Good news for most of South Florida: Isaac is not going to get worse, at least for Miami-Dade, Broward and Palm Beach counties.

By early afternoon Sunday, forecasters said the tropical storm had probably delivered its biggest and windiest punch — with gusts along the coast peaking at 55-miles-per-hour overnight but considerably less inland.

More gusty bands could still roll across mainland South Florida but they were unlikely to get stronger, said Robert Molleda, warning coordination meteorologist for the National Weather Service’s Miami office.

“The strongest winds we’ll get are going to come now and this afternoon,’’ said Molleda during a 12:30 p.m. phone briefing.

The Florida Keys, however, will remain under the gun for most of the day as Isaac approaches. But the latest advisory, issued at 2 p.m., said the threat that Isaac would strike Key West at hurricane strength is decreasing.

Molleda said that a slight shift westward in Isaac’s track had kept the strongest winds around the storm’s still disorganized core away from the mainland. He cautioned that fast-moving squall lines could still generate for much of the evening.

But he predicted that tropical storm force gusts would largely clear the Southeast coast by midnight.

In a sign of Isaac’s diminishing threat to Miami-Dade, the National Hurricane Center lifted a hurricane watch for the county’s coastal communities.

A tornado watch and tropical storm warning remained in effect, however, as winds are expected to steadily worsen — spreading from the Keys north across Miami-Dade and Broward counties throughout the day and into early Monday morning.

Wind gusts of 55- to 60-miles-per hour began at about 6:30 a.m., felling trees and blowing debris that have knocked out power to thousands of homes in Miami-Dade and Broward counties.

About 3,400 homes in Miami-Dade and another 1,400 in Broward were without power at 11 a.m. Sunday, according to Florida Power & Light.

In addition to strong winds, Isaac is expected to dump four to eight inches of rain on South Florida, potentially flooding already saturated neighborhoods. Rough seas and storm surge also could spill over roads and docks.

In Broward’s coastal cities of Hallandale Beach and Hollywood, where low-lying neighborhoods are prone to flooding, officials continued to hand out sandbags on Sunday morning after filling thousands the day before.

At 11 a.m., Isaac’s winds remained at 65 mph, but the storm is slowly organizing and a partial eye wall has formed. It was located about 66 miles southeast of Key West.

THREAT TO KEYS

Though Isaac’s winds had slowed some as of 2 p.m. Sunday, meteorologists expect the storm will strengthen over the next 48 hours.

Isaac is predicted to continue moving generally in a west-northwest direction through Monday after passing the Florida Keys.

Though it is too early to determine exactly where Isaac will make landfall along the Gulf Coast, a hurricane watch was posted from Morgan City, La., west of New Orleans all the way east across to near Apalachicola on the northeastern Florida Panhandle. Forecasters are predicting it will make landfall on Wednesday morning.

In Miami-Dade, the threat of Isaac appeared to fizzle almost as soon as it rose.

The county’s Emergency Operations Center launched to Level 1 Sunday morning — its highest alert, with the center fully activated, and all agencies represented.