Good Morning everyone! Just a reminder this is Zach Robinson guest blogging for Kevin as he takes some time off. Today is my last blog post. Thanks for everyone chiming in and thank you to Kevin and The Roanoke Times for allowing me to blog.
Now… Let’s talk weather
Nothing changes really in our weather for the foreseeable future. Cool/Damp Mornings turning into dry/somewhat sunny afternoons as a weak easterly continues to dominate. The big story across the nation will be a major low pressure system that will become cutoff from the jet stream, and bring absurdly late snow to places from Denver to Minnesota. Linked are the HPC snowfall probability maps. (Midwest Snow) What is causing this snow? The snow today, over Minnesota is being caused by a series of shortwave troughs interacting with some forcing along a stalled front. As this happens an area of low pressure will begin to take shape just East of the Rockies and begin to close off somewhere over the South Central US. As this happens, at its peak negative tilt, it will bring snow to areas as far south as Kansas and Missouri. To the left is a screenshot of last night’s NAM model showing the upper level vortices on Friday afternoon.
What are we looking for here? Well we want the 500mb trough to go negative. You can see it is beginning to close off, and as it does so, it will take on a more of a NW-SE orientation. This is evidenced in the picture by the top end of the trough being situated more to the NW than the bottom end over Arkansas. (Linked here is a somewhat deeper explanation: Blue Ridge Weather) As this low continues to close off even more, it will eventually work in worm air from the South and the East and what cooling/forcing that we had will weaken to kill any snow chances. When a low goes negative like this one is doing, it really acts as an enhancer to colder air and precipitation rates. When you lose this forcing, you lose the snow.
Some of our most recent snows have happened when things become somewhat cutoff at the 500mb level. January 17th is a good example of this. February 19th of 2011 is a good example as well. However, I don’t think I have seen a storm match the May 7th 1992 storm that affected the NC Mountains. This storm cutoff completely from the Jet Stream at all levels, dumping up to 57” of snow on the mountains just outside of Asheville. Data is hard to come by, but a quick Google search will produce some pretty crazy stats and stories. Seeing as I was barely 1 when this happened, I was curious as to if SWVA experienced any snow from this? I have asked around and can’t seem to get a solid answer. Any stories on this would be awesome!!
Back to the forecast – - this low will slowly drift across the Central into the Eastern US – - likely affecting us in the form of rain showers by early next week. Until then, we are stuck in this stagnant, dull pattern. Enjoy it! It is time for me to head off to class, and this will conclude my last post this go round for Weather Journal. I hope you all found this enjoyable/informative and thank you so much for chiming in!!