The Storm Prediction Center has issued a convective outlook for tomorrow, November 5th, 2017. This outlook shows the potential for quite a wide area being impacted by possible severe weather. “Severe thunderstorms, capable of large hail, damaging winds, and a couple tornadoes, will be possible from parts of the mid Mississippi Valley eastward to the lower Great Lakes Sunday into early Sunday night.” (SPC Summary) Central Illinois through Western Ohio is the area of the most concern. This region has been placed under an enhanced risk for severe weather (Risk level 3/5.)
Setup For Severe Weather
Earlier in the day, a surface cold front will stretch from the Kansas area into East Illinois/North Indiana. As it approaches this region it transitions into a stationary/warm front. Some morning cloud cover/precipitation may bolster the cold sector to the North of the stationary/warm front. Coupled with morning cloud cover/precipitation in the warm sector, could result in weakened instability development and low level heating. Also, there is a lack of a strong surface cyclone, so backing of winds will be not be considerable.
Some weak shear impulses should initiate storms in the eastern Missouri to western Illinois region in the afternoon. Furthermore, the formation of the storms is expected to be in smaller bowing segments with some rotating updrafts embedded within. These storms with embedded rotating updrafts will form mostly in Illinois and Indiana. Additionally, strong shear is expected resulting in some concern for very large hail. As the cells accelerate east/northeast due to small scale bowing, damaging winds will become the primary concern.
“Without both more substantial cyclogenesis and surface destabilization, the tornado threat remains uncertain, as both storm
mode and an undercutting front should temper the threat. However, the magnitude of low-level shear may favor occasional low-level mesocyclones embedded within any short bowing segments, primarily across Illinois and Indiana. As such, a couple tornadoes remain possible, especially where surface winds can back slightly ahead of a weak frontal wave.” (SPC)
This is stating the tornado threat is unknown at the time, but that the potential is most certainly there. This is shown in the Probabilistic Day 2 Outlook. A region is shown with a 30% probability with hatched lines drawn over the enhanced threat region through Illinois and Indiana. This region is the most likely to experience tornado development with the potential for some isolated tornadoes elsewhere. Remember to always take shelter if there is a tornado siren going off. Always remember: Things can be replaced, lives cannot.