Areas of Heavy Rainfall, Then Highest Heat Indices of Summer Possible Late Next Week

After Periods of Rain & Storms, But Cooler (Still Muggy) Weather, The Groundwork Will Be Laid for the Highest Dew Points of the Summer Late Next Week (80 Possible) with Dangerous Heat Indices

Posted: Jun. 21, 2018 4:57 PM
Updated: Jun. 21, 2018 5:08 PM

TODAY-FRIDAY:
Bands of heavy rainfall with a few embedded t'storms have been pivoting through the area all day.  Some localized areas have received +4" of rainfall, which as led to flash flooding.  In fact, Areal Flood Warnings are up for part of the evening for Carroll, Clinton & Howard counties.

The sun has randomly poked through in areas this afternoon between rainfall, but the bulk of the sun out is in the southwestern half of the area as of 4:21 p.m.  This sunshine extends into Illinois, which has resulted in a line/band of storms to develop, which is racing east & northeastward towards our area.  Other random showers & t'storms are also popping in the sunshine in the southwest half & moving east & northeastward.  This rainfall will impact the entire area this evening as the line/band pivots through.  An isolated severe storm or two cannot completely be ruled out & local flash flooding is possible.

The rainfall will tend to decrease tonight to just spotty showers (lows 64-68), but new scattered showers & t'storms will bubble up tomorrow.  Low clouds will give way to big, towers of cumulus, resulting in locally-heavy, flash flood-producing downpours.  An isolates severe storm is possible.  It will still be muggy with highs 77-82.  Although the rainfall will not be as widespread as today (coverage 90% on average), it will still reach around an average of 55%.

FRIDAY NIGHT-SUNDAY:
Rainfall will tend to taper tomorrow night with some patchy fog developing with low clouds.  However, the low clouds should break again for a mix of clouds & sun Saturday.  Spotty showers/t'showers should bubble up with muggy dew points & highs of 77-82 after 63-66 in the morning.

Sunday should feature some patchy fog & low clouds in the morning, followed by sun & clouds.  A few spotty showers/t'showers are possible with the muggy conditions with highs 82-85.  It appears that any organized severe risk (with look like it might get in here late in the weekend) would tend to set up to our southwest & south. 

Multiple complexes of severe storms (MCSs) in the Plains will occur in the weekend & one of these will produce what is called an MCV.  In many instances, these large complexes of storms, often driven/maintained by the nocturnal low-level jet in the Plains (ribbon of fast-moving air at around 5,000' from the Gulf of Mexico that is pulled into the Plains by difference in cooling between the drier Rockies/High Plains & eastern, more moist Plains.  There is so much rising air motion over a large area feeding these that the surface pressure drops & you get a meso-low or vortex to form or an MCV.  These "leftovers" of a big storm complex overnight often move east & if it gets hot & unstable, produce storms (some severe) in our area. 

One of these MCVs will pivot into Missouri & southern Illinois/Indiana to Tennessee Sunday.  This could pop a new complex of storms.  At this point, again, main threat is southwest & south of here, but we will monitor.  Still those spotty showers/storms will tend to pop here.

MONDAY-TUESDAY:
As for Monday & Tuesday, they look dry with sunshine, but Tuesday looks more humid than Monday.  Monday may actually feel okay even though it will still run for a high of 83-88.  Tuesday highs will run 85-90.

WEDNESDAY-FRIDAY:
Wednesday-Friday of next week gets interesting.  Given all of the wet ground & lush corn/soybeans & overall vegetation across the entire region from the rainfall, VERY high dew points are likely to pool from central Illinois to Indiana.  Dew points may reach 80.  This, combined with expanding upper ridging & intense heat & the set-up is there for a dangerous heat event.  Highs of 89-94 are likely with dew points 76-81, resulting in heat indices of 103-109.

On the edge of this intensifying heat, a cluster/complex of storms may affect us Wednesday evening/night with some severe risk, perhaps.  A cluster of storms is possible Thursday & perhaps another Friday.  Wednesday looks like the largest one, the others look smaller in size.  However, given such high heat/dew points, surface instability will be high, resulting in the potential of really strong updrafts.  So, any of the days have the potential for some severe weather.  Looks more wind threat Wednesday & wind/hail Thursday-Friday with local flooding threat throughout.

High moisture/dew points & persistent southerly/southwesterly winds will keep it very warm at night with lows not dropping below the mid 70s in many areas.

TO THE BEGINNING OF JULY:
The high humidity & heat may linger right into the beginning of July with a few bouts of storms & occasional small waxes & wanes in the dew points/temps.  However, the overall pattern will feature lots of heat & humidity.  Get ready!

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Fall-like temperatures on the horizon
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