A winter storm will pass through our region Sunday but questions still remain on placement of snowfall and amounts.
Sunday/Sunday Night Rain to Snow. Potential heavy amounts.
Next Thursday Snow/Mix changing to Rain.
We still have a good 24 hours ahead of us in terms of gathering some key data on this Sunday system. Having said that, we can at least get a good story-line of how this is looking...
Setup... energy moves into California tonight/Saturday. Once it emerges near northern Texas, low pressure develops. The flow will be fast that will guide our new friend. It will zip along quickly into Tennessee. It will get stronger as it moves east but it will likely be east of I-65 before it becomes an impressive low. It will then continue to deepen as it moves up the NE coast to bring inland areas a very heavy snow...pulling in Atlantic moisture.
Timing... the atmosphere will start to automatically increase moisture Saturday night near/west of I-65 as that low develops in Texas. Looking at temperature profiles, this looks to be mainly rain. Once the low moves into Tennessee Sunday midday, the “warm” core looks to push into central & eastern Kentucky. Mainly rain in those locations. The northern and northwest side will begin to mix with or change to a heavy wet snow. “Heavy” being the key word there as if rates are too light, there is a risk the rain could last longer. Temperatures at the ground level will likely stay above freezing during the daytime period. You can still get an accumulating snow, just have to have the rates with the temperature drop. The speed & timing of the low deepening are going to be key on this. Sunday night we do get colder air to move in but the low will be to our east at that point. That means a narrow window of heavy snow otherwise easing back down to light rates. And not to pile on here, but if we are not cold ENOUGH by this period in time...the snow could actually change back to drizzle then end.
Snowfall... Considering the above, there is certainly a bust and overachieving potential with this setup. Modeling is good, but isn’t the best on mesoscale features that make a difference on temperatures and rates. Those issues will go down to the wire to get resolved. But we need to make a forecast, right? That is where our stress kicks in :) I can see the argument for both sides of here heavier snow bands as well as a longer rain duration. Both have happened here before. One thing I am looking at is the amount of wet-bulbing (cooling of the atmosphere) we could gain early Sunday. If that portion of this equation is limited, I may lean more toward the longer rain/limited snow idea. Until then, I have go do with the data I do have now and that still suggests 4″ totals possible a few counties either side of I-64. Could we see more than that? Yes, total potential liquid is roughly .50 to .70″ so if we are colder than expected, we can take advantage of that moisture. Just be aware that the opposite applies as well...if we take longer to get cold, the snowfall will be less than impressive. I am sure you snow-lovers just screamed at me, but these are the challenges we face at this latitude. Small changes have big outcomes.
Impacts... While the potential heavy snow will lead to issues on its own, the main concern will be the drop in temperatures into the teens Monday morning. If there is enough snowfall, icy roads will be a big threat. If we end up with a bust setup, the wind COULD help dry up the roads to limit icy patches to sheltered locations. Either way, Sunday night/Monday morning does feature some travel hazards.
Very cold weather is still in the works for Mon/Tue (how low will depend on snow pack) with us pulling out of this cold wave by Thursday.
Hopefully this all made sense!
The video has more info of course...