upslopeSeptember 6, 2026 New England rain event — forecast vs. what fell
event hit rate 28%
MAE 0.18″
32 mountains scored
On September 6, 2026, 23 of 32 scored New England ski resorts recorded measurable rain, peaking at 0.54″ near Wachusett. upslope’s day-before forecasts verified at a 28% event hit rate with a mean absolute error of 0.18″ across 32 mountains. Ground truth: median of CoCoRaHS volunteer gauges near each resort (min 2 reporting).
Mountain by mountain
| Resort | Forecast | Measured | Error | Call |
|---|---|---|---|---|
| WachusettMA | 0.08″ | 0.54″ | -0.46″ | ✗ |
| LoonNH | 0.02″ | 0.51″ | -0.49″ | ✗ |
| Waterville ValleyNH | 0.02″ | 0.5″ | -0.48″ | ✗ |
| Mount SunapeeNH | 0.07″ | 0.45″ | -0.38″ | ✗ |
| Sunday RiverME | 0.01″ | 0.45″ | -0.44″ | ✗ |
| CannonNH | 0.02″ | 0.4″ | -0.38″ | ✗ |
| RaggedNH | 0.07″ | 0.4″ | -0.33″ | ✗ |
| GunstockNH | 0.01″ | 0.25″ | -0.24″ | ✗ |
| Berkshire EastMA | 0.03″ | 0.24″ | -0.21″ | ✗ |
| CrotchedNH | 0.07″ | 0.24″ | -0.17″ | ✗ |
| Bretton WoodsNH | 0.01″ | 0.22″ | -0.21″ | ✗ |
| Magic MountainVT | 0.01″ | 0.22″ | -0.21″ | ✗ |
| SugarbushVT | 0.02″ | 0.22″ | -0.2″ | ✗ |
| Pats PeakNH | 0.09″ | 0.21″ | -0.12″ | ✗ |
| WildcatNH | 0.02″ | 0.21″ | -0.19″ | ✗ |
| Black MountainNH | 0.01″ | 0.18″ | -0.17″ | ✗ |
| OkemoVT | 0.02″ | 0.17″ | -0.15″ | ✗ |
| AttitashNH | 0.02″ | 0.13″ | -0.11″ | ✗ |
| CranmoreNH | 0.01″ | 0.13″ | -0.12″ | ✗ |
| Jay PeakVT | 0.01″ | 0.13″ | -0.12″ | ✗ |
| Mad River GlenVT | 0.03″ | 0.13″ | -0.1″ | ✗ |
| BurkeVT | — | 0.12″ | -0.12″ | ✗ |
| Bolton ValleyVT | 0.01″ | 0.1″ | -0.09″ | ✗ |
| StoweVT | 0.01″ | 0.09″ | -0.08″ | ✓ |
| BromleyVT | 0.02″ | 0.08″ | -0.06″ | ✓ |
| Mount SnowVT | — | 0.08″ | -0.08″ | ✓ |
| KillingtonVT | 0.02″ | 0.06″ | -0.04″ | ✓ |
| Smugglers' NotchVT | 0.02″ | 0.06″ | -0.04″ | ✓ |
| PicoVT | 0.02″ | 0.05″ | -0.03″ | ✓ |
| StrattonVT | 0.01″ | 0.05″ | -0.04″ | ✓ |
| SaddlebackME | 0.01″ | 0.04″ | -0.03″ | ✓ |
| SugarloafME | 0.01″ | 0.04″ | -0.03″ | ✓ |
Scoring fix, Oct 8, 2026: earlier versions compared each gauge report (7am-to-7am) against the forecast for the wrong calendar day; all history was rescored under the corrected rule.
Forecast = upslope's NWS-based rain forecast for the same 7am-to-7am window the gauges measure, from the last run before that window opened. ✓ = correctly called rain above/below 0.1″. Positive error = over-forecast.