upslopeSeptember 21, 2026 New England rain event — forecast vs. what fell
event hit rate 100%
MAE 0.17″
32 mountains scored
On September 21, 2026, 30 of 32 scored New England ski resorts recorded measurable rain, peaking at 0.73″ near Berkshire East. upslope’s day-before forecasts verified at a 100% event hit rate with a mean absolute error of 0.17″ across 32 mountains. Ground truth: median of CoCoRaHS volunteer gauges near each resort (min 2 reporting).
Mountain by mountain
| Resort | Forecast | Measured | Error | Call |
|---|---|---|---|---|
| Berkshire EastMA | 0.36″ | 0.73″ | -0.37″ | ✓ |
| Bretton WoodsNH | 0.14″ | 0.54″ | -0.4″ | ✓ |
| Pats PeakNH | 0.21″ | 0.48″ | -0.27″ | ✓ |
| RaggedNH | 0.17″ | 0.48″ | -0.31″ | ✓ |
| Sunday RiverME | 0.1″ | 0.47″ | -0.37″ | ✓ |
| Black MountainNH | 0.14″ | 0.46″ | -0.32″ | ✓ |
| LoonNH | 0.17″ | 0.46″ | -0.29″ | ✓ |
| Magic MountainVT | 0.3″ | 0.46″ | -0.16″ | ✓ |
| Mount SunapeeNH | 0.19″ | 0.46″ | -0.27″ | ✓ |
| WildcatNH | 0.16″ | 0.46″ | -0.3″ | ✓ |
| GunstockNH | 0.2″ | 0.45″ | -0.25″ | ✓ |
| Waterville ValleyNH | 0.19″ | 0.44″ | -0.25″ | ✓ |
| AttitashNH | 0.14″ | 0.43″ | -0.29″ | ✓ |
| CranmoreNH | 0.12″ | 0.43″ | -0.31″ | ✓ |
| WachusettMA | 0.33″ | 0.43″ | -0.1″ | ✓ |
| CrotchedNH | 0.2″ | 0.42″ | -0.22″ | ✓ |
| OkemoVT | 0.2″ | 0.42″ | -0.22″ | ✓ |
| BromleyVT | 0.4″ | 0.4″ | 0.0″ | ✓ |
| StrattonVT | 0.35″ | 0.4″ | -0.05″ | ✓ |
| CannonNH | 0.17″ | 0.38″ | -0.21″ | ✓ |
| Mount SnowVT | 0.3″ | 0.38″ | -0.08″ | ✓ |
| SugarbushVT | 0.26″ | 0.3″ | -0.04″ | ✓ |
| KillingtonVT | 0.23″ | 0.28″ | -0.05″ | ✓ |
| PicoVT | 0.24″ | 0.28″ | -0.04″ | ✓ |
| Mad River GlenVT | 0.24″ | 0.27″ | -0.03″ | ✓ |
| Bolton ValleyVT | 0.22″ | 0.21″ | +0.01″ | ✓ |
| BurkeVT | 0.13″ | 0.15″ | -0.02″ | ✓ |
| Jay PeakVT | 0.11″ | 0.15″ | -0.04″ | ✓ |
| StoweVT | 0.18″ | 0.15″ | +0.03″ | ✓ |
| Smugglers' NotchVT | 0.17″ | 0.13″ | +0.04″ | ✓ |
| SaddlebackME | 0.07″ | 0.09″ | -0.02″ | ✓ |
| SugarloafME | 0.05″ | 0.09″ | -0.04″ | ✓ |
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.