Tornado, Damaging Wind Risk in Illinois and Indiana Today

Classic clash of the air masses today as warm and humid air surges northward into the Midwest, with bitterly cold Arctic air blasting across the Dakotas. The result will be a dynamic, high impact storm system with blizzard and winter storm conditions across the Upper Midwest and Great Lakes, with a springlike severe weather setup in the warm sector across portions of Illinois and Indiana.

The severe risk across Illinois and Indiana comes in two distinct rounds. First, as the warm front lifts north a few intense storms may produce hail generally near I-80 across north-central Illinois, moving into northeast Illinois and eventually northern Indiana mid to late Sunday morning. These storms and their hail risk may even make it into southern Michigan by mid-day.

As warm and humid air surges north a few intense storms may produce hail from northern Illinois into northern Indiana, and perhaps southern MIchigan late morning through mid-day.

The potentially more robust and higher impact round of severe storms accompanies the area of low pressure and cold front as it moves east into eastern Illinois, approaching the Indiana border mid afternoon into the evening hours. If we were looking at a better aligned surface low with southerly surface winds, I think we'd be looking at a tornado outbreak across eastern Illinois into Indiana later today. You've got really anomalously high moisture with dew points in the low 60s, and a 110 knot jet stream at 500 mb screaming overhead. Show me just dew points and H5 winds today and I'm super concerned.

A potent jet stream wave like this is often synonymous with severe weather outbreaks, especially when paired with anomalously deep moisture.

As it is, surface winds out of the south-southwest may still allow just enough of a "hump" in the low-level hodograph to allow for a couple of supercells with an associated tornado risk ahead of the cold front, that is unless they're right up against the Arctic cold front blasting in from the east.

High-resolution guidance is increasingly showing a volatile environment and a few robust storms developing near the Illinois and Indiana border on Sunday afternoon/evening.

Less than perfect surface winds and a strongly forced cold front might make this lean linear with a predominant wind damage risk, but there's just enough to make me go "hmmm" here and think either a kinky line with embedded tornadoes or at least one or two supercells ahead of the cold front might be possible.

Here's what the Storm Prediction Center has to say in their latest outlook which upgraded the Illinois/Indiana border to slight risk / level 2 out of 5:

WATER-VAPOR IMAGERY THIS MORNING SHOWS A MID-LEVEL LOW NEAR THE  MT/ND BORDER WITH A TROUGH INTO THE CENTRAL ROCKIES/SANGRE DE  CRISTOS.  THIS MID-LEVEL LOW WILL MOVE INTO THE CENTRAL GREAT LAKES  BY EARLY MONDAY MORNING.  STRONG SOUTHWESTERLY 500-MB FLOW (80 KT)  EXTENDING FROM THE BASE OF THE TROUGH THROUGH THE LOWER MO VALLEY  AND OH VALLEY WILL FEATURE AN INTENSIFYING 110-KT JET REACHING THE  MO-IL BORDER THIS EVENING BEFORE FURTHER STRENGTHENING TO 130 KT  OVER OH BY THE END OF THE PERIOD.      A SURFACE LOW OVER EASTERN KS WILL DEEPEN RAPIDLY THROUGH TONIGHT AS  IT MOVES TO LAKE HURON.  A FRONTAL ZONE EXTENDING EAST-NORTHEAST  THROUGH THE SOUTHERN GREAT LAKES THIS MORNING WILL SERVE AS THE  NORTHERN EDGE OF THE MOIST SECTOR.  A COLD FRONT INITIALLY OVER  KS-OK WILL SURGE SOUTH-EAST.  SOUTHERLY LOW-LEVEL FLOW ACROSS THE  MOIST SECTOR WILL MAINTAIN A FETCH OF SEASONABLY HIGH 58-62 DEG F  DEWPOINTS IMMEDIATELY AHEAD OF THE FRONT/LOW.     A RAIN SHIELD WITH EMBEDDED THUNDERSTORMS THIS MORNING FROM NORTHERN  MO INTO THE SOUTHERN GREAT LAKES COULD FEATURE A STRONGER STORM OR  TWO THROUGH MIDDAY, BUT THE PRIMARY SEVERE RISK WILL LIKELY FOCUS  THIS AFTERNOON THROUGH TONIGHT.  MODEL GUIDANCE INDICATES THE CAP  WILL ERODE NEAR THE EVOLVING TRIPLE POINT AND COLD FRONT BY MID-LATE  AFTERNOON.  UPWARDS OF 500-1000 J/KG MLCAPE IS POSSIBLE ACROSS PARTS  OF CENTRAL INTO EASTERN IL WITH BUOYANCY TAPERING WITH EAST EXTENT  ACROSS THE OH VALLEY.  A SOUTHWARD-DEVELOPING CONVECTIVE BAND IS  FORECAST TO EVOLVE LATE THIS AFTERNOON THROUGH THE EARLY EVENING.   LONG HODOGRAPHS AND STRONG 2-3 KM FLOW WILL FAVOR A RISK FOR SEVERE  GUSTS WITH THE MORE INTENSE STORMS AND SURGES WITH THE MATURING  BAND.  MODELS INDICATE THE WIND-DAMAGE THREAT MAY PERSIST ACROSS THE  OH VALLEY/SOUTHERN GREAT LAKES TONIGHT DESPITE MEAGER INSTABILITY.   THE TORNADO RISK APPEARS HIGHEST WITH CELLS THAT CAN DEVELOP NEAR  THE INSTABILITY AXIS AND MATURE BEFORE EITHER DESTRUCTIVE  INTERFERENCE OF THE LARGER-SCALE COLD POOL OVERWHELMS CELLULAR MODE,  AND/OR THIS ACTIVITY MOVES FARTHER EAST INTO LESSENING INSTABILITY.