upslopeSeptember 10, 2026 New England rain event — forecast vs. what fell
event hit rate 91%
MAE 0.29″
32 mountains scored
On September 10, 2026, 31 of 32 scored New England ski resorts recorded measurable rain, peaking at 0.95″ near Killington. upslope’s day-before forecasts verified at a 91% event hit rate with a mean absolute error of 0.29″ across 32 mountains. Ground truth: median of CoCoRaHS volunteer gauges near each resort (min 2 reporting).
Mountain by mountain
| Resort | Forecast | Measured | Error | Call |
|---|---|---|---|---|
| KillingtonVT | 0.46″ | 0.95″ | -0.49″ | ✓ |
| OkemoVT | 0.18″ | 0.9″ | -0.72″ | ✓ |
| PicoVT | 0.42″ | 0.86″ | -0.44″ | ✓ |
| RaggedNH | 0.1″ | 0.84″ | -0.74″ | ✓ |
| Waterville ValleyNH | 0.44″ | 0.82″ | -0.38″ | ✓ |
| LoonNH | 0.43″ | 0.78″ | -0.35″ | ✓ |
| Mount SunapeeNH | 0.11″ | 0.73″ | -0.62″ | ✓ |
| BromleyVT | 0.25″ | 0.71″ | -0.46″ | ✓ |
| BurkeVT | 0.34″ | 0.71″ | -0.37″ | ✓ |
| StrattonVT | 0.2″ | 0.71″ | -0.51″ | ✓ |
| Jay PeakVT | 0.48″ | 0.69″ | -0.21″ | ✓ |
| Magic MountainVT | 0.11″ | 0.67″ | -0.56″ | ✓ |
| GunstockNH | 0.13″ | 0.65″ | -0.52″ | ✓ |
| Bolton ValleyVT | 0.47″ | 0.62″ | -0.15″ | ✓ |
| Smugglers' NotchVT | 0.48″ | 0.62″ | -0.14″ | ✓ |
| StoweVT | 0.54″ | 0.62″ | -0.08″ | ✓ |
| Mount SnowVT | 0.16″ | 0.56″ | -0.4″ | ✓ |
| Bretton WoodsNH | 0.34″ | 0.54″ | -0.2″ | ✓ |
| WildcatNH | 0.42″ | 0.54″ | -0.12″ | ✓ |
| SugarbushVT | 0.43″ | 0.51″ | -0.08″ | ✓ |
| Mad River GlenVT | 0.45″ | 0.48″ | -0.03″ | ✓ |
| Sunday RiverME | 0.19″ | 0.47″ | -0.28″ | ✓ |
| CannonNH | 0.49″ | 0.46″ | +0.03″ | ✓ |
| AttitashNH | 0.2″ | 0.42″ | -0.22″ | ✓ |
| CranmoreNH | 0.2″ | 0.4″ | -0.2″ | ✓ |
| Pats PeakNH | 0.07″ | 0.4″ | -0.33″ | ✗ |
| Black MountainNH | 0.26″ | 0.32″ | -0.06″ | ✓ |
| SaddlebackME | 0.3″ | 0.27″ | +0.03″ | ✓ |
| SugarloafME | 0.34″ | 0.27″ | +0.07″ | ✓ |
| Berkshire EastMA | 0.05″ | 0.23″ | -0.18″ | ✗ |
| CrotchedNH | 0.06″ | 0.14″ | -0.08″ | ✗ |
| WachusettMA | 0.02″ | 0.09″ | -0.07″ | ✓ |
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.