A very warm and humid air mass was in place across eastern New York on Tuesday, May 21st.  A slow moving frontal boundary was situated just north of the area across the Saint Lawrence River Valley along the United States-Canadian border.  During the day, a wave of low pressure moved along this boundary, allowing the boundary to slowly push southward towards the area.  With strong wind shear aloft and plenty of low level moisture in place, thunderstorms developed during the early afternoon hours.
Thunderstorms initially formed as single cells and supercells, but eventually organized into several broken lines, which moved from west to east across the area.  Many of these storms produced wind damage to trees and power lines. In addition, some thunderstorms produced hail, with hailstones as large as 2.50 inches in diameter across Columbia County.
As the surface wave of low pressure moved away and with the loss of daytime heating, thunderstorms eventually ended during the late evening hours.

Thunderstorm Wind in SARATOGA, NEW YORK
From 21-MAY-13 20:08:00 to 21-MAY-13 20:08:00 (EST-5)
Location: MOSHERVILLE
Magnitude: 50.00 EG
Reported by: Trained Spotter

Trees were reported down due to thunderstorm winds at the intersection of Route 147 and Route 29 in Kimball Corners.

Hail in COLUMBIA, NEW YORK
From 21-MAY-13 14:25:00 to 21-MAY-13 14:29:00 (EST-5)
Location: KINDERHOOK
Magnitude: 2.00 
Reported by: Trained Spotter

Several spotters reported hail ranging from one to two inches in diameter fell in Kinderhook.

Hail in RENSSELAER, NEW YORK
From 21-MAY-13 14:30:00 to 21-MAY-13 14:32:00 (EST-5)
Location: EASTMOR
Magnitude: 1.00 
Reported by: Trained Spotter

A trained spotter reported quarter size hail fell from a thunderstorm one mile east of North Greenbush.

Hail in ALBANY, NEW YORK
From 21-MAY-13 14:07:00 to 21-MAY-13 14:09:00 (EST-5)
Location: DELMAR
Magnitude: 0.88 
Reported by: Amateur Radio

Nickel size hail was reported over Amateur Radio from a thunderstorm in Delmar.

Hail in ALBANY, NEW YORK
From 21-MAY-13 14:15:00 to 21-MAY-13 14:17:00 (EST-5)
Location: ALBANY
Magnitude: 1.00 
Reported by: Public

A member of the public reported quarter size hail fell in the South End section of Albany.

Hail in SARATOGA, NEW YORK
From 21-MAY-13 20:35:00 to 21-MAY-13 20:36:00 (EST-5)
Location: SARATOGA SPGS
Magnitude: 0.75 
Reported by: Public

A member of the public reported penny size hail from a thunderstorm in Saratoga Springs.

Thunderstorm Wind in RENSSELAER, NEW YORK
From 21-MAY-13 20:55:00 to 21-MAY-13 20:55:00 (EST-5)
Location: HOOSICK
Magnitude: 50.00 EG
Reported by: Trained Spotter

A tree was reported down due to thunderstorm winds on Route 7 in Hoosick Falls.

Thunderstorm Wind in HERKIMER, NEW YORK
From 21-MAY-13 19:03:00 to 21-MAY-13 19:03:00 (EST-5)
Location: FRANKFORT CENTER
Magnitude: 50.00 EG
Reported by: Trained Spotter

Two trees were reported down and across Center Road due to thunderstorm winds in Frankfort Center.

Hail in HERKIMER, NEW YORK
From 21-MAY-13 16:15:00 to 21-MAY-13 16:25:00 (EST-5)
Location: GOODELL CORNERS
Magnitude: 1.50 
Reported by: Trained Spotter

A trained spotter reported half dollar to ping pong ball size hail from a thunderstorm two miles southeast of Fairfield.

Hail in HERKIMER, NEW YORK
From 21-MAY-13 16:20:00 to 21-MAY-13 16:22:00 (EST-5)
Location: DOLGEVILLE
Magnitude: 0.75 
Reported by: Trained Spotter

A trained spotter reported penny size hail from a thunderstorm covering a road in Dolgeville.

