A very rainy Vermont summer may get rainier yet.
The remnants of Tropical Storm Debby are expected to settle over most of the state on Friday, according to the latest forecast from the National Weather Service, soaking already saturated ground with slow, continuous precipitation.
Right now, the likeliest track for the heart of the storm is through northwestern Vermont, which could get somewhere between 2 and 4 inches of rain in a 12-18 hour period, according to Scott Whittier, a meteorologist at the weather service’s Burlington office.
That could cause “a lot of saturated soils-type flooding and areas of scattered flash flooding,” Whittier said, though he emphasized that uncertainty over Debby’s exact course means that it’s still “a fine line between potential flooding and no flooding, so we don’t want to go and cry wolf.”
Tropical Storm Debby is unleashing torrential downpours over South Carolina. Over the next two days, it is expected to track northward through Appalachia, before its remnants move into the Northeast on Friday morning, according to the forecast.
But “remnants” is just a term meteorologists use to describe when a storm has become post-tropical, according to Whittier, and by no means precludes the danger of severe weather. Tropical Storm Beryl’s remnants battered the state in early July, with floodwaters taking two lives and causing extensive damage.
And the Northeast Kingdom — parts of which received more than 8 inches of rain on July 29 and 30 — are particularly vulnerable to any more rain. Waterlogged soil, washed-out roads and damaged culverts in the area mean that “it might only require 2 inches” of rain to cause serious problems, according to Whittier.
“I would be more concerned about that area than any place else. They could see general flooding because the infrastructure is no longer there,” Whittier said.
Different computer models disagree about the precise path the storm will take, according to Whittier. Some have it passing through the Lower Connecticut River Valley, while others have it through the Adirondacks.
The weather service’s current prediction lies somewhere between the two, with the center of the storm moving north through the Champlain Valley into northwestern Vermont.
Whittier expects the rain will arrive “by daybreak on Friday. Then, getting heavier as we move into the afternoon. The heaviest would be Friday night into the earliest hours of Saturday.”
The slower pace of rainfall of Debby — relative to Beryl, where the bulk of the rain fell in 6 hours — means that flash flooding is less likely to occur. However, large parts of central and northeastern Vermont have extremely wet soil and rivers that are flowing above their normal streamflow, so they might struggle to absorb all the water, according to the weather service. This raises the danger of mainstem river flooding, according to Whittier.
“Rutland right now is possibly going to action or minor flood stage. The Winooski watershed is looking at either no flooding or action-stage. The Lamoille and Passumpsic rivers are going to be very close to flood stage but might not get there,” Whittier said.
Still, Whittier said there is some hope that Vermont may yet avoid the worst of Debby.
“When storms become post-tropical, the heaviest rains tend to be to the west of its path. That would be northern New York,” he said.
But regardless of whether the state emerges from Debby unscathed, the possibility of more tropical storms this summer looms over Whittier.
“Hurricane season hasn’t even peaked. We’ve got to stay vigilant. I certainly don’t like the trend,” he said.