There has been a dramatic shift in weather developments here over the past 24 hours! Since Monday, we've made mention of a light wintry mix of rain and snow for Thursday, but my how things have changed! All of our computer models have shifted the track of that system to the South, which elevates our risk for potentially significant snowfall!!
The afternoon run of our in-house Timecast model (technically referred to as the RPM (Rapid Precision Mesoscale) model) exhibits quite the spread in accumulations throughout the Stateline! While the afternoon runs center the bulk the snowfall right over the US-20 Corridor, it's important to note that this narrow band of the heaviest snowfall has been shifting north and south throughout the day, and further jogs can't be ruled out in coming runs! For that reason, we emplore you to not use these numbers as gospel, as subtle shifts in the track will slide that heaviest axis in one direction or another! Such a shift has been noted in the evening run of that model, now favoring Southern portions of our viewing area, though it's not nearly enough of a shift to deem it as being conclusive evidence!
Given the amount of uncertainty amongst our computer models, I've gone ahead and blanketed the entire viewing area in the range of 3" to 7" of snowfall. That said, I wouldn't be at all surprised if many of us failed to reach 3" while a few localized areas picked up even a bit more than 7". My hunch, given all the wild cards that are in place, I feel as though most of us end up on the lower end of that 3-7" spectrum, generally in the 3" to 5" range.
Beyond the track of the storm and where the bands of heaviest accumulation are to set up, believe it or not, there are EVEN MORE forecasting wild cards!
The first wild card deals with the fact that the ground is quite warm! Much like we saw early Tuesday morning, when about an inch of snow came down here, that snow stuck around for just a few hours, with much of it having melted on contact due to the warm ground, and the above freezing environment into which the snow was falling. With two more 40+ degree days since that snow, the ground's still plenty warm, and could trim accumulations some.
Secondly, there's a possibility that there could be a period in which the snow is to mix with rain. This, too, would have a negative impact on accumulations, though this appears to be the least likely wild card to have a major impact here.
Wild Card #3: THUNDER! There's a ton of energy in this system, and air will be ascending wildly upward at times, fostering heavy, wet snow bursts along with embedded claps of thunder. Anytime you're dealing with thundersnow, it's entirely possible that snow could fall at a clip of 1-2" PER HOUR! So if we're to have any bursts of thundersnow, albeit on the local scale, accumulations could be quickly enhanced, perhaps to the point of even being able to overcome the warm ground!!!
All things considered, this storm system, given the massive amount of wild cards and uncertainties, is a forecaster's nightmare! (Especially since just Tuesday, this looked like little more than just a light rain/snow mix!) All that said, we'll be combing through every piece of data we can get our hands on through the evening and provide updates as needed!