Snow Briefing · Mountain pass
Donner Summit, CA
Mountain pass • I-80 • 7,051 ft • NBM 18Z 15 Nov 2026 • issued 19:39Z
The blend has 9.0″ of snow for Donner Summit over the next three days, 3.5″ of it in the first 24 hours, and 50.9″ over its ten days. Verdict: plow it twice.
The next ten days
Plow verdict on the 72-hour total: Plow it twice
| Horizon | Snow | Range 10–90% | Ice | Chance ≥1″ | Chance ≥6″ |
|---|---|---|---|---|---|
| Next 24 h | 3.5″ | 0.5–7.6″ | 0.01″ | 81% | 19% |
| Next 48 h | 5.1″ | 0.5–11.2″ | 0.01″ | 84% | 36% |
| Next 72 h | 9.0″ | — | 0.01″ | — | — |
| 5 days | 35.6″ | — | — | — | — |
| 7 days | 41.7″ | — | — | — | — |
| 10 days | 50.9″ | — | — | — | — |
Snow is the blend's deterministic forecast; the range is its 10th to 90th percentile and the chances are its own exceedance probabilities. Ice is freezing-rain accretion.
Day by day
| Climate day (12Z–12Z) | Snow | 90th pct | Chance ≥1″ | Chance ≥6″ |
|---|---|---|---|---|
| Tue 17 Nov | 4.5″ | 9.8″ | 83% | 29% |
| Wed 18 Nov | 0.2″ | — | — | — |
| Thu 19 Nov | 20.1″ | — | — | — |
| Fri 20 Nov | 9.3″ | — | — | — |
| Sat 21 Nov | 1.4″ | — | — | — |
| Sun 22 Nov | 4.3″ | — | — | — |
| Mon 23 Nov | 3.0″ | — | — | — |
| Tue 24 Nov | 0.9″ | — | — | — |
| Wed 25 Nov | 5.4″ | — | — | — |
Climate days run 12Z to 12Z, the window the NWS national snowfall analysis scores. Percentiles and chances are available for the first two days.
Two weeks out · ECMWF ensemble
| By | p10 | Median | p90 | Members ≥1″ | Members ≥6″ |
|---|---|---|---|---|---|
| Day 3 | 4.7″ | 7.0″ | 8.7″ | 100% | 70% |
| Day 5 | 16.0″ | 23.8″ | 32.1″ | 100% | 100% |
| Day 7 | 16.7″ | 25.2″ | 39.2″ | 100% | 100% |
| Day 10 | 20.0″ | 32.5″ | 52.7″ | 100% | 100% |
| Day 15 | 28.8″ | 46.8″ | 68.3″ | 100% | 100% |
ECMWF open data, 50 perturbed members at 0.25°, snow at a fixed 10:1 ratio, run 00Z 15 Nov. Cumulative from the run.
Density, level and trend
| Density at 48 h | 4.8 lb/ft³ |
| Load at 48 h | 2.0 lb/ft² |
| Snow-to-liquid ratio at 48 h | 13:1 |
| Snow level at 24 h / 48 h | 5,801 ft / — |
| Freezing rain chance, 48 h | 5% |
| Trend | up 0.3″ vs the previous run (48 h) |
How good is this forecast?
The blend's day-1 snowfall this season, scored against the NWS national snowfall analysis: mean absolute error 1.12″, bias −0.21″, critical success index at 6″ 0.06 over 71 scored days. Last scored day: 14 Nov 2026.
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forecastflakes.com/products/donner-summit-ca-pass · NWS National Blend of Models · ECMWF open data · © 2026 Forecast Flakes · not an official warning source