upslope

September 21, 2026 New England rain event — forecast vs. what fell

event hit rate 19% MAE 0.33″ 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 19% event hit rate with a mean absolute error of 0.33″ 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 EastMA0.04″0.73″-0.69″✗
Bretton WoodsNH0.03″0.54″-0.51″✗
Pats PeakNH0.12″0.48″-0.36″✓
RaggedNH0.08″0.48″-0.4″✗
Sunday RiverME0.03″0.47″-0.44″✗
Black MountainNH0.03″0.46″-0.43″✗
LoonNH0.03″0.46″-0.43″✗
Magic MountainVT0.01″0.46″-0.45″✗
Mount SunapeeNH0.08″0.46″-0.38″✗
WildcatNH0.03″0.46″-0.43″✗
GunstockNH0.1″0.45″-0.35″✓
Waterville ValleyNH0.04″0.44″-0.4″✗
AttitashNH0.04″0.43″-0.39″✗
CranmoreNH0.03″0.43″-0.4″✗
WachusettMA0.18″0.43″-0.25″✓
CrotchedNH0.15″0.42″-0.27″✓
OkemoVT0.01″0.42″-0.41″✗
BromleyVT0.01″0.4″-0.39″✗
StrattonVT0.01″0.4″-0.39″✗
CannonNH0.03″0.38″-0.35″✗
Mount SnowVT0.01″0.38″-0.37″✗
SugarbushVT—0.3″-0.3″✗
KillingtonVT0.01″0.28″-0.27″✗
PicoVT—0.28″-0.28″✗
Mad River GlenVT—0.27″-0.27″✗
Bolton ValleyVT—0.21″-0.21″✗
BurkeVT0.01″0.15″-0.14″✗
Jay PeakVT—0.15″-0.15″✗
StoweVT—0.15″-0.15″✗
Smugglers' NotchVT—0.13″-0.13″✗
SaddlebackME0.02″0.09″-0.07″✓
SugarloafME0.02″0.09″-0.07″✓

Forecast = upslope's last published NWS-based rain number the day before. ✓ = correctly called rain above/below 0.1″. Positive error = over-forecast.