Flash Flood — Orleans, New York

2020-07-27 · near Gaines Basin, Orleans, New York

Event narrative

Ditches were overflowing and running across roads. In 3.5 hours, 5.10 inches of rainfall was reported.

Wider weather episode

A hot and very moist air mass was in place across the region with dewpoints in the 70s and precipitable water values approaching 2 inches. Diurnal instability along a lake breeze boundary allowed for convection to develop. The most notable thing about these boundaries was the intersection of the boundary off of Lake Erie with a weaker one south of Lake Ontario. Thunderstorms developed and trained along this intersection for hours. The net result was some of the heaviest rains our area has ever seen in such a short duration with amounts of between 7 and 8 inches reported in Orleans County.

View location on OpenStreetMap → (43.2600, -78.2200)

Source: NOAA Storm Events Database, event_id 912588. Narrative written by the NWS forecast office that issued the report.