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When the water equivalent of snow cannot be accurately measured by melting, weighing, or core sampling; the observer shall estimate the water equivalent to the nearest 0.01 inch. Use Figure 11-8 (New Snowfall to Estimated Meltwater Conversion Table) only as a guide in estimating the water equivalency of newly fallen snow.
Excerpt from Surface Weather Observing - FAA Order 7900.5B 5/11/01
| Meltwater Equivalent (Inches) | New Snowfall (Inches) | ||||||
|---|---|---|---|---|---|---|---|
| Temperature (°F) | |||||||
| 28° to 34° | 20° to 27° | 15° to 19° | 10° to 14° | 0° to 9° | -1° to -20° | -21° to -40° | |
| trace | trace | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 1.0 |
| .01 | 0.1 | 0.2 | 0.2 | 0.3 | 0.4 | 0.5 | 1.0 |
| .02 | 0.2 | 0.3 | 0.4 | 0.6 | 0.8 | 1.0 | 2.0 |
| .03 | 0.3 | 0.5 | 0.6 | 0.9 | 1.2 | 1.5 | 3.0 |
| .04 | 0.4 | 0.6 | 0.8 | 1.2 | 1.6 | 2.0 | 4.0 |
| .05 | 0.5 | 0.8 | 1.0 | 1.5 | 2.0 | 2.5 | 5.0 |
| .06 | 0.6 | 0.9 | 1.2 | 1.8 | 2.4 | 3.0 | 6.0 |
| .07 | 0.7 | 1.1 | 1.4 | 2.1 | 2.8 | 3.5 | 7.0 |
| .08 | 0.8 | 1.2 | 1.6 | 2.4 | 3.2 | 4.0 | 8.0 |
| .09 | 0.9 | 1.4 | 1.8 | 2.7 | 3.6 | 4.5 | 9.0 |
| .10 | 1.0 | 1.5 | 2.0 | 3.0 | 4.0 | 5.0 | 10.0 |
| .11 | 1.1 | 1.7 | 2.2 | 3.3 | 4.4 | 5.5 | 11.0 |
| .12 | 1.2 | 1.8 | 2.4 | 3.6 | 4.8 | 6.0 | 12.0 |
| .13 | 1.3 | 2.0 | 2.6 | 3.9 | 5.2 | 6.5 | 13.0 |
| .14 | 1.4 | 2.1 | 2.8 | 4.2 | 5.6 | 7.0 | 14.0 |
| .15 | 1.5 | 2.3 | 3.0 | 4.5 | 6.0 | 7.5 | 15.0 |
| .16 | 1.6 | 2.4 | 3.2 | 4.8 | 6.4 | 8.0 | 16.0 |
| .17 | 1.7 | 2.6 | 3.4 | 5.1 | 6.8 | 8.5 | 17.0 |
| .18 | 1.8 | 2.7 | 3.6 | 5.4 | 7.2 | 9.0 | 18.0 |
| .19 | 1.9 | 2.9 | 3.8 | 5.7 | 7.6 | 9.5 | 19.0 |
| .20 | 2.0 | 3.0 | 4.0 | 6.0 | 8.0 | 10.0 | 20.0 |
| .21 | 2.1 | 3.1 | 4.2 | 6.3 | 8.4 | 10.5 | 21.0 |
| .22 | 2.2 | 3.3 | 4.4 | 6.6 | 8.8 | 11.0 | 22.0 |
| .23 | 2.3 | 3.4 | 4.6 | 6.9 | 9.2 | 11.5 | 23.0 |
| .24 | 2.4 | 3.6 | 4.8 | 7.2 | 9.6 | 12.0 | 24.0 |
| .25 | 2.5 | 3.8 | 5.0 | 7.5 | 10.0 | 12.5 | 25.0 |
| .30 | 3.0 | 4.5 | 6.0 | 9.0 | 12.0 | 15.0 | 30.0 |
| .35 | 3.5 | 5.3 | 7.0 | 10.5 | 14.0 | 17.5 | 35.0 |
| .40 | 4.0 | 6.0 | 8.0 | 12.0 | 16.0 | 20.0 | 40.0 |
| .45 | 4.5 | 6.8 | 9.0 | 13.5 | 18.0 | 22.5 | 40.0 |
| .50 | 5.0 | 7.5 | 10.0 | 15.0 | 20.0 | 25.0 | 50.0 |
| .60 | 6.0 | 9.0 | 12.0 | 18.0 | 24.0 | 30.0 | 60.0 |
| .70 | 7.0 | 10.5 | 14.0 | 21.0 | 28.0 | 35.0 | 70.0 |
| .80 | 8.0 | 12.0 | 16.0 | 24.0 | 32.0 | 40.0 | 80.0 |
| .90 | 9.0 | 13.5 | 18.0 | 27.0 | 36.0 | 45.0 | 90.0 |
| 1.00 | 10.0 | 15.0 | 20.0 | 30.0 | 40.0 | 50.0 | 100.0 |
| 2.00 | 20.0 | 30.0 | 40.0 | 60.0 | 80.0 | 100.0 | 200.0 |
| 3.00 | 30.0 | 45.0 | 60.0 | 90.0 | 120.0 | 150.0 | 300.0 |
| This figure can only be used in determining amounts of newly fallen snow. It cannot be used for determining the water equivalency of "old" snow. Packing and melting/refreezing have substantial effects on the density of the snow pack and are not accounted for by this figure. | |||||||