May 28

Today was another relatively easy day with a scenic drive from North Platte to Norfolk, NE. We were treated to a spectacular view of the Sand Hills while traveling along Highway 83. The main attraction for today was the Ashfall Fossil Beds State Historical Park (http://ashfall.unl.edu) near the town of Royal. These ashfall fossil beds were created by an enormous volcanic eruption in Idaho about 12 million years ago that shrouded much of the Plains in ash, including this area in northern Nebraska. The animals (horses, camels, birds, and rhinos) that lived during that time inhaled the ash and slowly suffocated. After their demise, they were covered in several feet of ash until they were discovered in 1991. One of the rhinos discovered was named 'Justin' and was probably only a month old when it died.




The weather today was once again chilly with highs struggling to reach the mid 50s under cloudy skies and occasional drizzle. Tomorrow is setting up to be much warmer and a potential chance for significant severe weather. A strong shortwave moves through Nebraska tomorrow as a triple point sets up in southwest Nebraska. Ahead of the dry line, low pressure center, and cold front, there should be plenty of warm and moist air to fuel the storms that form tomorrow. Wind fields, wind shear, and instability all look quite favorable for the development of supercells and tornadoes.

A couple of concerns I have at this point are moisture return and whether the morning convection can clear out, which will have a large impact on instability. At the time of this posting, it appears as though the new 00Z NAM has backed off on dew points and instability somewhat for tomorrow, especially for northeast Nebraska. This seems reasonable to me given that a large area of convection is growing in coverage and intensity across west-central Nebraska late this evening, and this should limit the amount of moisture return overnight. I expect dew points to top out in the mid 60s in this area, but regardless, MLCAPE values should be between 1000-2000 J kg-1. The timing of the storms will also play a large role in the convective evolution tomorrow. If the convection clears out of eastern Nebraska early in the morning, there should be plenty of time to recharge the atmosphere for another round of late afternoon storms. However, if the storms take a longer period of time to exit the state, this may tend to limit instability further and may shift the better threat of severe weather further south and west.

While I would hate to leave the front in north-central Nebraska, the convective setup is becoming more interesting for southern Nebraska and northern Kansas. It appears that this area will be closer to the better moisture and be less impacted by the complex of storms across northern Nebraska. While there is no discernible boundary in place (although a valid argument could be made for residual outflow boundaries possibly lingering around), a secondary surface low is forecast to develop across northern Kansas tomorrow evening. If this scenario occurs, the winds could locally back ahead of the low and provide a more favorable low-level shear environment for supercells. Additionally, the strength of the wind fields increases in the evening, and this could prolong the threat of tornadoes after dark if storms can remain discrete.

Tomorrow is quite a difficult storm chasing forecast, but I'm still leaning towards the front in north-central Nebraska (Burwell) until after watching the thunderstorm complex evolution in the morning. My backup target would be Holdrege in south-central Nebraska.