Storm time

On Saturday I outlined the expected pattern change that would be taking place during the February 10-24 period. In that discussion I noted that a split flow was developing and that…

split flow patterns provide the access to the moisture (sub-tropical jet) and cold air (polar jet) necessary for major winter storm formation. Timing will be the key, as shortwaves from each jet will need to phase together to develop a big storm.

and also…

If the split flow does persist, I think the probability of at least one major winter storm in the eastern U.S. is fairly high…in the Feb 10-24 period. Regardless, this pattern should be much stormier than what we’ve seen the past two weeks under the dominance of the polar vortex.

Well, sure enough, there is growing evidence of at least one and possibly two major winter storms that will affect the eastern half of the U.S. next week.

The first storm will likely move across the southern plains and across the TN valley Monday and Tuesday of next week (before Valentine’s Day). You can see from the ensembles that there is very good agreement that 1) the storm will occur and 2) there will be a lot of moisture associated with it. The fact that the polar vortex will remain over SE Canada will assure enough cold air so that the northern part of this storm will see a heavy snowstorm (6″+). Where will the heavy snow fall? Well, one estimate of where the snow may occur can be found here, but the location of the rain-snow line as well as snow amounts won’t be known for several days. My gut feeling is that south-central KY is more likely to see rain or ice from this as opposed to a big snow. The amount of WAA that got into our area with the storm from Tuesday’s non-storm has me worried.

Storm #2 is a little more speculative and only shows up on a few of the ensemble runs. However, the overall pattern does support a series of storms as the sub-tropical jet re-energizes.

The Bottom Line:
A strong winter storm will move across the southern states early next week producing ice and snow to the north and heavy thunderstorms (and possibly severe weather) to the south. The actual location of the rain-snow boundary is to be determined but the early evidence suggests it will be north of south-central KY. However, there is the potential that parts of the mid-south could receive significant amounts of wintry weather from this system.

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