Snow began falling on Long Island before daybreak Tuesday, with a forecast of 1 to 2 inches for most of Nassau and Suffolk counties, the National Weather Service said. Although the outlook is mild by recent standards, the timing of the storm -- during the morning commute -- could make for challenging driving conditions.

A winter weather advisory is in effect until 6 p.m. Tuesday, the service's Upton office said.

"Pockets of light to moderate snow will track northeast across the area over the next couple of hours," the service said in a special weather statement about 6 a.m. "Some of the heaviest activity will be capable of producing one-half to one-inch an hour rates."

Tim Morrin, a meteorologist with the Upton office, said the forecast of 1 to 2 inches covers most of Long Island west of Riverhead. Parts east, he said, should get more rain than snow, with Tuesday morning temperatures slightly warmer on the North and South forks.

The service said driving during the morning commute could be difficult. With temperatures between 20 and 30 degrees "snow will begin to accumulate on area roadways, making for slippery travel."

The snow likely will change to mostly rain sometime after noon, the service said, with temperatures warming into Wednesday, and more rain is possible.

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The chance of precipitation for Wednesday is 40 percent with a daily high in the mid-40s.

Skies clear by Wednesday night. By Thursday, the forecast is for mostly sunny skies with highs in the upper 40s, the service said.