© 2019 Terry Swails

SUMMER TO FLEX ITS MUSCLES WITH EXCESSIVE HEAT...

July 16, 2019

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

Sunday highs and heat index

This comes after a two week period where temperatures have already been above normal over most of the central Midwest.

Rain has also become scattered and sparse. Here's the 7 day totals. Most of my central and southern counties have seen no measurable rain. The warmth and dry conditions have really burned the grass. Lots of sprinklers running in my neighborhood. 

The big questions going forward is when does the heat break and when does the rain return? Regarding the heat it looks like a front will arrive sometime late in the weekend with cooler, drier air. The GFS has it through Saturday night while the EURO is more than a day later...probably more realistic. Whatever the case you can see the EURO gets the job done by Tuesday of next week.

As for rain, the next 2 nights could see some storms over northern Iowa, southern Minnesota, and Wisconsin. However, the rest of the area looks capped as warm temperatures aloft suppress storm development. The 10 day rainfall forecast is feast or famine with much of my area going hungry is the EURO is correct.

Here are the 10 day rainfall departures. 

The Weather Prediction Center also sees the dry weather continuing into late July. Here's the 6-10 day outlook from WPC.

And the 8-14 day outlook.

 

Getting back to the real concern of excessive heat, Tuesday looks to be the last tolerable day before it builds, expands, and becomes an issue. Time for summer to flex its muscles! Stay cool and roll weather...TS 

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