A “Pineapple Express” weather system hit Boulder later than expected Thursday, after a thick layer of fresh, heavy powder blanketed Colorado’s high country.

“If you’re skiing, I hope you brought the snorkel,” quipped meteorologist Joel Gratz in a post Thursday on opensnow.com.

Eldora Mountain Resort received 18 inches of snow in the 24 hours leading up to 2 p.m. Thursday, according to snocountry.com.

In Boulder, as the sun went down Thursday evening, rain turned to wet snow, which was accumulating into what could make for a messy morning commute Friday.

Forecasts originally called for the storm to move into Boulder early Thursday afternoon.

The National Weather Service, in a winter storm warning in effect until 6 a.m. Friday, was calling for persistent, sometimes heavy, snow along the Front Range overnight. The warning predicted 5 to 10 inches of accumulation in most places, with a foot of snow possible in some areas.

The storm system is partly the result of a weather phenomenon in the tropics. The “Pineapple Express” — moist air that forms in the Pacific near Hawaii — was pushed across the southern U.S. and into Colorado, bringing potential for significant snowfall.

“Basically a ‘Pineapple Express’ is talking about a tropical area with all this moisture, and that moisture is being funneled up into the area,” said Dan Leszcynski of the National Weather Service. “It’s bringing in the moisture from the Gulf, then across the Southwest U.S. and then right into Colorado.”

Snow removal crews were on alert and “prepped and ready for the storm,” said Boulder public works spokesman Mike Banuelos.

Friday’s forecast calls for a 50 percent chance of more snow, according to the weather service. The chance of snow carries over into the evening.

Saturday brings a 30 percent chance of snow in the morning.

Sunday is expected to be sunny with a high near 28.

Contact Camera Staff Writer Joe Rubino at 303-473-1328 or rubinoj@dailycamera.com.