Several mid-atmospheric impulses traveled along a stationary boundary across northern New York during the early afternoon and evening hours of July 18th. This stationary boundary separated warm, humid air across much of New York from cooler, drier air across the international border with Canada.
The first round of thunderstorms developed during the early afternoon along the Canadian-northern New York border in northern Franklin county and moved across Clinton county toward Vermont. Numerous reports of downed trees and power lines between Chateaugay (Franklin county) and Chazy (Clinton county).
A second round of severe thunderstorms moved across St. Lawrence and northern Franklin counties during the evening. Numerous reports of downed trees causing downed power lines and some structural damage in the Norfolk, Norwood region as well as affecting the Malone (Franklin county) area.

Thunderstorm Wind in FRANKLIN, NEW YORK
From 18-JUL-08 13:25:00 to 18-JUL-08 13:25:00 (EST-5)
Location: CHATEAUGAY
Magnitude: 50.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Post Office

Trees and branches downed by thunderstorm winds in Chateaugay.

Thunderstorm Wind in CLINTON, NEW YORK
From 18-JUL-08 13:30:00 to 18-JUL-08 13:30:00 (EST-5)
Location: ELLENBURG CENTER
Magnitude: 50.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

Trees reported down and blocking intersection of Route 11 and Brandy Brook road.

Thunderstorm Wind in CLINTON, NEW YORK
From 18-JUL-08 14:00:00 to 18-JUL-08 14:00:00 (EST-5)
Location: CHAZY
Magnitude: 60.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Numerous reports of widespread tree damage throughout Chazy. Specifically hit hard locations include Miner Farm, Olena and Ridge roads with fallen trees on power lines, homes and vehicles.

Hail in ST. LAWRENCE, NEW YORK
From 18-JUL-08 14:15:00 to 18-JUL-08 14:15:00 (EST-5)
Location: MASSENA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Quarter size hail reported just east of Massena along Route 37.

Hail in FRANKLIN, NEW YORK
From 18-JUL-08 14:50:00 to 18-JUL-08 14:50:00 (EST-5)
Location: MALONE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Post Office

Nickel size hail reported in Malone.

Thunderstorm Wind in CLINTON, NEW YORK
From 18-JUL-08 14:48:00 to 18-JUL-08 14:48:00 (EST-5)
Location: SCHUYLER FALLS
Magnitude: 50.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Public

Several reports of trees down in Schuyler Falls.

Thunderstorm Wind in ST. LAWRENCE, NEW YORK
From 18-JUL-08 17:42:00 to 18-JUL-08 17:42:00 (EST-5)
Location: WADDINGTON
Magnitude: 55.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Reports of numerous trees and power lines downed by thunderstorm winds which have caused blocked and closed roads.

Thunderstorm Wind in FRANKLIN, NEW YORK
From 18-JUL-08 18:55:00 to 18-JUL-08 19:05:00 (EST-5)
Location: MALONE
Magnitude: 55.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Numerous trees and power lines downed by thunderstorm winds in the Moria, Brushton, Bangor and Malone area.

Thunderstorm Wind in ST. LAWRENCE, NEW YORK
From 18-JUL-08 18:05:00 to 18-JUL-08 18:15:00 (EST-5)
Location: NORFOLK
Magnitude: 60.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Numerous trees and power lines down across Norwood, Norfolk and North Stockholm. Several large 100-150 year old maple and oak trees fallen onto vehicles, homes and other structures.