Winter is officially here, as of 6:12 a.m., and Western New York won’t have long to wait for its first major winter storm. It’s coming tonight.

The National Weather Service has upgraded an earlier winter weather advisory into a winter storm warning from 11 a.m. today through 4 p.m. Saturday for the traditional Snow Belt areas in the Southtowns and the Southern Tier.

Rain is expected to mix with snow during the day, then turn entirely to snow later this afternoon in the warning areas. An inch or two may accumulate by sundown, forecasters say, with the bulk of the snow, 4 to 7 inches, coming later tonight. The snow is supposed to continue Saturday morning, producing a storm total of 8 to 14 inches, with the deepest snowfall running from the Boston Hills southward along the Chautauqua Ridge.

It will be good news for the ski resorts, which have had a tough time making snow during the mild weather so far this month. The website for Peek ’N Peak in Clymer reports that its slopes will officially open Sunday but may get an early start on Saturday.

With temperatures around 30 degrees, this is likely to be heavy, wet, slippery snow, making highways slushy tonight. But that’s not all that motorists will have to face when they venture out after dark.

Winds, due to diminish earlier in the day, are forecast to increase again tonight, gusting to 35 mph and producing drifts and whiteouts, especially in Southern Erie and Chautauqua counties. Travel between Hamburg and Ripley, even on the Thruway, is likely to be treacherous.

Meanwhile, a winter weather advisory has been issued for the rest of the region from 4 p.m. today to 4 p.m. Saturday. Snow is expected to accumulate 2 to 3 inches tonight and another 2 to 3 inches Saturday. Near the lake shores, accumulations should start later and be lighter, perhaps as little as an inch or two.

Occasional periods of snow are expected through Sunday, with a dry and sunny forecast for Christmas Eve on Monday.

Temperatures are supposed to stay seasonably cool, with daytime highs around the freezing mark and overnight lows in the low to mid-20s, which will keep the snow from melting and guarantee a wall-to-wall white Christmas almost everywhere.

For a final touch, the forecast for Christmas Day calls for occasional snow showers.

The storm is likely to double or triple the official amount of snow that’s fallen so far this season at the National Weather Service office in Cheektowaga, but things will still be far below normal. On the average, Buffalo has gotten 25 inches of snow by this date.

Until the snowflakes start falling today, this year’s total is only 2.7 inches.