Oh yes, it’s happening: A Frost Advisory has been issued to start the weekend in Metro Detroit. The National Weather Service has issued the advisory, which takes effect at midnight until 9 a.m. on Saturday. Clear Saturday night, with lows in the low to mid 40s (5 to 7 degrees Celsius). Mostly sunny on Sunday, and a tad warmer with highs in the mid 60s (18 degrees Celsius). Clear Sunday night, with lows in the mid 40s (7 degrees Celsius).