Thunderstorms developed across western Nebraska and moved into south central Nebraska Monday evening and night. Damaging thunderstorm wind gusts were the most common hazard from the storms, although large hail was also reported. As the storms weakened, heat bursts developed, which caused temperatures to jump to the upper 70s to near 80 degrees, and the wind to gust to 40-60 mph.
Heat bursts are caused by decaying thunderstorms and develop in a unique environment. The setup for a heat burst requires dry air directly beneath a weakening elevated thunderstorm. When a thunderstorm is weakening, air within the thunderstorm begins to sink. If the sinking air is very dry and high enough, it will begin to accelerate toward the ground since it is more dense. Any remaining precipitation will fall through the dry air and evaporate. As the air continues downward, it warms rapidly due to compression.
The following image depicts the temperature and relative humidity profile at the Regional Airport in Grand Island, NE. As the rain arrived, the relative humidity increased, and then the relative humidity dropped, and the temperature rose with the heat burst which occurred shortly after 2 am CDT (0702 UTC). The graphic is courtesy of MesoWest.
Preliminary storm reports from Monday evening and night are listed below.
.TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON