Snow is streaming off of Lake Ontario in strong southwest winds, bringing snowfall into St. Lawrence County, especially southern portions, as the National Weather Service has posted lake-effect snow warnings and hazardous weather advisories.

Snowfall overnight caused schools in Gouverneur, Edwards-Knox, Clifton-Fine and Harrisville to close their doors today.

The chance of snow today in Star Lake is 100 percent, according to the NWS; it’s 50 percent in Potsdam and 30 percent in Massena. Winds will be gusting up to 40 mph.

Four to eight inches of snow are expected accumulate today in the southern portion of the county, and lesser amounts as you go north.

The high in Star Lake is not expected to reach 20 degrees today. Farther north in the county, temps will rise to the upper 20s.

Today and tonight, as much as 15 inches of snow could accumulate in Star Lake. Three inches at most is expected in Potsdam. Just a dusting can be expected in Massena.

Snow showers are predicted, on and off, through Thursday. Temperatures will reach the 20s to low 30s in the daytime, and drop as low as 14 degrees Thursday night in Star Lake.

The National Weather Service forecast for the St. Lawrence Valley and northwestern Adirondacks:

• Today: A 50 percent chance of snow showers. Increasing clouds, with a high near 26. Breezy, with a southwest wind 16 to 22 mph, with gusts as high as 40 mph. Total daytime snow accumulation of less than a half inch possible.

• Tonight: A 50 percent chance of snow showers, mainly before 4am. Cloudy, with a low around 21. Breezy, with a southwest wind 13 to 20 mph, with gusts as high as 36 mph. New snow accumulation of 1 to 2 inches possible.

• Wednesday: A 40 percent chance of snow showers, mainly after 9am. Cloudy, then gradually becoming mostly sunny, with a high near 27. Southwest wind 11 to 14 mph, with gusts as high as 24 mph. New snow accumulation of less than a half inch possible.

• Wednesday Night: Snow showers likely, mainly after 2am. Cloudy, with a low around 21. South wind 7 to 11 mph, with gusts as high as 21 mph. Chance of precipitation is 70%. New snow accumulation of less than a half inch possible.

• Thursday: Snow showers. High near 33. Southwest wind 9 to 18 mph, with gusts as high as 32 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 3 inches possible.

• Thursday Night: A 40 percent chance of snow showers. Mostly cloudy, with a low around 18. West wind 9 to 13 mph.

• Friday: A 30 percent chance of snow showers. Mostly cloudy, with a high near 25. West wind around 10 mph.

• Friday Night: Partly cloudy, with a low around 10. West wind 7 to 9 mph.

• Saturday: Partly sunny, with a high near 31. Southwest wind 7 to 10 mph.

• Saturday Night: A 30 percent chance of snow showers. Mostly cloudy, with a low around 27. South wind around 11 mph.

• Sunday: A chance of rain and snow showers. Mostly cloudy, with a high near 43. South wind 7 to 11 mph. Chance of precipitation is 50%.

• Sunday Night: A 50 percent chance of showers. Cloudy, with a low around 38. South wind 6 to 9 mph.

• Monday: A 50 percent chance of showers. Cloudy, with a high near 53. South wind around 9 mph.