Weather officials say expected warm temperatures and periods of rain could cause flood conditions this week in the Capital Region.
The National Weather Service in Albany on Wednesday issued a flood watch for eastern New York, western Massachusetts, southern Vermont and northwestern Connecticut.
The watch goes into effect late Thursday and will run through Saturday afternoon. Local residents who worried about bitter cold temperatures last weekend will have to worry about possible flooding on Friday and icy road conditions Saturday.
People may not have to worry about the wintry mix that hit the area Wednesday night. Temperatures will climb above 40 by Thursday afternoon; forecasters say it will the warmest day since before Christmas.
On Friday, temperatures in the low to mid-50s are probable.
The trouble will start Thursday night, when rain moves into the area. Rain will gradually change to sleet and freezing rain late Friday night.
"With that rainfall, and with a strong southerly wind, temperatures won't be dropping at all," said Brian Montgomery, a meteorologist with the weather service. "In fact, they're probably going to be rising Thursday night with periods of moderate to heavy rainfall."
The warmer temperatures and rainfall may move ice around in local streams and rivers.
"Any ice we have currently out there may begin to move a bit and with that movement could result in an ice jam, flooding bridges, overpasses and especially in Schenectady, around the Stockade area," Montgomery said. "With the unique turn of the Mohawk River basin, that could result in some challenges with some water backing up."
Jams occur when ice floating downstream hits a barrier or a bend and gets stuck. Water can't get through and must go around the jam — and over river or stream banks.
The Mohawk River is on the service's list of trouble spots. Weather officials say ice jams often form at Tribes Hill, upstream of Lock 12 where the Mohawk is joined by the Schoharie Creek. A rise on the Schoharie will flush ice into the Mohawk.
In the Schenectady area, the railroad bridge over the Mohawk can cause ice problems; the numerous piers in the water, weather officials say, make "ideal" obstacles for traveling ice.
Montgomery said the weather service monitors the Mohawk with web cameras, but observers don't know how much ice is actually in the river. And they don't know if the ice will be affected by the coming warmup and rain.
"That's always the million-dollar question," Montgomery said. "Hence, the watch we have in effect. There's really a chance of some ice jams beginning to evolve with the increased warmth and with the amount of rainfall we're looking at."
Ice on the roads, Montgomery added, will be a worry for Saturday. There will be a giant drop from the balmy 50 degrees of Friday.
According to the weather service's forecast, "All areas may be susceptible to a flash freeze situation Saturday afternoon-evening, as any lingering unfrozen water on ground surfaces potentially quickly freezes with temps rapidly plunging into the teens-20s, if not lower in some areas."
Montgomery said this could mean hazardous travel. And while many may be off the roads Saturday, Montgomery said others may be driving to a destination during the long Martin Luther King Jr. Day holiday.
"It's going to be a multi-hazard event that will impact our region," he said.
Schenectady firefighters say they're ready. Assistant Fire Chief Michael Gillespie said firefighters and police are both in contact with the mayor's office when seasonal changes are in play.
He said there will be eyes on the Mohawk during the coming days.
"We will start monitoring as the weather gets warmer," Gillespie said. "We utilize the online information for water levels, river level changes, ice movement with the cameras and we routinely send — usually a platoon commander — down to various locations along the river to visually monitor what's going on."
Gillespie added the river is unpredictable.
"It had the ability to make a significant amount of ice over the past two and a half weeks," he said. "With this warmup, the rain coming and the breakup, it could cause what we would anticipate being minor flooding.
"We wouldn't anticipate at this juncture anything significant," Gillespie added. "It all depends just how that ice opens up."
He also said Stockade residents have been through flood alerts before. They have moved possessions from parts of their home that could flood, or are prepared to move them quickly if water seeps into their homes.
Reach Gazette reporter Jeff Wilkin at 518-395-3124 or at [email protected].