The ground across central New York had been soaking for hours by the time Wednesday evening turned dangerous. By mid-morning on September 2, one to two inches of rain had already fallen across Onondaga County — the region home to Syracuse — in under three hours, flooding roads in Camillus, Solvay, and surrounding communities and triggering flash flood warnings that closed underpasses, swamped low-lying streets, and overwhelmed creeks across Baldwinsville, Cicero, Lysander, and Liverpool. None of that water had absorbed into the already-saturated soil by the time a second, stronger storm line arrived after 7:30 p.m. — and by 8:41 p.m., Doppler radar had detected rotation in a storm cell moving over Union Springs near Auburn, prompting a tornado warning for Cayuga County that reached communities dealing with flooded roads since morning.
That overlap — flooded roads still impassable from the dawn storms while tornado shelter orders were arriving on phones — is what made the September 2 event in central New York and northeastern Pennsylvania more hazardous than either threat would have been on its own. The National Weather Service offices in Binghamton, Buffalo, and State College, Pennsylvania issued dozens of overlapping warnings across two states throughout the day and into the early hours of Thursday morning, leaving more than 20 counties under flood watches and tornado watches simultaneously at the evening’s peak. Across Pennsylvania, Delaware, and New Jersey, more than 65,000 customers were already without power before Wednesday’s worst storms even arrived, according to the FOX Forecast Center — with that number expected to grow as the most dangerous phase of the rare multiday Northeast storm pattern moved through.
Why Flooded Ground at Dawn Made Evening Tornado Warnings Far More Dangerous
The mechanism that made Wednesday’s compounding crises amplify each other is called training thunderstorms — a meteorological pattern in which storm cells repeatedly track one path, like cars on a railroad track, with each successive cell finding no dry ground to absorb its rainfall. The NWS Binghamton office identified this dynamic explicitly in its afternoon Flood Watch bulletin, warning that “several inches of rain already on the ground would be combined with an additional one to three inches or more through early Thursday morning” and that training thunderstorms would enhance the threat for excessive runoff and flash flooding across the region.
This is why the morning flooding was not just an unfortunate preamble to Wednesday’s evening events — it was their amplifier. Soil that shed one to two inches of rain before noon has no capacity to absorb additional rainfall. Every subsequent raindrop that lands on already-saturated ground becomes surface runoff immediately, with no delay to percolation. Flash flooding that might require three or four inches of rainfall on dry soil can develop in a single inch on soil that is already at capacity. The FOX Forecast Center confirmed that Wednesday’s storms were producing rain rates of up to two inches per hour across central New York and Pennsylvania, with storm totals exceeding three inches in some locations…