Storms today will support large hail if they can fire
MANKATO, Minn. (KEYC) - The Storm Prediction center has south/southeastern Minnesota and parts of northeast Iowa and southwest Wisconsin under a slight risk for severe weather for today, July 27th, 2021. Storms that do turn severe today will have a main threat of large hail and some gusty winds if they can fire.
Instability will not be a concern for this afternoon as forecast models are showing both surface based CAPE and mixed layer CAPE Values between 3000-4000 J/kg. Those values indicate strong updrafts capabler supporting large hail and strong wind gust.
Vertical speed shear will not be a problem either. Shear will allow for storms to maintain a long lasting and healthy updraft. Directional shear is lacking for the development of rotating updrafts so the threat of tornadoes does not exist for this evening.
The one concern is going to be the forcing. Current observations note a stationary front across parts of southern Minnesota this afternoon. Storms that rolled through southeastern Minnesota and western Wisconsin have produced some cold outflow. These two boundaries will be the possible lift for this evenings storms. Questions remain how far west the cold outflow will drift and how strong of a sourcing the stationary front will have.
The slight risk was updated this afternoon and shows a trend east due to this morning’s convection being further east than model projections. This afternoon thunderstorms are ongoing near the La Crosse area more storms expected to fire around 5 to 6 PM this evening based on model guidance. Forecast models do not handle cold outflow boundaries well so we will have to see how things play out the rest of this afternoon going into this evening. Rain and storm chances continue to dwindle for areas west of I-90.
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