Only far northern Maine will be immune from the effects of warm, wet weather tracking farther east than meteorologists had anticipated.

Friday afternoon, the National Weather Service issued a flood watch for the entire state, except Aroostook and the northern tip of Somerset counties, warning residents that the combination of melting snow and several inches of rain could lead to widespread flooding.

“The situation is prime for a flooding event,” Lynette Miller, spokeswoman for the Maine Emergency Management Agency said Friday after a morning briefing with Gov. John Baldacci.

Much of the state experienced scattered rain and even hail Friday. Heavy rain, however, isn’t expected to begin until mid-day Saturday and continue through the weekend, dropping as much as 3 inches, according to the National Weather Service, which described the predicted storm as “a very efficient snow melter.”

“Those living and working near area rivers and streams should remain alert for rising waters this weekend,” the flood watch states.

The U.S. Coast Guard also issued a warning Friday, reminding boaters of the turbulence, strong currents and debris that spring floods can bring to rivers and coastal waters. Water temperatures this time of year can be as low as 38 degrees.

“A sudden spill into frigid waters will incapacitate most people within minutes,” Al Johnson, recreational boating safety specialist for New England, said in a statement.

Little more can be said before the storm begins, Miller said. By Saturday afternoon, the National Weather Service likely will have assessed the situation and issued flood warnings, if necessary.

“When it starts raining, we’ll see how much is falling and where it’s going,” she said.

The Penobscot River is all but clear of ice, so some risk of ice jam flooding has passed, emergency management officials said earlier this week.

For this weekend, state officials are particularly concerned about conditions on several Down East rivers and those in Piscataquis County, where ice remains.

Meanwhile, residents of northernmost Maine have been warned of “hazardous weather,” which could include heavy rain, though likely not enough to start ice moving on still-frozen Aroostook rivers.

“It’s still very much winter up in the St. John Valley,” Miller said.

For real-time weather information, including flood warnings and watches, visit the National Weather Service’s Caribou office online at www.erh.noaa.gov/er/car. For information on flood preparedness, visit the Maine Emergency Management Agency’s Web site at www.maine.gov/mema.