(12:30PM - 6/19/21) A storm system will move through the region on Sunday, bringing a severe t'storm risk to a large portion of the state Sunday afternoon through Sunday night.
A storm system will move across the Plains Saturday night, through the Midwest and Great Lakes on Sunday, and to into the Northeast by Monday. This storm system will bring a severe t'storm risk to a large portion of the state for Sunday afternoon through Sunday night. Model guidance has been showing this potential for a few day now, and continues to be in fairly good agreement regarding this event. With this update we have upgraded severe t'storm probabilities to a level 3 severe t'storm threat across portions of Northern and Central Illinois, as confidence is increasing.
Sunday Afternoon-Sunday Night...
A lead disturbance is expected to move from Iowa and Missouri Sunday morning, across Illinois Sunday afternoon, and then into Michigan Sunday night. The regeneration and development of t'storms associated with this disturbance is likely across Eastern Iowa and Northern Illinois Sunday afternoon. This activity will then spread eastward across Northern Illinois Sunday afternoon. Further west along the cold front and along any potential outflow boundary from early activity, additional showers and t'storms will develop Sunday afternoon across Iowa and Northwest/Western Illinois. This activity will spread eastward across a large portion of the state, late Sunday afternoon through Sunday night. An environment supportive of a severe t'storm threat will be in place. This environment will feature moderate to high instability of 2,500-4,000J/KG, dew points in the mid 60's to mid 70's, high shear and strong forcing. This environment will be supportive of upwards of a widely scattered to scattered severe t'storm risk (level 2-3) across much of Northern and Central Illinois. Damaging winds, large hail and a few tornadoes will be the main severe weather threats.