Thunderstorm Wind in SARATOGA, NEW YORK
From 21-MAY-13 20:10:00 to 21-MAY-13 20:10:00 (EST-5)
Location: PARKIS MILLS
Magnitude: 50.00 EG
Reported by: Trained Spotter

A tree was reported down and on wires due to thunderstorm winds on Parkis Hills Road at Graves Road in Galway.

Thunderstorm Wind in MONTGOMERY, NEW YORK
From 21-MAY-13 20:15:00 to 21-MAY-13 20:15:00 (EST-5)
Location: AMSTERDAM
Magnitude: 50.00 EG
Reported by: 911 Call Center

A tree was down and on a residence as a result of thunderstorm winds in Amsterdam.

Hail in COLUMBIA, NEW YORK
From 21-MAY-13 14:28:00 to 21-MAY-13 14:42:00 (EST-5)
Location: GHENT
Magnitude: 2.50 
Reported by: Trained Spotter

Amateur radio, trained spotters and members of the public reported hail of 1.00 to 2.50 inches in diameter fell from a thunderstorm in Ghent.

Thunderstorm Wind in FULTON, NEW YORK
From 21-MAY-13 19:50:00 to 21-MAY-13 19:50:00 (EST-5)
Location: GLOVERSVILLE
Magnitude: 50.00 EG
Reported by: Amateur Radio

A tree was reported down and on a house due to thunderstorm winds in Gloversville.

Hail in SARATOGA, NEW YORK
From 21-MAY-13 20:20:00 to 21-MAY-13 20:22:00 (EST-5)
Location: GALWAY
Magnitude: 1.00 
Reported by: Trained Spotter

A meteorologist reported quarter size hail from a thunderstorm in Galway.

Hail in RENSSELAER, NEW YORK
From 21-MAY-13 14:17:00 to 21-MAY-13 14:17:00 (EST-5)
Location: CLINTON PARK
Magnitude: 1.00 
Reported by: Amateur Radio

Amateur radio reported quarter size hail fell in Rensselaer, which covered the ground.

Hail in COLUMBIA, NEW YORK
From 21-MAY-13 14:19:00 to 21-MAY-13 14:21:00 (EST-5)
Location: STUYVESANT FALLS
Magnitude: 1.00 
Reported by: Amateur Radio

Amateur radio reported quarter size hail fell from a thunderstorm in Stuyvesant Falls.

Thunderstorm Wind in COLUMBIA, NEW YORK
From 21-MAY-13 16:00:00 to 21-MAY-13 16:00:00 (EST-5)
Location: PUMPKIN HOLLOW
Magnitude: 60.00 EG
Reported by: Public

A member of the public reported damage to trees as a result of thunderstorm winds.  Many large limbs and branches were down, including limbs of 50 foot tall trees.

Thunderstorm Wind in COLUMBIA, NEW YORK
From 21-MAY-13 16:15:00 to 21-MAY-13 16:15:00 (EST-5)
Location: COPAKE
Magnitude: 50.00 EG
Reported by: County Official

Trees and multiple power lines were reported down on Main Street (Route 7A) due to thunderstorm winds in Copake.

Hail in COLUMBIA, NEW YORK
From 21-MAY-13 17:25:00 to 21-MAY-13 17:30:00 (EST-5)
Location: ANCRAM
Magnitude: 1.75 
Reported by: Trained Spotter

A trained spotter reported ping pong ball to golf ball size hail in Ancramdale.

Hail in COLUMBIA, NEW YORK
From 21-MAY-13 14:30:00 to 21-MAY-13 14:32:00 (EST-5)
Location: VALATIE
Magnitude: 2.00 
Reported by: Public

A member of the public reported hail of 2.00 inches in diameter fell from a thunderstorm in Valatie.

Hail in COLUMBIA, NEW YORK
From 21-MAY-13 14:39:00 to 21-MAY-13 14:42:00 (EST-5)
Location: CHATHAM
Magnitude: 1.25 
Reported by: Trained Spotter

A spotter reported half dollar size hail fell from a thunderstorm in Chatham.

Hail in RENSSELAER, NEW YORK
From 21-MAY-13 14:20:00 to 21-MAY-13 14:22:00 (EST-5)
Location: CLINTON HGTS
Magnitude: 1.00 
Reported by: Social Media

A member of the public reported via Facebook that quarter size hail fell from a thunderstorm in Hampton Manner.

