Southwestern St. Lawrence County is under a lake effect snow warning through Friday morning, according to the National Weather Service.

Meteorologists say drivers should plan on difficult travel conditions due to heavy snow. Total accumulation is expected at 1 to 3 inches with "localized amounts" up to 12 inches.

NWS says the effected area will be mainly south of state Route 68 and east of U.S. Route 11.

Drivers should also prepare for "significant reductions in visibility," NWS said.

NWS is listing the lake effect warning for Canton, Potsdam, Gouverneur, Star Lake and Ogdensburg areas. The Massena area is not listed with the warning.

Wednesday night, the NWS says the Canton area could see less than half an inch of snow; Gouverneur area 1 to 2 inches; and less than half an inch around Potsdam. Temperatures are predicted in the high 20s.

Thursday brings slight chances of snow and snow showers around St. Lawrence County with temperatures in the mid 30s.

Thursday night is forecast to be mostly cloudy around Massena and Potsdam, and brings 30 to 40 percent chances of more snow elsewhere. Temperatures are forecast in the mid 20s.

Friday should be partly sunny in Massena with 30 to 40 percent chances of snow in the rest of the county, with temperatures in the low 30s, NWS said.

The detailed forecast for Potsdam:

Wednesday night - A chance of rain and snow showers before 7pm, then a chance of snow showers. Mostly cloudy, with a low around 27. Southwest wind around 10 mph, with gusts as high as 20 mph. Chance of precipitation is 40%. New snow accumulation of less than a half inch possible.

Thursday - A slight chance of snow showers before 3pm, then a slight chance of rain and snow showers between 3pm and 4pm, then a slight chance of snow showers after 4pm. Mostly cloudy, with a high near 35. Southwest wind 9 to 11 mph. Chance of precipitation is 20%.

Thursday night - Mostly cloudy, with a low around 25. Southwest wind around 10 mph.

Friday - A 30 percent chance of snow showers. Mostly cloudy, with a high near 32. Southwest wind 7 to 10 mph. New snow accumulation of less than one inch possible.

Friday night - Mostly cloudy, with a low around 22. Southwest wind 6 to 8 mph.

Saturday - Mostly cloudy, with a high near 33. South wind around 6 mph becoming west in the afternoon.

Saturday night - A 40 percent chance of snow showers. Mostly cloudy, with a low around 17. Light northwest wind.

Sunday - A 40 percent chance of snow showers. Partly sunny, with a high near 27. West wind 5 to 7 mph.

Sunday night - A 30 percent chance of snow showers. Mostly cloudy, with a low around 16. Southwest wind 6 to 8 mph.

Monday - A 50 percent chance of snow showers. Mostly cloudy, with a high near 32. Southwest wind around 10 mph.

Monday night - A 50 percent chance of snow showers. Cloudy, with a low around 19. Southwest wind 5 to 9 mph.

Tuesday - A 40 percent chance of snow showers. Mostly cloudy, with a high near 27. West wind around 6 mph.

Tuesday night - A 50 percent chance of snow showers. Mostly cloudy, with a low around 10. North wind around 6 mph.

Wednesday - A 40 percent chance of snow showers. Mostly cloudy, with a high near 19. Northwest wind 7 to 10 mph.