Heavy Rain Could Make Waves At Lake Hopatcong

HOPATCONG, NJ — Heavy rain forecast for Hopatcong could raise Lake Hopatcong on Thursday, even though Morris and Sussex counties are outside northeastern New Jersey's flood watch.

The National Weather Service expects showers and thunderstorms in Hopatcong Borough on Thursday. The region could receive a half-inch to 1 inch of rain, with localized totals of 2 to 3 inches possible as forecasters warn that "the localized threat has increased."

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For residents, a heavy downpour could mean water collecting on low-lying roads, a slower commute and possible flooding in basements or yards with poor drainage. Drivers should leave extra time, avoid standing water and never attempt to cross a flooded roadway.

At Lake Hopatcong, rainfall has an amplified effect. New Jersey's water-level management plan estimates each inch of precipitation can raise the lake about 2 inches, although the response depends on storm intensity, duration and saturated ground.

The lake is managed near its 9-foot spillway level during summer. If it reaches 9.5 feet, New Jersey State Police issue a no-wake restriction to reduce shoreline erosion and damage to docks and other structures. That could also require boaters to slow down and change their plans.

For Hopatcong residents, lowering the lake is not as simple as opening the dam gates. While releasing water can help protect local docks, shoreline properties and waterfront homes, that water flows into the Musconetcong River, where other properties sit in the floodplain. State park officials must balance the risk to Hopatcong neighborhoods against the possibility of worsening flooding downstream before adjusting the gates.

That balancing act means a fast downpour can raise the lake more quickly than officials can safely release water. Waterfront residents may want to secure loose items near docks, while everyone should monitor forecasts and allow extra travel time Thursday.

Have a correction or news tip? Email dani.sepe@patch.com.