As we shivver through yet another day of the Arctic Outbreak across the Tri-State, we are another day closer to our first accumulating snowfall of the season this weekend. While the models have been flip-flopping somewhat, I am a little more confident that some snow is a good bet on Saturday and again on Sunday.
The first ingredient we need for snow is cold air, and we certainly have and will have a deep enough layer of sub-freezing air to support snow over the weekend. The tricky part of this forecast will be the amount of moisture that is available and the behavior of a cold front and weather system that will provide the lift to get snow going. The above chart shows we'll have between .05 and .10" of water equivalent in the atmosphere Sunday through Monday.
Using a simple 10-to-1 ratio, this would yield between a half inch and one inch of snow if all of the moisture is realized as snow. While this isn't a lot, it will be enough to coat roads and create hazardous travel, especially over Kentucky on Sunday night and early Monday morning.
The surface forecast chart for Sunday shows a low spinning across the UP of Michigan. The trailing cold front will help lift moisture and get the snow started. We may see a brief period of snow on Saturday night, but the amounts will be very light:
Here is how I think the event will play out, based on today's data: Saturday afternoon will bring temps in the 30's. Late afternoon light rain will change over to snow in the evening with less than an inch in the northern half of the Tri-State:
As the first system drops south of the Ohio River on Sunday, a secondary piece of energy will cause moisture to glide up and over the cold air at the surface, especially to the south of the Ohio River. This will result in more accumulation by Monday morning over Kentucky:
So, you're probably wondering if this early taste of winter is a sign of things to come for the season. I have been researching past winters to find a similar temperature/precip scenario, and I didn't have to look very far. Check out the charts for average monthly temperature for this year and last year:
Do you see any similarities ? If you just look at the purple temperature line, you can see that almost the same pattern is repeating again so far in 2014. We remain in an El Nino neutral pattern, which means we will likely have a winter similar to the last two UNLESS El Nino can develop, and that doesn't appear likely in the next month. I'll explain more of the details and how this will impact our temperture and snowfall forecast for Winter 2015 in my Winter Forecast, tonight on 14News at 10.