Major Winter Storm Valentine's Day

The latest model data shows a major winter storm from a strong Alberta Clipper moving into the region late Sunday evening lasting into Monday evening. A winter storm watch is now in effect for most of Southern Indiana and Kentucky from 4pm Sunday through 7pm Monday. The snow events will come in three waves, with the first beginning Saturday night into Sunday morning. Accumulations of 1-2" are possible. The main event will come Sunday afternoon into Monday morning with most of the snow coming from this time frame. Some wrap around moisture may come on Monday evening bringing another quick inch of accumulation.

At left is the latest probability from the HPC of at least 4" of snow. Prob of 8" is center and prob of 12" is far right.
Red = 70%
Green = 40%
Blue = 10%

With that said, here is my forecast graphic for what to expect. Going to go with generally 3-5" across our area, though locally higher amounts could easily be possible depending on how high the snow to liquid ratios become. With the first wave from the surface low tonight, a 10:1 ratio is probable. However ratios could be as high as 16:1 or even 20:1 as the cold, arctic air begins to set in behind the front. As of right now, the NAM is churning out 0.22" liquid and the GFS is at 0.36". The NAM seems to be underestimating the liquid as it has in some previous winter storms this year. I like the GFS much better. At at 20:1 ratio, that could mean as much as 7.2" and 5.76" at a 16:1 ratio! Because some of this will occur at the 10:1 to start, going with 3-5" generally across the area, but won't be surprised at locally higher amounts.