upslopeSeptember 18, 2026 New England rain event — forecast vs. what fell
event hit rate 75%
MAE 0.28″
32 mountains scored
On September 18, 2026, 25 of 32 scored New England ski resorts recorded measurable rain, peaking at 1.21″ near Pats Peak. upslope’s day-before forecasts verified at a 75% event hit rate with a mean absolute error of 0.28″ across 32 mountains. Ground truth: median of CoCoRaHS volunteer gauges near each resort (min 2 reporting).
Mountain by mountain
| Resort | Forecast | Measured | Error | Call |
|---|---|---|---|---|
| Pats PeakNH | 0.2″ | 1.21″ | -1.01″ | ✓ |
| RaggedNH | 0.14″ | 1.1″ | -0.96″ | ✓ |
| Mount SunapeeNH | 0.23″ | 1.07″ | -0.84″ | ✓ |
| GunstockNH | 0.16″ | 0.9″ | -0.74″ | ✓ |
| CrotchedNH | 0.22″ | 0.81″ | -0.59″ | ✓ |
| PicoVT | 0.11″ | 0.75″ | -0.64″ | ✓ |
| StrattonVT | 0.17″ | 0.75″ | -0.58″ | ✓ |
| BromleyVT | 0.18″ | 0.72″ | -0.54″ | ✓ |
| Magic MountainVT | 0.18″ | 0.71″ | -0.53″ | ✓ |
| OkemoVT | 0.15″ | 0.71″ | -0.56″ | ✓ |
| KillingtonVT | 0.12″ | 0.65″ | -0.53″ | ✓ |
| Mount SnowVT | 0.18″ | 0.37″ | -0.19″ | ✓ |
| Berkshire EastMA | 0.21″ | 0.27″ | -0.06″ | ✓ |
| LoonNH | 0.1″ | 0.2″ | -0.1″ | ✓ |
| Black MountainNH | 0.07″ | 0.18″ | -0.11″ | ✗ |
| WildcatNH | 0.05″ | 0.18″ | -0.13″ | ✗ |
| AttitashNH | 0.08″ | 0.17″ | -0.09″ | ✗ |
| CranmoreNH | 0.1″ | 0.17″ | -0.07″ | ✓ |
| Sunday RiverME | 0.04″ | 0.16″ | -0.12″ | ✗ |
| SaddlebackME | 0.02″ | 0.15″ | -0.13″ | ✗ |
| SugarloafME | 0.01″ | 0.15″ | -0.14″ | ✗ |
| Waterville ValleyNH | 0.11″ | 0.15″ | -0.04″ | ✓ |
| Bretton WoodsNH | 0.08″ | 0.14″ | -0.06″ | ✗ |
| CannonNH | 0.09″ | 0.12″ | -0.03″ | ✗ |
| WachusettMA | 0.15″ | 0.1″ | +0.05″ | ✓ |
| Jay PeakVT | — | 0.04″ | -0.04″ | ✓ |
| SugarbushVT | 0.03″ | 0.04″ | -0.01″ | ✓ |
| BurkeVT | 0.02″ | 0.03″ | -0.01″ | ✓ |
| Mad River GlenVT | 0.02″ | 0.03″ | -0.01″ | ✓ |
| Bolton ValleyVT | — | 0.02″ | -0.02″ | ✓ |
| Smugglers' NotchVT | — | 0.02″ | -0.02″ | ✓ |
| StoweVT | — | 0.02″ | -0.02″ | ✓ |
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.