Fri-Sat, Dec 10-11 Severe T'Storm And High Wind Episode Update #1

(11:45AM - 12/9/21) A storm system moving through the region will bring severe t'storm and high wind potential to portions of the state, Friday afternoon through Saturday afternoon.

Summary...
A storm system will move from the Plains on Friday into the Great Lakes on Saturday. This storm system will bring severe t'storm potential to Central and Southern Illinois Friday afternoon through early Saturday morning, and high wind potential to much of the state Friday night through Saturday afternoon.

With this update we have pulled severe t'storm probabilities a bit further north across the state, and have introduced a level 3 severe t'storm risk across Southern Illinois. These changes we based on a slightly further north track int he storm system, as shown on model guidance the past 24 hours. No changes were needed to the previous high wind forecast.

​Forecast...
Severe T'Storm Potential...
A strong storm system and associated cold front will push across the state, Friday evening through Saturday morning. Along and ahead of this cold front, a few rounds scattered showers and t'storms will develop across Illinois, Missouri and Arkansas Friday afternoon and evening. This activity will then push northeastward, moving across Central and Southern Illinois Friday afternoon and evening through early Saturday morning. Ahead of this activity, the environment across Central and especially Southern Illinois will be supportive of some severe t'storm threat. This environment will feature low instability of 250-,250J/KG, dew points in the mid 50's to mid 60's, strong forcing, high shear and lapse rates of 4.5-6.5C. This environment will be supportive of upwards of a level 1/isolated to level 3/scattered severe t'storm risk across Central and Southern Illinois. Damaging winds, isolated tornadoes and small hail will be the severe weather threats.

High Wind Potential...
A storm system moving through the region Friday and Saturday will bring a period of high winds to a large portion of the state, this Friday night through Saturday afternoon. The combination of the following will lead to the period of high winds... An amplifying/phasing disturbance, strengthening/deepening storm system, strong pressure rise couplet and strengthening jet with high winds aloft. Wind gusts of 35-50MPH will be likely Friday night through Saturday afternoon across much of the state.

​Below are the severe t'storm and high wind forecasts for this event.

JP