Tuesday promises to be a burner around the central Midwest as some good old fashioned heat and humidity engulfs the central Midwest....corn growing weather to be sure!
HEAT INDEX VALUES
The big story today will be the combination of heat and moisture that leads to heat index values in the mid to upper 90s. Easily the muggiest day of the year to date..
Models have been pretty aggressive showing dew points in the low to mid 70s. I have serious reservations about levels getting that high. I'm thinking more like 70.
The 3k NAM and most other models keep highs in the mid to upper 80s.
STRONG STORM CHANCES
You will notice dew points and temperatures in Minnesota are considerably cooler. That's behind a a cool front that makes inroads into my northern counties. That's the forcing that will bring the next round of showers and thunderstorms to at least my northern counties Tuesday night. You can see there is some very robust instability ahead of the front towards evening with hefty CAPE values from northern Iowa into southern Wisconsin and Minnesota.
In most areas a stout cap will keep storms at bay. However, the convective models do pop storms just north of the Iowa border towards evening. Here's the simulated radar on the 3K at 7:00 pm Tuesday.
Assuming storms do develop there will be a window for severe weather over northern Iowa and points just north Tuesday evening. The tornado threat looks low but gusty winds, some hail, and heavy downpours are a real possibility, especially north of HWY 20. This is the risk outlook for strong storms from the Storm Prediction Center. Tuesday.
The southern extent of the storms diving deeper into Iowa and Illinois Tuesday night will be determined by the depth of the cold pool that develops with the budding convection. If it's large in scope, it could create enough outflow to push the storms and boundary further south into the rest of my area late evening or overnight. By then the threat of severe weather should be largely diminished. We won't know for sure though until we see how things develop Tuesday afternoon.
The front sinks southward out of my southern counties by Wednesday evening. Before that happens scattered thunderstorms are possible Wednesday, especially south of I-80. These should exit the far south in the evening and after that rain chances look low until a back door front plunges south late Thursday night or early Friday. Right now models are not very bullish with storms attending the frontal passage. After tit departs, cooler drier air returns for the weekend which allows for pleasant weather conditions.
In general, the extended heat that had been advertised by many sources the past 4 or 5 days, never really materializes. In fact, Tuesday will be the only day of the week where heat becomes a real issue. This pull back from significant prolonged heat is something I was concerned about last week due to a pattern that is prime for back door cold fronts owing to a deep eastern trough. This type of upper air flow does allow for short warm-ups that are followed by pleasant cool-downs. I expect another warm-up early next week but nothing that looks prolonged. It will be interesting to see if this is a preview of the overall summer pattern ahead of us.
That is all for now. Keep your cool today and as always, roll weather...TS