Low cloud deck continues over the area with strong northwest winds. A lake breeze front in the north is keeping areas in northern Newton & Jasper County especially cool. Morocco is only 61 & Hebron is at 60.
Temperatures are only in the 60s to near 70 as of 1 p.m. for the viewing area as a whole.
I am still shooting for highs of 67-75.
There have been a few breaks trying to develop in the north & in our southwestern areas, but lack of breaks has led to lack of any destablization & thus lack of any isolated to spotty showers/t'showers developing yet.
Latest high-resolution HRRR data shows clouds breaking up over the couple to few hours with sun appearing & then a couple/few isolated showers/t'showers bubbling up late afternoon-evening. This is due to such cold air aloft & some heating with that strong sun angle near the summer solstice.
Clouds should completely burn off & skies go clear by 10:30 p.m.
Winds will also go calm.
As a result of this, areas of fog may quickly develop & temperatures may tank to 53-57. However, with a southeast to south wind commencing late with the front rapidly coming back north as a warm front, temperatures may then rise to 58-63 & fog disperse some.
Things are getting interesting tomorrow.
A severe MCS should develop & evolve in the Plains tonight & track along & south of the warm front, reaching the Mississippi River by 10 a.m.
MCS should continue to track east, then turn to the southeast, riding the gradient of best instability. This turn is the result of earlier arrival & our airmass not recovering quick enough from the 50s night & cool day today to support a severe MCS with enough CAPE.
So, it will ride where it can get the best CAPE, but still try to stay near the warm front track.
The severe weather risk with it looks to stay just southwest & south of our area.
However, it will have a massive plume of clouds as you can see below, typical of MCSs & MCCs. So, our skies will turn overcast for Friday midday to afternoon with the sun gradually dimming & fading away.
I trimmed highs Friday as a result to 75-81 rather than 77-86.
A period of showers is possible in the 2-5 p.m. time frame as our dew points slowly rise to the lower to middle 60s.
However, along the warm front......behind the MCS.......new, elevated storms should pop after 5 p.m. & line up over the area.
These will occur as the warm front is trying to be thrust & pushed by northward by expanding ridge & heat to the south. This will result in lift. Meanwhile, plume of much more unstable air (from Oklahoma & Missouri) will be pushed up & over a more stable surface, resulting in elevated storms.
Locally-heavy rainfall & isolated hailers are the risks right through the evening hours.
It is a bit unclear about what will transpire after this. All of these elevated storms may form another cold pool & a large MCS & move back south & southwestward, along with another MCS from Iowa to Missouri.
This would occur Friday night to early Saturday morning.
U.S. & Canadian model solutions trend more towards a dry Saturday after this with atmospheric re-charge underway with high/mid clouds thinning here with then hazy sun & cumulus.
However, there are signs that a remnant MCV may be in the area. If the atmosphere can re-charge later Saturday enough after getting working & overturned over a large region Friday, then some storms may re-develop here.
I am currently more inclined to ramp up some storm potential Saturday night as low-level jet strengthens & nudges in with unstable, hot, sultry environment with temperatures of 80-82 & dew points 75-77.
Dew points will finally reach the muggy to oppressive 71-76 range by later Saturday after running 65-70 through much of the day.
I am torn about what to do about Saturday's high temperatures. It will all be dependent on how much cloudiness lingers & what happens with this MCV. I originally went for 85-90 with heat indices reaching 90s to +100 by late in the day.
I am opting to keep status quo, but trim just a hair to 83-90 with heat indices 90s to +100 by late in the day.
Sunday looks very oppressive with highs 87-91 with dew points 75-78, leading to heat indices near 100 to as high as 112.
Looks like any storms Saturday night may last to early Sunday morning, then depart or diminishing as low-level jet decreases & veers.
Sunday looks like the hottest day of 2019 so fair, with temperature (for some) & heat index (for all).
A large MCV & outflow boundary northwest of the area should ignite a line of severe storms in Illinois by afternoon. This should gradually mature into a large MCS with a line of damaging winds on the front of it. This should pass through our area Sunday late afternoon-evening, it appears.
At this point, environment looks characterized by a deep layer of CAPE averaging around 2000 J/kg throughout the column & the CAPE maximizing at up to 3000-3500 J/kg near the surface. Forecast downdraft CAPE of up to 1800 J/kg supports idea of formation of cold pool with ability to form a solid, bowing squall line.
Very high PWATs with water-loaded environment support extremely heavy rainfall rates of 4" per hour. This with the downdraft CAPE also support wet downburst potential, embedded in the MCSs squall line.
Low-level lapse rates of 7.5-8 C/km & up to 7.0 for mid-levels are more than sufficient for storms.
Shear is not impressive with Effective Bulk Shear only forecast at 20-25 kts., but the MCV should easily strengthen it.
Also, in these environments, the thermodynamics are such that they overcome lack of dynamics to support cold-pooling line of storms.
Only flies in the ointment are 1) some outlying data suggesting strong capping trying to take over from hot ridge from the southwest & 2) MCV & triggers not arriving until Sunday night (though that could still support widespread storms, even Sunday night, given the CAPE still available & potential MCV & outflow boundary triggers still around).
Note the projected sounding below for Sunday afternoon-evening below.
Wind vectors are largely the same direction through the entire troposphere for more of a line of storms. Note that they are projected to not be especially strong, but thermodynamics are beyond sufficient. Mechanisms for your cold pool line, wind, wet downbursts are there.
A few storms are possible Monday (as front drops south some), followed by a dry Tuesday, then potentiall an MCS Wednesday. Highs will run 80s Monday-Tuesday & 86-91 Wednesday with heat indices in the 90s to +100.
Thursday & Friday of next week looks dry & a bit less humid with highs 78-85 & lows 57-65.
It will turn hot & humid as we exit June & move into early July with highs rising to 89-93 with heat indices near 100 to 112.
Some rounds of storms with some severe risk are possible in the July 4-6 time frame.
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- June 24, 5 PM Weather Forecast Update