As metropolitan Rochester experienced its first freezing temperatures of the season, forecasters cautioned that the first snowflakes Thursday evening could be accompanied by blustery winds and the possibility of dangerously icy roads.

Signs of impending winter are everywhere, it seems.

The National Weather Service issued three foul-weather advisories Wednesday, including one that warned a flash freeze could generate black ice on area roadways Thursday evening.

Rain showers are forecast Thursday afternoon in advance of a strong cold front. As the front passes through that evening, temperatures will fall sharply and rain will turn to snow showers, the weather service said.

The sudden drop in temperatures could cause precipitation to freeze on road surfaces, forming patches of what is known as black ice — a thin, all-but-invisible layer of ice that makes driving treacherous.

Winds will veer from southwest to northwest Thursday night, generating light snow squalls near Lake Ontario that will diminish visibility and making roadways even harder to navigate.

The winds are strong enough that the weather service had already issued a lakeshore flood watch for the entire New York shoreline of Lake Ontario, and a gale watch for the lake's open waters.

On Thursday evening, the weather service issued a lakeshore flood warning, citing strong winds, building waves and above-normal lake levels. At the shoreline, the wind-driven waves could cause significant erosion and minor flooding. The warning is in effect through 6 p.m. Friday.

Western New York will have to endure a genuinely wintry Friday: a high temperature of just 27 degrees, strong northwest winds and some snow showers.

The overnight low Friday into Saturday morning will be 18 degrees in metro Rochester and colder in the hills to the south. Wind chills will approach zero degrees.

Rochesterians got a taste of that wintry chill Wednesday morning when they awoke to a thin layer of ice on puddles and ponds, compliments of temperatures that fell below the freezing mark shortly before 12 midnight and stayed there until about 8 a.m.

It was the first freeze of the season in urbanized Monroe County. Communities south of Rochester that sit at higher elevations have already experience temperatures below 32 degrees several times this month.

The air will warm slightly on Saturday, and return to near-normal temperatures on Sunday and Monday.

It may seem early for snow, especially given how unusually warm autumn has been so far, but the flakes are actually a bit behind schedule.

On average, the first short-lived flakes are spotted in Rochester on Oct. 23, according to weather service climate records.

Our first measurable snowfall occurs, on average, on Nov. 8. Measurable snow is defined as one-tenth of an inch or more.

The snow flurries expected Thursday night (Nov. 9) will be the first flakes in Rochester, and the first accumulation, of the 2017-18 winter season.

SORR@Gannett.com