Hail in RENSSELAER, NEW YORK
From 21-MAY-13 14:23:00 to 21-MAY-13 14:25:00 (EST-5)
Location: SHERWOOD PARK
Magnitude: 1.00 
Reported by: Trained Spotter

A Skywarn spotter reported quarter size hail fell from a thunderstorm in East Greenbush.

Thunderstorm Wind in HERKIMER, NEW YORK
From 21-MAY-13 19:05:00 to 21-MAY-13 19:05:00 (EST-5)
Location: EAST SCHUYLER
Magnitude: 50.00 EG
Reported by: 911 Call Center

Trees and wires were reported down due to thunderstorm winds in Frankfort.

Thunderstorm Wind in HERKIMER, NEW YORK
From 21-MAY-13 19:30:00 to 21-MAY-13 19:30:00 (EST-5)
Location: DOLGEVILLE
Magnitude: 50.00 EG
Reported by: 911 Call Center

Numerous trees and wires were reported down due to thunderstorm winds in Dolgeville.

Hail in HAMILTON, NEW YORK
From 21-MAY-13 19:35:00 to 21-MAY-13 19:38:00 (EST-5)
Location: WELLS
Magnitude: 1.50 
Reported by: Broadcast Media

Local media reported ping pong ball size hail from a thunderstorm in Wells.

Hail in HERKIMER, NEW YORK
From 21-MAY-13 15:55:00 to 21-MAY-13 16:00:00 (EST-5)
Location: MOHAWK
Magnitude: 1.00 
Reported by: Social Media

The public via Facebook reported quarter size hail from a thunderstorm in Mohawk.

Thunderstorm Wind in FULTON, NEW YORK
From 21-MAY-13 19:35:00 to 21-MAY-13 19:35:00 (EST-5)
Location: OPPENHEIM
Magnitude: 50.00 EG
Reported by: 911 Call Center

Trees and wires were reported down from thunderstorm winds in Oppenheim.

Hail in RENSSELAER, NEW YORK
From 21-MAY-13 14:42:00 to 21-MAY-13 14:44:00 (EST-5)
Location: WEST SAND LAKE
Magnitude: 0.75 
Reported by: Public

A member of the public reported penny size hail fell from a thunderstorm in West Sand Lake.

Hail in COLUMBIA, NEW YORK
From 21-MAY-13 15:45:00 to 21-MAY-13 15:54:00 (EST-5)
Location: TAGHKANIC
Magnitude: 1.00 
Reported by: Trained Spotter

A trained spotter reported quarter size hail from a thunderstorm in Taghkanic.

Thunderstorm Wind in COLUMBIA, NEW YORK
From 21-MAY-13 15:45:00 to 21-MAY-13 15:45:00 (EST-5)
Location: GHENT
Magnitude: 50.00 EG
Reported by: County Official

Multiple trees were reported down from thunderstorm winds in Ghent.

Hail in HERKIMER, NEW YORK
From 21-MAY-13 15:56:00 to 21-MAY-13 16:00:00 (EST-5)
Location: EAST HERKIMER
Magnitude: 1.00 
Reported by: Post Office

A U.S. Postal Employee reported quarter size hail from a thunderstorm in Herkimer.

Hail in HERKIMER, NEW YORK
From 21-MAY-13 16:15:00 to 21-MAY-13 16:25:00 (EST-5)
Location: FAIRFIELD
Magnitude: 1.00 
Reported by: Trained Spotter

A trained spotter reported quarter size hail from a thunderstorm in Fairfield.

Hail in HAMILTON, NEW YORK
From 21-MAY-13 19:11:00 to 21-MAY-13 19:14:00 (EST-5)
Location: HIGGINS BAY
Magnitude: 1.50 
Reported by: Trained Spotter

A local media weather spotter reported ping pong ball size hail from a thunderstorm in Piseco.

Thunderstorm Wind in HERKIMER, NEW YORK
From 21-MAY-13 19:00:00 to 21-MAY-13 19:00:00 (EST-5)
Location: FRANKFORT HILL
Magnitude: 50.00 EG
Reported by: Trained Spotter

Multiple trees were reported down due to thunderstorm winds at Frankfort Hill.