Parts of Huddersfield could wake up to several inches of snow in the morning.
And the warning from Huddersfield weatherman Paul Stevens is: It may stick around for days.
The Met Office and the Highways Agency announced this afternoon that an "amber alert" had been confirmed for the north, which includes the Yorkshire region.
The M62 and other trans-Pennine routes are said to be at serious risk of disruption.
The alert will come into force at 5pm today - Wednesday - and run until 11am tomorrow.
Commuters have been urged to drive with extra care.
Temperatures dropped noticeably this morning and the winds blew in gusts of up to 65mph before a spell of brighter weather hit the town.
But forecasters have agreed that a band of snow showers borne in on strong westerly winds is set to hit the Pennines later tonight.
That could mean streets in the town centre seeing anything from 2 to 5cm of snow but places such as Holme Moss having up to 30cm, or 12 inches of snow.
The moors could well see very strong winds blowing the snow about in blizzard-like conditions.
Mr Stevens, of Salendine Nook, said: “We had temperatures up to 8°C this morning but by 11am that had dropped to just 2° and several areas had seen hail or snow showers.
“The key is that we are talking about showers and it is impossible to predict how and where they will fall.
“Back in December 2009 Huddersfield had exactly the same conditions and the bands of snow showers we got then started on Sunday afternoon and carried right through until Monday, leaving some areas with 25cm of snow.
“I certainly think everyone will see some snow but just how much and when is difficult to predict. I think in the town centre there could be a couple of centimetres but many higher areas could see anything from 5 to 10 cm and up on the hills and moors, there could be three times that.
“There is even a 20% chance that some of the higher ground could see it get to 30cm and with strong winds it will blow around.
“Friday should be a little milder but it is only a lull as we will see a real blast of Arctic air hitting the town at the weekend, with temperatures struggling to get above freezing. It is set to stay like that for up to seven days and we could well see more snow”.