Heavy Rain Event (Former Hurricane Frances Related)
Heavy rain developed across the region late Wednesday afternoon, September 8 and continued through early Thursday morning, September 9. The rainfall was loosely related to the remnant circulation of what was once powerful Hurricane Frances. The remnants of Frances, Wednesday afternoon, tracked north along the western slopes of the Appalachians, bringing with it a deep tropical air mass up along the eastern seaboard. The tropical air mass encountered a stalled frontal system over southeast New York and southern New England. The air north of the stalled front was characterized by lower dewpoints and cooler temperatures and was thus more dense than the tropical air flowing north. As the tropical air encountered the front it was forced to rise up and over the dense air north of the boundary, a process called overrunning. The overrunning process allowed heavy rain to develop along and north of the boundary which continued through the night. The heaviest rain with the system was associated directly with the remnants of Frances, which tracked into western New York producing widespread rainfall amounts of 3"-6" and significant flooding near and around Buffalo. Rainfall through early Thursday morning across eastern New York and western New England was more variable due partly to terrain influences, but generally averaged 3/4" to 1.5" with some localized amounts in excess of 3" in upslope areas of the Catskills and the hills in western New England and the Adirondacks.
As the remnants of Frances lifted north through western New York through the day Thursday, it forced the stalled front to move north as well allowing the tropical air mass to infiltrate all of eastern New York and western New England. Dewpoints climbed to between 70 and 75 degrees and breaks of sunshine developed. The sunshine destabilized the atmosphere enough, as temperatures climbed to around 80 degrees, to allow bands of torrential rains and scattered thunderstorms to form through the afternoon and the evening. Additional localized rainfall amounts ranged from 1"-2" with some of the tropical downpours in the region.
The cold front passed into western New England between 8:00pm and 9:00pm on Thursday bringing one final found of downpours to areas along and east of the Hudson river and a burst of wind gusts in excess of 30 mph. With the passage of the front, rain moved out of the region prior to midnight.
Rainfall totals from Wednesday September 8-Thursday afternoon September 9, 2004 (Hurricane Frances Related Event)
(Note: These rainfall totals are through 5:00pm September 9 and do not include any additional rainfall that occurred with the passage of the cold front between 5:01pm and midnight, unless otherwise marked as "Total")