A special weather statement from Environment Canada is calling for 5 to 10 centimetres of snow to fall Thursday night into Friday morning.
Environment Canada Meteorologist Geoff Coulson calls it a "shot across the bow" as winter approaches.
The morning forecast had only called for 2 to 4 centimetres, but Coulson says a steady band of snow moving along the Great Lakes required an update.
"We're seeing a fairly steady band of snow from the Muskoka area eastward toward Bancroft and into the Ottawa area, and that's resulted in bumping up the snow amounts for Ottawa."
It's going to make for a bit of a messy drive Friday morning.
"The temperatures will be around the freezing mark, and there will be some melting going on. We're also going to see the snow mix with rain overnight as those temperatures fluctuate around the freezing mark. That mixture of snow and rain will continue into the morning hours on Friday."
It's not going to be a permanent blanket of snow. Temperatures are expected to rise on the weekend, melting it all away.
"Looking at the forecast into the first part of November, our forecasts in through Tuesday and Wednesday of next week see temperatures bouncing back to double digits for the highs. 11, 12 degrees Celsius. So, it's going to be a little bit longer into November before we probably see the first notable snow that's going to stick around."
Coulson says although there's no harm in getting to it earlier, Ottawa residents still have some time to get their snow tires on.
"I think this is still probably a good shot across the bow to remind everybody that snow is a possibility during the course of the coming weeks. Certainly I wouldn't want to discourage anybody from getting out there over the course of the next little while to get those snow tires on. This particular event is going to be relatively short lived, but certainly as we get further into the month of November we are going to start seeing more in the way of snowfall."
Thursday's snowfall is to be followed by some overnight rain and a jump in temperature on Saturday with a high of 15 degrees.