CAPITAL REGION — The season’s first significant Mohawk River ice jam formed Friday, but with temperatures set to drop in coming days, the near-term flood risk is likely minimal.
The ice jam, which formed just after midnight Friday, spurred Schenectady city and county officials to warn Stockade residents of potential flooding. The river level at Freeman’s Bridge on Friday neared flood stage, according to a National Weather Service hydrograph, but the water has since dropped to a safe level.
In coming days, the greater risk may be a snowstorm that is expected to hamper Tuesday’s evening commute and usher in frigid temperatures.
Forecasters are expecting a storm to drop 6 inches to a foot of snow – potentially more in some areas – across the Capital Region Tuesday before temperatures drop well below zero overnight Wednesday into Thursday.
While the roads may still be clear for the morning commute Tuesday, the drive home could be sloppy. Snowfall was expected to start Tuesday morning and intensify throughout the afternoon, continuing through the night. Forecasters warned conditions could make travel “very difficult to impossible” at times.
“The snow will be picking up intensity through the evening commute,” said Neil Stuart, a National Weather Service meteorologist.
On Monday afternoon the weather service posted a winter storm warning covering counties across the Capital Region; the warning goes into effect 1 a.m. Tuesday and lasts through 4 a.m. Wednesday.
Stuart said temperatures would plummet to “dangerously cold” levels overnight Wednesday into Thursday, with lows of around minus 5 and wind chills of around minus 20. He said the high temperature Thursday is unlikely to reach 10 degrees. Temperatures are expected to rise gradually Friday and through the weekend, with highs reaching the 20s by Saturday.
Watching the jam
When county and city officials warned Stockade residents of a flood risk on Friday, the river level registered at the weather service’s “action” level, but it started to fall before reaching flood stage.
Schenectady County spokesman Joe McQueen on Monday said there was no immediate flood risk and that county officials continued to monitor ice accumulation in the river.
“Right now, there is nothing imminent, but there is ice in the river, so it is something we are watching,” McQueen said.
John Garver, a Union College geologist who studies Mohawk River ice jams near Schenectady, said moderate temperatures, coupled with rain Thursday, caused a breakup of ice in the river. The ice jam is focused primarily in the narrow stretches through Rexford Knolls and just below lock 8 near Maalwyck Park in Glenville.
“[We get] all that rain on snow, and it goes,” he said of the ice breakup.
Garver said a network of river gauges and “jam cams” that monitor the river and its flood risks worked as intended, notifying researchers and emergency managers. He said the jams are likely to remain in place until temperatures hit the 40s or 50s and thaw the ice.
Garver cautioned that he does not predict or forecast flood risks directly, but he said the ice jam appeared to be stable as of Monday and did not pose an immediate flood risk.
“Water is going under the jams, so there is no immediate worry of them backing up water in a serious way,” Garver said.
Christoper Gazoorian, a USGS hydrologist and the federal point person on Mohawk River ice jam monitoring, agreed with Garver. He said now that an ice jam has formed, scientists and emergency managers will pay careful attention to the various factors that contribute to ice jam-related flooding. The big flood risk, Gazoorian and Garver said, comes if ice continues to build on the river before temperatures rise sharply and a river thaw pairs with heavy rainfall.
But it’s a waiting game until the ice starts to thaw, unlikely to happen this week given the frigid forecast.
“We have a lot of people watching it,” said Gazoorian, who had been furloughed for the past month because of the federal government shutdown. “Things change.”