At elevations above 10,000 ft (3,050 m), over 80% of the mean annual precipitation falls as snow. On the valley floors, from 15 to 25% of the average precipitation is snow, with wide fluctuations from year to year in the snow-to-rain ratio. Regardless of the temperature of air masses moving onto land, rainfall is rare from November through April at White Mountain I and practically nonexistent from October through May at White Mountain II. Moreover, snow has been recorded, usually in amounts of less than 6 in (15 cm), in all of the warmest months from June through September at White Mountain II (see Table 1.5 for a summary of snowfall).
Average annual snowfall is low at the base of the mountains, with 9 in (23 cm) at Bishop, 12 in (30 cm) at Dyer, and 15 in (38 cm) at Deep Springs. It builds to 106 in (270 cm) at White Mountain I and 164 in (417 cm) at White Mountain II. As discussed earlier, annual totals are very likely higher at upper elevations north of White Mountain Peak. Maximum seasonal snowfall amounts have been 50–60 in (125–150 cm) at Bishop and Deep Springs, and a little less at Dyer, with low average precipitation in winter. Bishop has had a few seasons with no snowfall; the other lowland stations have had at least 1 in (2.5 cm) or more of snow in all years of
record. At higher elevations measurable snowfall certainly occurs every year. Seasonal totals, 1 October to 30 September, range from 170 in (432 cm) in 1969 to 48.5 in (123 cm) in 1960 at White Mountain I, and from 238 in (605 cm) in 1969 to 83 in (211 cm) in 1960, at White Mountain II. Maximum monthly falls are 76 in (193 cm) at White Mountain I, e.g., in January 1969, and 86 in (218 cm) at White Mountain II in December 1966. Maximum 24-hour totals are 38 in (97 cm) at I and 44 in (36.37 cm) at II, both on 6 December 1966. At White Mountain II, 76 in (193 cm) of snow fell on the two days 5–6 December. Daily accumulations of 10–24 in (25–60 cm) are not infrequent at higher elevation. These are impressive figures for any location in the world, though exceeded in the nearby Sierra Nevada, and winter travelers in the White Mountains should be aware of the difficulty and danger of being out in such intense snowstorms, commonly accompanied by high winds. Where snow has been measured for water equivalent in both stations, or elsewhere at high elevations, a ratio of about 10 in (25 cm) of snow, as it falls, to 1 in (2.5 cm) of water is common. In lieu of actual measurements of melted snow, a ratio of 10-to-1 (snow depth to water equivalent) has been used in the records from all stations. A 10% density is occasionally too high, but less commonly too low, for snowfall at the two mountain stations.
Continuous snow cover at elevations above 10,000 ft (3,050 m) usually begins in late October or mid-November but can begin as early as the end of September and as late as February. Disappearance of snow cover usually occurs in May or June at White Mountain I, and in June or July at White Mountain II. Average duration of snow cover is about 160 days at the lower station and 210 days at the higher locations, but there is great variation from year to year, with a range at White Mountain II of 292 days in 1973 to 54 days in 1964. Snow depths at upper elevations generally increase until March or April, and occasionally May. Maximum recorded depth at White Mountain I is 94 in (239 cm), in March 1969, and 123 in (312 cm) at White Mountain II, in the same month. A measurement of 144 in (366 cm) was made with a snow sampler at Chiatovich Flats, at 10,600 ft (3,230 m), in March 1967. It is difficult to measure accurately such parameters as snowfall, snow cover, and snow depth; significant differences can occur in short horizontal distances. Much depends on the location and exposure of the site, the instruments used, the times of observation, and the knowledge, persistence, and hardiness of the observer. It is commonly difficult to differentiate snow that has fallen directly from the sky and that subsequently removed or deposited by wind. Thus, the figures used here should be taken as approximations.
At the base of the mountains snowfall is much lower than above 10,000 ft (3,050 m), but individual storms can still bring impressive 24-hour totals. All of the lowland stations have had daily accumulations up to 20 in (60 cm). Snow cover in the lowlands is discontinuous, with durations rarely longer than six weeks. There is notably rapid disappearance of snow cover on the western slopes of the range, facing Owens Valley, up to elevations of 8,000–9,000 ft (2,440–2,745 m), even following major snowfalls. This slope faces a high angle of the sun during the relatively warm temperatures of afternoon. As expected, snow cover lasts longer on north- and east-facing slopes
than on south- or west-facing ones — often many weeks longer. In late spring and early summer, the snowline is distinctly lower and the cover more continuous in the mountains as viewed from Fish Lake Valley in the east than from Owens Valley in the west.
Precise measurements are nonexistent, but it is obvious that some snow is removed from its site of original fall on the extensive summit upland to slopes and canyons adjacent to the plateau. Because prevailing winds generally have a westerly component, the wind-blown snow is generally deposited on eastern slopes, although occasionally the direction is reversed, especially in conjunction with northeast winds following the passage of storms or with closed cyclones in late winter and spring. Quite probably, the sites of deepest snow accumulation in the White Mountains are at the heads of the major canyons on the east side of the range. Maximum Pleistocene glaciation occurred in these canyons, the heads of which are now steep-walled, east- or northeast-facing cirques — favorable locations for the accumulation and retention of snow. A conspicuous sight from Fish Lake Valley is a discontinuous, but commonly prominent, line of snow cornices at the edge of the summit plateau, commonly lasting through the summer months and sometimes well into fall or until the next season's snowpack begins. A worthwhile addition to the knowledge of the White-Inyo Range climate would be the acquisition of reliable data on how much snow is moved by wind and deposited either east or west of the summit upland. It may well be less than visual inspection, perhaps affected by the discomfort and poor visibility caused by fine blowing snow, indicates. Sporadic measurements of wind-blown snow in the Sierra Nevada in similar terrain do not substantiate the notion of a significant increase in snowpack in leeward sites, except in localized areas.