Late Thursday Evening Update

well, quite the busy Thursday - espescially for areas south & east of Louisville...

NO more severe weather threats for at least the next 2 to 4 weeks and maybe longer as the atmosphere is getting ready to under some pretty major changes. Colder weather is headed back in (slowly at first), but some arctic air should be arriving by later next week.

Alright, let's get into this. First of all absolutely NO chance for a BIG snow herein the Ohio Valley this weekend. A couple of shortwaves will be running through the mean trough that will be developing over the Mississippi and Ohio Valleys this weekend but with upstream kickers and no blocking pattern, the velocities will be way too strong for any phasing of northern and southern streams and these shortwaves will continue to be very progressive at least while passing over our area.

The first system we are talking about will push through on Sunday. One vort max passing well south and another passing through our region. Any surface reflection with this upper feature will be weak and quite disorganized so only light precip is expected. Temps from H85 and higher will be cold enough for snow... but the low layers will be way too warm at least for SunDAY. Later Sunday night, after the weak sfc system passes east, CAA (cold air advection) will overspread the region and cool the lowest layers of the atmosphere so any left over light rain will change to a period of light snow or flurries. NO accumulation expected with this first wave.

Another short (clipper type vort lobe) will push towards the region for Monday night. This system will bring us another chance at some light snow - but any accumulations will likely be quite low due to its quick movement and the fact that the low level features with this H5 shortwave will again be very weak and disorganized.

I think things could get quite interesting beyond the 7day forecast period. For the first time in the last 3 to 5 weeks, a major piece of jet energy crashing into the far NW and West Canada i9s expected to close off and become teh polar vortex. This will send a batch of arctic air south into the US. Temperatures across our area will likely hold in the 20s to near freezing after the arctic boundary passes through.

One thing we will have to watch for, is this pattern becoming established for a long time period. I believe the key for possible major snow, ice, winter storm activity will be the eventual upper air setup in the Pacific ocean. It appears a major ridge will be developing over the eastern Pacific up into Alaska. Some of the models are suggesting that this upper high / ridge will become cutoff and essentially become a block with pacific jet energy undercutting this ridge and passing into the United States. This is VERY important for winter storm activity for our area. The reasons: 1) with the block in place, this northwest flow from the arctic into the United States will continue to bring down shots of cold air, 2) the pacific energy undercutting the ridge will ensure systems pass into the western US and move east across the southern plains into the OH and TN valleys.

With the cold air in place...presto !! snowlovers keep your fingers crossed.