | 0 | D | D | D | D | 0 | D | D | D | C | B | 3 | B | B | C | C | 6 | C | B | A | A | 9 | A | B | B | B | B | 11 | B | B | B | C | 7 | B | C | C | C | 5 | 0 | 0 | 41 | 3 | 15 | 23 | 10% | 45 | ||||||||||||||||||||
| 1986-87 | 0 | 0 | D | 0 | D | B | C | C | 4 | C | A | A | A | 10 | A | A | A | A | A | 15 | B | B | C | C | 6 | D | D | 0 | 0 | 0 | 35 | 8 | 11 | 16 | 10% | 40 | ||||||||||||||||||||||||||||||
| 1990-91 | 0 | D | 0 | D | D | D | D | C | 1 | C | C | D | D | 2 | D | D | D | D | 0 | A | A | A | A | A | 15 | A | B | B | B | 9 | B | B | C | C | 6 | 0 | 0 | 33 | 6 | 11 | 16 | 13% | 38 | |||||||||||||||||||||||
| Squaw Median | 0 | D | C | 1 | C | C | B | B | B | 8 | A | A | A | A | 12 | A | A | B | A | 11 | B | A | B | A | B | 12 | B | B | B | C | 7 | C | C | D | D | 2 | 0 | 0 | 53 | 9 | 19 | 25 | 17% | 64 | ||||||||||||||||||||||
Results/Comments:
Mammoth's strongest point is snow preservation.
The average percent of terrain that is packed powder/winter snow is
78% mid-March and 58% first of April. And only 6 of the past 40
seasons were majority spring conditions mid-March, though 3 of
those were in the past 5 years. Snow preservation also results in
staying open to Memorial Day in 90% of seasons and 4th of July in
the top 30%.
Mammoth has some favorable attributes in early season also. Average snowfall is high, it almost never rains, lower slopes are mostly intermediate and the steep upper slopes often get extra blown-in snow. Thus about 75% of terrain is usually skiable on a 3-4 foot base. Working against early season reliability is the well known volatility of Sierra snowfall. If an extended dry spell hits in November/December, the early season can be very restricted. In the worst quarter of seasons full operation will be attained mid-January or later.
The extreme seasons illustrate the snowfall volatility. In 2004-05 Mammoth had a 56-inch dump Oct. 20-22 and only staffing considerations prevented the entire mountain from opening immediately. In 1982-83 October snowfall was more modest, but it continued into November so full operation was still attained before Thanksgiving. Then it snowed every week from mid-January to mid-May, producing an incredible 25 weeks (half a calendar year!) with powder/packed powder conditions. 1994-95 has the record for both October 8 earliest opening and August 13 latest close. But that October snowfall was also modest and the first big dump was in late November. Not shown but also scoring about 90 (before powder adjustment) would be 1981-82, which started similar to 1982-83 and finished with a 12-inch storm on June 30 for the closing July 4 weekend.
On the negative side 1986-87 and 2006-07 are examples of Mammoth not getting its first major dump until February. 1986-87 looks worse mainly because Mammoth did not have snowmaking then, and now it has a sizeable reservoirs and a portable system that can be used where it's most needed. But 2006-07 also had a hot March that brought spring conditions much earlier than normal. In 1990-91 the big dumps did not come until March, but the March snowfall was 197 inches so the late season was as good as a normal year. 1975-76 was before my time but had to be similar to 1986-87 based upon snowfall incidence. 1976-77 was nearly a total wipeout, with no snow before New Year's, only 90 inches January to March, then 2-3 feet in May. 1976-77 probably would have scored in the 10-15 range.
Other Sierra Ski Areas
So how do Lake Tahoe resorts compare? The Sierra Crest west of Tahoe gets
about 20% more snow than Mammoth, so the snowiest areas Kirkwood,
Sugar Bowl and Alpine Meadows have an early season profile as good
as Mammoth's with the extra snow offsetting Mammoth's higher
altitude/no rain advantage. The biggest areas Squaw Valley and
Heavenly are slower to get fully open than Mammoth due to lower
snowfall at Heavenly and much higher coverage needed (6-8 feet) on
Squaw's expert skewed terrain. Squaw's median is shown accordingly.
Squaw is 2,000 feet lower than Mammoth with a lower percentage of
north facing slopes, so spring conditions develop much earlier. I
show the median as a "checkerboard pattern" of alternating A's and
B's starting mid-February. This does not imply that the A weeks are
better than the B weeks. It shows that you can expect spring
conditions if it hasn't snowed recently, but that snowfall is still
abundant until April when the chart shows all B's. Also keep in
mind that the high snowfall variability applies throughout the
Sierra, so the high and low seasons may be as far from the median
as at Mammoth.
More Snow Conditions Charts
Vermont
Fernie and Whistler
Utah
Colorado