A BRUSH WITH SEVERE STORMS

1 day ago
3 min read

INTENSE STORMS FOR PARTS OF THE MIDWEST WEDNESDAY

An outbreak of severe thunderstorms is expected from portions of central Illinois into Indiana on Wednesday. Intense tornadoes, swaths of damaging wind gusts to 80 mph and hail greater than 2 inches in diameter is expected. The most significant severe weather should remain just east/southeast of my local area from central Illinois into EC Indiana where a level 4 risk of 5, is currently indicated by the Storm Prediction Center.

SYNOPSIS... (ROUND 1)

To begin Wednesday, a strong mid-level jet streak will overspread parts of the Midwest and lower Great Lakes early Wednesday. Additionally, a deep surface low over the Upper Midwest is forecast to shift southeast across the lower Great Lakes and southern Ontario. It will be accompanied by a strong low-level jet which advects rich surface moisture ahead of a cold front through the evening Wednesday. A warm front, reinforced by morning convection is expected to lift northward into parts of central/northern Illinois. Potent wind fields for this point in June will support a threat for scattered to numerous severe storms . Most of the CAMs (convective allowing models) as well as regional/global guidance, suggests convection will develop over parts of eastern Iowa early Wednesday morning. This activity will quickly shift east through northern/central Illinois into Indiana before noon. A risk for damaging winds will most likely accompany these initial storms. The degree to which this cluster of convection can intensify through mid/late morning remains unclear. However, it appears this first round of morning storms will fairly quickly shift east-southeast weakening with time.

(ROUND 2 SYNOPSIS) AFTERNOON STORMS IN ILLINOIS WITH A TORNADO THREAT.

The more substantial severe threat is expected to develop by early/mid afternoon and depend strongly upon how morning convection evolves spatially. Given the extremely strong moisture advection into the region, it is reasonable to expect an area of rapid airmass recovery from about the Quad Cities vicinity into parts of central Illinois around noon. Storms that form in this environment near the surface low/warm front will likely be discrete and take advantage of strong low-level shear. Large to very-large hail, significant wind gusts, and strong to even intense tornadoes will all be possible.

As you can see on the significant tornado output from the HRRR, the greatest tornado threat should be south of I-80 and mainly southeast of the Quad Cities. The final verdict will be determined by boundaries yet to be established by Wednesday morning's convection.

The simulated radar on the HRRR shows the first wave of morning storms around 9:00am Wednesday.

By late afternoon the HRRR has a line with embedded supercells punching through central and NE Illinois. These have the potential to be severe and tornadic as they intensify east of my area. In fact most of the storms will have cleared my local area by 1-2:00 in the afternoon.

The bottom line is the first wave of storms in the morning will likely be the most widespread in my area but weaker than any that can survive into the afternoon. In other words, the worst of the days severe weather should be just east of my local area.

That said, there will be some strong dynamics and deep moisture for a time early Wednesday which could lead to some intense updrafts and rainfall rates. Many models are suggesting rainfall rates of an inch, perhaps even 2 inches in some spots from the Quad Cites northeast.