SUMMER TO FLEX ITS MUSCLES WITH EXCESSIVE HEAT...
The heat is on around the Midwest and it's going to get worse before it gets better. Due to that fact the NWS has issued an excessive heat watch for my area Wednesday afternoon through Saturday evening.
The screaming message is to prepare for a prolonged period of peak heat indices between 100-110 F with little relief expected at night due to heat indices not falling below the mid 70s to lower 80s. Later Tuesday the NWS will decide whether to upgrade the watch to an advisory or warning. Warning criteria is two consecutive days with peak heat indices of 105 F or four consecutive days at or above 100 F. Whatever happens in that regard it's not going to be pleasant.
All models are in good agreement on the strengthening upper level ridge over the Central U.S. and an eastward surge of some very warm temperatures aloft.
850 temperatures near 26 C at the end of the week are 2-2.5 standard deviations above the mean for July and have a return interval of once every 5-10 years. Mixing of this anomalously warm air aloft to the surface, combined with periods of sun, will push max temps well into the 90s, and possibly near 100 F for a few days. The hottest days will likely be Thursday - Saturday.
The EURO is the hottest model with several days of high temps of 95 to 100 F for most of the region with no break until next Monday. Here's the highs and heat index values on the EURO when the heat is at maximum capacity...maybe 2-3 degrees too warm.
Thursday highs and heat index
Friday highs and heat index
Saturday highs and heat index