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THE BEAT GOES ON...

With a mid-summer heat dome in place, the beat went on for our steamy and at times stormy weather pattern Tuesday. As far as heat goes, Tuesday was the worst of summer so far with dew points in the mid to upper 70s and highs reaching well into the 90s. Heat index values up to 105 were common with some local spots tapping out greater than 110. In Oskaloosa, Iowa, the ASOS observation at 3:00pm. showed a 100 degree temperature with a dew point of 78. That generated a searing 118 degree heat index.

A number of places in southeast Iowa came very close to reaching the century mark. Some NWS reported highs.

WASHINGTON.....99

FT. MADISON......99

KEOKUK..............99

MT. PLEASANT...99

MUSCATINE........99

VINTON................98

BURLINGTON......97

IOWA CITY...........97

Moline..................97


Here's the upper air pattern at 500mb responsible for the oppressive conditions. The heat ridge is centered over Arkansas with heat and humidity on the NW fringe aimed directly at Iowa.

Under the ridge, where the air is compressed it sinks and heats up. As a result heat advisories and warnings were posted from Iowa to Louisiana.

Here's some of the heat index values reported around 2:00pm Tuesday. There's a 109 showing at the Quad City Airport in Moline.

WHAT'S NEXT...

Wednesday's weather will be heavily reliant on Tuesday night's convection. A forward propagating thunderstorm complex known as an MCS advanced rapidly through my region Tuesday evening. It generated a significant cold pool that drove storms southeast of the region shortly after midnight. Rain cooled air (or at least cool outflow) will keep temperatures lower in the northern half of the region. Further south, how far the cool air can penetrate is in doubt and Wednesday is likely to be another toasty day here. The EURO is indicating highs that look like this. In most areas they are down 8-10 degrees signifying the end is here (or coming) for this round of heat. If heat advisories are issued Wednesday, they would likely be for the area near and south of HWY 34.

With far less instability Wednesday and subsidence kicking in, models are not at all excited about rainfall or severe weather prospects. At this point, SPC only indicates a marginal risk of severe storms near and south of I-80..