Severe Weather Looks to Return Tomorrow

May 19th, 2021
The Storm Prediction Center has issued a Slight (Level 2) Risk for severe weather in Eastern...
The Storm Prediction Center has issued a Slight (Level 2) Risk for severe weather in Eastern Wyoming and Western Nebraska for Thursday May 20th, 2021(KGWN)
Updated: May. 19, 2021 at 12:25 PM CDT
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Temperatures are climbing around much of Wyoming as the back half of the week looms, continuing a trend the state has seen in recent weeks: warm Thursdays. The past few Thursdays have been either the warmest or nicest days of the week, with a few of them being both. This Thursday will continue one of those trends, however not both. Temperatures are expected to reach their peaks tomorrow afternoon with the eastern and central regions of the state climbing to highs in the upper 70s and lower 80s. While it will feel pretty nice outside for much of the day, the setup overhead in regards to weather isn’t exactly what you would want to see with the warmest day the state has seen in awhile. The Storm Prediction Center has already gone ahead with a Level 2 “Slight” risk for parts of Eastern Wyoming and the Nebraska Panhandle.

Heat is the number one fuel for storms and helps to generate instability, especially when there is a good amount of sunshine before storms start to fire up. This looks to be the case in Eastern Wyoming tomorrow ahead of the afternoon hours when storms are expected to begin, likely around 1:00 PM. With the jet stream taking a dip over the region ahead of the weekend additional instability is being brought into the state, raising the chances for strong storms. This will increase the likelihood that strong wind gusts and hail occur with the storms as they move off to the northeast, with some of the hail potentially being large enough to prompt a severe thunderstorm warning (1″ in diameter or greater). Sustained winds with storms could most certainly reach that threshold (58 mph or greater), especially given that a handful of areas could already be seeing sustained speeds over 20 mph thanks to the pattern shift rolling in.

The thing of course that is most concerning however is the potential for a tornado. It isn’t high, but its the highest it has been so far this spring. Winds aloft will be blowing in from the south-southwest, while winds at the surface are expected to be blowing from the south or south-southeast in Eastern Wyoming and the Nebraska Panhandle. This results in a turning of the winds with an increase in height in the atmosphere, and thus raises the chance for rotation and the formation of an isolated tornado. The sustained wind speed of the environment is just as important: strong sustained winds are needed at both levels to generate the rotation. The combination of these factors is known as wind shear. The image below should explain what wind shear is a bit more. The more wind shear there is at the lower levels of the atmosphere, the higher the risk for tornados. Fortunately for Wyoming and Nebraska tomorrow the overall shear looks to be quite low, which will limit the rotation potential. This doesn’t mean that tornadoes will not be possible, however they will likely not be the number one concern; just something to be prepared for just in case.

Wind shear is the change of wind with height in the atmosphere in terms of direction and speed....
Wind shear is the change of wind with height in the atmosphere in terms of direction and speed. The map here shows wind speeds at the 500mb level aloft as well as surface speeds. The higher the number and the more perpendicular the arrows, the higher the shear is. Wind shear values for tomorrow afternoon look to be highest in Northeast Wyoming and the Panhandle of Nebraska, and even higher over in South Dakota. In this image, locations such as Newcastle and Douglas have the most wind shear due to increased surface winds a well as decent change in wind direction with height (arrows pointing towards each other). Meanwhile a place like Casper has no directional shear whatsoever with wind directions being the same at both levels (parallel arrows).(KGWN)

Friday’s severe weather chances will drop back down as temperatures look to drop a bit heading into the weekend. Going through the weekend those powerful Wyoming Winds will become a larger nuisance like during the wintertime months: sustained speeds over 30 mph and gusts likely over 60 mph in many areas of the state.

CHEYENNE, Wyo. (Wyoming News Now) -

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