Severe Localized Flash Flood Event, Warren County
A severe flash flood event unfolded over a portion of Warren county beginning during the mid afternoon on Monday June 13 when initially isolated thunderstorms formed due to terrain effects in a very hot and humid atmosphere. Temperatures hovered near 90° throughout the region on the 13th with dewpoint temperatures in the low 70s indicating a deeply tropical air mass in place, more typical of mid summer rather than early June. Also more typical of mid summer rather than early June was the weak steering flow present in the atmosphere. The weak winds aloft meant that any convection that formed would either remain over one location or train over the same locations producing torrential rains.
The t-storms were of a back-building multicell type that very effectively generated tremendous amounts of rainfall over a very localized part of Warren county, including Chestertown, Pottersville, Bolton Landing, and Warrensburg. Between five and six inches of rain fell in approximately three hours between 7:30pm and 10:30pm during the evening leading to extensive flooding in an areas that stretched from Bolton Landing to Chestertown. A WeatherNet 6 report from Bolton Landing indicated 5.57" of rain had fallen between 7:30pm and 10:30pm with approximately three inches in Pottersville. So much rain fell in such a short period of time that a culvert near Interstate 87 clogged causing a major flood of water and mud over the highway at exit 24, ultimately destroying both the north and south bound lanes forcing the highway to be closed between exits 23 and 25. In fact many roads including County Route 11 were severely damaged due to the flooding and closed as well. And more rain was yet to come.
The remnant circulation of what had once been the very early season tropical storm Arlene followed the initial round of t-storms that produced the initial severe flooding. Moderate to heavy rain re-developed over Warren county and much of the rest of eastern New York from the western Catskills to Schoharie county on north into the Mohawk valley and Adirondacks. Additional rainfall of one to three inches occurred between midnight and 6am on the 14th over the rain soaked Warren county which resulted in sustaining the flood conditions through the morning on Tuesday and sending the Schroon river out of its banks.
A state of emergency was declared in the towns of Bolton, Chester, Warrensburg, and Horicon with most roads being closed at the height of the widespread flooding. The most severe flooding was centered on the Bolton Landing area with power outages and especially water outages that lasted for several days. The Northway, I-87, between exits 23 and 25 remained closed for a full week as round the clock reconstruction of the highway took place.
Rainfall Reports From WeatherNet 6 spotters: Much of the reported rain fell in a period of approximately three hours and was extremely localized.