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June 20th, 2021 Severe Weather Event


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16 minutes ago, CheeselandSkies said:

Easy no-chase decision for me, then.

Sent from my Pixel 4a using Tapatalk
 

Ha, well, don't base your decision off of my post.  When I was looking at the CAM progs, I was thinking what does this appearance remind me of, and 6/30/14 was one that came to mind.  There was uncertainty about what that second wave of convection would do as it moved east, and it ended up being a prolific QLCS tornado producer south of Chicago.

14jun30_Zloop_40.gif.dec3a1c8150c308359ac40447f30d4e8.gif

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Feel free to give advice, I think I'm gonna head south westish for now

Edit: Ripping off Chicago Storm's comment, we're going to Pontiac. His advice got me within ten miles of a tornado last time that I missed because I stopped for gas, so I'm gonna follow his advice again.

 

 

 

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28 minutes ago, Malacka11 said:

Feel free to give advice, I think I'm gonna head south westish for now

Edit: Ripping off Chicago Storm's comment, we're going to Pontiac. His advice got me within ten miles of a tornado last time that I missed because I stopped for gas, so I'm gonna follow his advice again.

 

 

 

Fill up now. That's my advice for the day :D

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37 minutes ago, janetjanet998 said:

For some reason the developing convection in MO that the meso was issued for turned into a moderate rain blob

what a waste of a 60kt 500mb speed max so far

 

sometimes mini discrete storms can develop within this but so far nothing

Still a bit of inhibition in that area.  But look just behind it at some cells forming with lightning near the MS river.

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Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
204 PM CDT Sun Jun 20 2021

.MESOSCALE DISCUSSION...
203 PM CDT

The MCV we have been monitoring since daybreak is struggling to
maintain a consistent footprint of deep convection as it enters
west- central Illinois early this afternoon. Even with these radar
trends, conditions continue to destabilize south of the warm
front, which is now analyzed to be roughly from northern La Salle
County eastward between I-80 and I-88 into extreme northwest
Indiana. Deep-layer shear of 40kt+ remains present with 50-60kt of
mid-level flow per KLOT VWP.

The lack of increasing convection suggests low-level capping may
be a little more robust that previously thought, likely owing to
slower heating from the cirrus canopy filtering overhead since
this morning. With this complex mesoscale set-up, CAMs
unsurprisingly continue to struggle. However, the trend of hourly
CAMs to quickly re-develop convection as the MCV enters the CWA is
entirely plausible if the CAP is indeed taking longer to erode.

We now have to focus on the prospect that the afternoon
convection does not fully materialize and determine the
implications as we move into this evening. With minimal convection
this afternoon, the low- level air mass should quickly recover on
a developing 50kt+ LLJ. So, round two of potential severe
convection along the cold front mid to late evening is still in
play, with pockets of damaging winds and perhaps embedded QLCS
tornadoes near and south of the warm front.

Kluber
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Area just W/SW of RFD is one to watch for initiation. Warm front is through ORD and will stall w the lake breeze. Low level flow is strongest near RFD ahead of a weak surface meso low. It’s a pretty small area but there is just enough overlay of instability and low-mid level is enhanced flow from the MCVs to get it going. Shame it’s so cloud my but that will also keep LCLs lower. 

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Hoping all the cloud cover from the weakening rain to the NW hasn't ruined it altogether. Definitely not falling in line with SPC's original timing. Reed Timmer stated this morning that things didn't look as promising in Eastern IA and IL and opted not to chase.

 

MD 1035 graphic

 

Mesoscale Discussion 1035
   NWS Storm Prediction Center Norman OK
   0202 PM CDT Sun Jun 20 2021

   Areas affected...Southern Iowa...northern Missouri...and northeast
   Kansas

   Concerning...Severe potential...Watch possible 

   Valid 201902Z - 202100Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Scattered strong to severe thunderstorms may develop along
   a southeastward moving cold front by the mid afternoon hours. The
   strongest storms may pose a severe hail and damaging wind risk. A
   watch is possible.

   DISCUSSION...Latest GOES visible imagery shows a growing field of
   cumulus along the southern IA/NE border in the vicinity of a cold
   front and nearby surface trough (with a shallower field noted along
   the front stretching back to the southwest into northern KS). The
   cumulus along the IA/NE border have taken on more agitated
   characteristics with some vertical development noted in the past
   30-60 minutes. Modified morning soundings, as well as RAP forecast
   soundings and mesoanalysis estimates, suggest that MLCIN is waning
   as temperatures climb into the upper 80s with upper 60s/low 70s
   dewpoints. These trends suggests that convective initiation is
   possible in the coming hours (likely by mid afternoon) - initially
   within the IA/NE cumulus field and then possibly along the cold
   front to the southwest. 

   A favorable parameter space just ahead of the cold front (1000-2000
   J/kg MLCAPE and 40-45 knots of effective bulk shear) should support
   strong convection. Deep-layer flow oriented nearly orthogonal to the
   cold front may support initially discrete to semi-discrete modes
   that may pose a hail/wind threat. However, slightly cooler/stable
   outflow from prior convection across northern MO/southern IA and
   increasing inhibition southwestward into KS introduce some
   uncertainty into the spatial extent of the threat. Air mass recovery
   trends across northern MO/southern IA will continue to be monitored
   and a watch is possible in the coming hours.

