upslope

September 3, 2026 New England rain event — forecast vs. what fell

event hit rate 59% MAE 0.56″ 32 mountains scored

On September 3, 2026, 19 of 32 scored New England ski resorts recorded measurable rain, peaking at 0.84″ near Sunday River. upslope’s day-before forecasts verified at a 59% event hit rate with a mean absolute error of 0.56″ across 32 mountains. Ground truth: median of CoCoRaHS volunteer gauges near each resort (min 2 reporting).

Mountain by mountain

Resort	Forecast	Measured	Error	Call
Sunday RiverME	1.18″	0.84″	+0.34″	✓
Jay PeakVT	0.69″	0.8″	-0.11″	✓
BurkeVT	0.62″	0.61″	+0.01″	✓
Bretton WoodsNH	0.74″	0.59″	+0.15″	✓
WildcatNH	0.95″	0.59″	+0.36″	✓
Smugglers' NotchVT	0.62″	0.54″	+0.08″	✓
StoweVT	0.73″	0.51″	+0.22″	✓
LoonNH	0.97″	0.45″	+0.52″	✓
Waterville ValleyNH	1.11″	0.42″	+0.69″	✓
SaddlebackME	1.05″	0.41″	+0.64″	✓
SugarloafME	1.0″	0.41″	+0.59″	✓
Black MountainNH	1.06″	0.4″	+0.66″	✓
Bolton ValleyVT	0.74″	0.35″	+0.39″	✓
CannonNH	0.68″	0.34″	+0.34″	✓
AttitashNH	0.96″	0.33″	+0.63″	✓
CranmoreNH	0.91″	0.33″	+0.58″	✓
Mad River GlenVT	0.64″	0.24″	+0.4″	✓
GunstockNH	1.2″	0.17″	+1.03″	✓
SugarbushVT	0.6″	0.17″	+0.43″	✓
Pats PeakNH	0.89″	0.09″	+0.8″	✗
RaggedNH	1.19″	0.09″	+1.1″	✗
WachusettMA	0.46″	0.05″	+0.41″	✗
Berkshire EastMA	0.49″	0.04″	+0.45″	✗
CrotchedNH	0.66″	0.04″	+0.62″	✗
Mount SunapeeNH	0.93″	0.04″	+0.89″	✗
PicoVT	0.75″	0.03″	+0.72″	✗
BromleyVT	1.09″	0.02″	+1.07″	✗
KillingtonVT	0.8″	0.02″	+0.78″	✗
Magic MountainVT	0.78″	0.02″	+0.76″	✗
OkemoVT	0.53″	0.02″	+0.51″	✗
StrattonVT	0.85″	0.02″	+0.83″	✗
Mount SnowVT	0.87″	0.01″	+0.86″	✗

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