Heat indices in our southwestern areas have reached the mid 90s today! Highs have reached upper 80s there with mid 80s into the heart of the area.
The highest dew point & heat index of 2019 was reached here at the station with 72 & 91, respectively with a high of 85.
Outflow boundary from morning storms is growing more diffuse & tending to merge with the warm front, while the warm front lifts northward, separating 80s to near 90 from 70s.
We had a supercell storm with high winds, large hail & off & on tornadoes & funnel clouds in central Illinois. There were even a few cells around Champaign. These have tended to occur at & near the intersection of the outflow boundary & warm front.
They have all completely collapsed due to warm, dry layer lid or cap overspread the area & sealing the troposphere off at about 8,000'. This hot, dry air is emanating from upper ridging in the southeastern U.S. where widespread record heat is developing. Highs today were near 100 from North Carolina to Georgia & Florida with developing wildfires & greatly-worsening drought. Highs of 98-105 are likely for the next at least 7 days across the South with upper 90s even to Virginia.
This warm layer is preventing any new storm development along these boundaries despite an unstable, juicy airmass & lots of directional & speed shear for severe weather. The shear is quite pronounced along the boundaries in the lowest 6,000'. This, along with the moist, unstable boundary layer with pretty low LCLs is suitable for tornadoes for storms that really go.
The cap may erode some in the far northwest this evening (Newton, Jasper, Benton, Pulaski counties). This should allow some storms to pop & reach that area in the 8:30p to around midnight time frame with severe weather risk (wind, hail, tornado risk all on the table).
We will monitor closely for any tweaks to tracking &/or timing or if the cap ends up holding, preventing any storm development there.
Latest HRRR model is indicative of cap erosion & flare-up of some supercells this evening that impact the northwest.
Line of severe storms around Chicago area tonight should race into Michigan & collapse, but an outflow boundary from these storms will surge southeastward into our area.
The boundary should be Logansport to Fowler, roughly, at 10 a.m. Saturday morning.
Outflow boundary may flare a few storms (with severe risk) in the area Saturday afternoon-evening with 35% coverage.
Boundary will surge back northward & storms may shut off tomorrow night.
Storms should re-form on boundary as cold front approaches late Saturday night-early Sunday morning.
This line of storms should pass Sunday morning, followed by just a period of plain rain up to the afternoon with temperatures 67-72.
Note the storm & rainfall action hugging the heart & areas northward around Indianapolis. This will be right on the edge of the outflow boundary from our storms.
Note what happens mid afternoon to evening. Our rainfall ends, but the outflow boundary, merging with the cold front pops new storms around Indianapolis.
So, looks like some rain & lightning risk late morning to early afternoon, then break, then rain & lightning risk in Indy mid-afternoon to evening with a narrow (perhaps roughly 2 hour) break in-between
Front moves back north on Memorial Day, bathing us back in warmth & mugginess. Highs should run 80 northeast to 88 southwest with around 83 for Greater Lafayette. Heat indices will run 84 to 92 over the viewing area from northeast to southwest.
A couple isolated storms are possible along & just north of the warm front as it passes northeastward through the viewing area.
Tuesday looks completely dry, very warm to hot, humid, windy & highs 85-90 with heat indices 90-96.
Line of storms with severe weather risk is possible Wednesday, followed by dry, cooler & less humid weather Thursday & Friday with highs in the 70s & lows in the 50s.
It should heat up again & turn humid next weekend & beyond with storms possible with some severe risk around June 2 & June 10.