   ..Moore/Hart.. 06/20/2021
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Area Forecast Discussion
National Weather Service Lincoln IL
244 PM CDT Sun Jun 20 2021

.SYNOPSIS...
Issued at 244 PM CDT Sun Jun 20 2021

A strong cold front will push into the region from the northwest
tonight. Strong to severe storms are possible ahead of the front,
into tonight. Scattered showers and a few storms will linger
behind the front on Monday, along with much cooler temperatures.

&&

.SHORT TERM...(This evening through Monday)
ISSUED AT 244 PM CDT Sun Jun 20 2021

Complex of storms has weakened as it pushed into western IL early
this afternoon. 19z ILX sounding indicated a layer of warm air
centered at 850 mb, providing a significant cap for deeper
convective development. Besides the cap, the atmosphere is
supportive of robust convection given 60 kt winds at 500 mb and
mid level lapse rates at 7C/km. Latest forecast soundings and SPC
mesoanalysis show a weaker cap over eastern IL, which could be
eroded from outflow moving in from the west. Latest hi-res
visibile satellite imagery shows modest cu development east of
I-57. This will be the area to watch over the next few hours, and
the last few runs of the HRRR have shown discrete convection here
between 21-00z. All severe modes would be possible given nearly 3k
J/kg MLCAPE and strong deep layer shear near 50kt, but with the
warm front located farther north near I-80, damaging winds and
hail are primary threats.

A line of thunderstorms is expected to develop ahead of a cold
front across eastern Iowa early this evening, then push into the
northwest CWA towards mid evening. Severe storms are possible
given moderate instability and favorable deep layer shear.
Damaging winds gusts are the primary threat, with hail and an
isolated QLCS tornado possible. A localized flash flood threat
exists due to high rainfall rates when PWs peak over 1.75" this
evening. As the line shifts farther southeast into central IL near
I-55 towards midnight, conditions become less favorable for both
severe and flash flooding with decreasing instability. The
weakening trend continues overnight with diminishing storm
coverage expected near and south of I-70 late. Southwest gradient
winds gusting over 20 mph ahead of the front this evening, will
veer west northwest post frontal late tonight, also gusting over
20 mph.
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Feel free to give advice, I think I'm gonna head south westish for now
Edit: Ripping off Chicago Storm's comment, we're going to Pontiac. His advice got me within ten miles of a tornado last time that I missed because I stopped for gas, so I'm gonna follow his advice again.
 
 
 

I didn’t even follow my advice. Got off work at 2, got home and haven’t left.

19z ILX sounding has a sizable cap, dry air aloft, among other things. Maybe the MCV will eventually do something in IN/OH, but IL is mostly done for.

Attention then turns to the front in IA, but the issue there is the best threat will likely be confined to IA. Modified flow in off the backside of the first waves activity is feeding northwest, so the corridor of max potential out there is likely only in C IA.

All in all, no bueno.


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   Mesoscale Discussion 1036
   NWS Storm Prediction Center Norman OK
   0325 PM CDT Sun Jun 20 2021

   Areas affected...Portions of eastern Illinois and northern Indiana

   Concerning...Severe potential...Watch possible 

   Valid 202025Z - 202230Z

   Probability of Watch Issuance...60 percent

   SUMMARY...There is an increasing severe weather threat late this
   afternoon and into the evening from east-central Illinois into
   northern Indiana.

   DISCUSSION...An MCV has traversed northern Missouri and western
   Illinois through the morning and early afternoon today. The
   convection has been mostly weak, likely due to the stable, capped
   downstream airmass from the overnight MCS in the region. In fact,
   almost all lightning has now ended within this cluster. However, a
   remnant MCV can still be seen in radar imagery from the KILX
   WSR-88D. 

   The 19Z RAOB from KILX shows the stable airmass with MLCIN near -200
   J/kg. However, the hodograph does show decent clockwise curvature
   within the lowest 3 km and moderate mid-level flow. This is likely a
   good proximity hodograph for later storms which are expected to form
   near this MCV later this afternoon/early evening. 

   Despite the lackluster storm development thus far, this is expected
   to change in the next 1 to 2 hours as this MCV moves into east
   central Illinois where the airmass was not worked over by overnight
   convection. In this region dewpoints are in the low 70s with
   temperatures in the mid 80s with the SPC mesoanalysis suggesting
   2000 J/kg MLCAPE. This instability, combined with 45 to 50 knots of
   effective shear per 19Z ILX RAOB and SPC mesoanalysis should be
   sufficient for supercell development. Any supercells which develop
   may have a risk of all hazards including a couple of tornadoes. The
   tornado threat will likely be greatest in a narrow corridor where
   winds are backed to southerly near the MCV and near the warm front
   where low-level vorticity should be enhanced.

   ..Bentley/Hart.. 06/20/2021

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...IWX...IND...LOT...ILX...

   LAT...LON   39828860 40048872 40738869 41348849 41618788 41638701
               41768622 41718552 41488527 40798527 40108660 40048723
               39728838 39828860
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