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Tim from Springfield (IL)

May 13-19 Severe/Heavy Rain threats

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National Weather Service Chicago/Romeoville, IL
302 PM CDT Thu May 14 2020

.SHORT TERM...
249 PM CDT

Through Friday...

Lingering showers and thunderstorms have diminished in coverage and
exited to the east of the area this afternoon. Meanwhile, dew points
have surged into the low to mid 60s across the area. The extensive
cloud cover has limited surface warming somewhat, but current
satellite trends suggest the cirrus beginning to thin which should
help temperatures warm up into the low 70s across much of the area.

An east-west oriented boundary has set up across southern Iowa
into northern IL, combined with strengthening low level jet will
set the stage for potential severe weather and heavy rain this
evening and overnight.

The primary corridor for severe weather has shifted south mainly
along and south of I-80 where the better instability will be.
Conditions are not as favorable as once thought thanks to the
continued precip through the morning and early afternoon hours which
has prevented the surface boundary from lifting as far north. In
general, expecting things to begin in multi-cell clusters this
evening and transition to a more linear mode and track off to the
east. Primary severe weather threats will be strong winds on the
leading edge of this line. Some hail may be possible with the
stronger storms, especially at the onset and a QLCS tornado threat
cannot be entirely ruled out.

Of greater concern with this system is the potential for training
thunderstorms resulting in flash flooding. The upwind Corfidi
vectors for propagation into the inflow are light and even
oriented to the northeast which suggests that redevelopment
behind the leading edge of the line is possible resulting in heavy
rain falling over the same areas for multiple hours. Current
thinking and trends is that this will favor along and near the
I-80 corridor. Have fielded a Flash Flood Watch to account for the
potential for heavy rain. Wherever this ultimately sets up could
see locally heavy rain amounts of 3-4+ inches of rain when this is
all said and done. If the cold pool ends up being stronger it may
be able to help push this out of the area more quickly reducing
the flooding potential, but current thinking is this will be
limited in its influence.

Once overnight showers and thunderstorms move out Friday morning a
mostly quiet day between systems. Temperatures are expected in the
70s, (60s closest to the lake). A lake breeze is expected to develop
in the afternoon which will lead to quick cooling behind it.

Aside from the severe weather and flooding threat, dense marine fog
is expected across southern Lake Michigan through late morning
tomorrow.

Petr

&&

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this pattern reminds me so much of something more mid summer-like (besides the temps), explosive convective growth in Iowa, modest mid and upper level winds and training thunderstorms later over Illinois.

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There's a tornado warning near Chariton, IA, which is south of Des Moines. It's a pretty well-formed hook echo right now.

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12 minutes ago, Chinook said:

There's a tornado warning near Chariton, IA, which is south of Des Moines. It's a pretty well-formed hook echo right now.

Pretty good bounded weak echo region now.

3B0F4698-44C9-4216-9164-A467B80274DC.png

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Graphic for MPD #0190

Mesoscale Precipitation Discussion 0190
NWS Weather Prediction Center College Park MD
522 PM EDT Thu May 14 2020

Areas affected...Southern IA...far northern MO

Concerning...Heavy rainfall...Flash flooding possible

Valid 142120Z - 150200Z

SUMMARY...Storms training over areas that received heavy rainfall
earlier today could pose a flash flood threat through late this
afternoon into early this evening.

DISCUSSION...The GOES-16 visible loop showed a line of towering
cumulus forming along and just north of a stationary boundary
across portions of southern IA. The formation zone lies on the
northern edge of the instability gradient, with SBCAPE over 3000
J/KG over northernmost MO into far southern IA.

The storms are developing on the northern edge of the better
moisture source, and the combination of moisture and instability
allowed storms over Atlantic and Guthrie Center counties to
produce hourly rainfall rates in excess of 2.25 inches (though the
DMX HCA product does indicate the potential for hail
contamination) within the last 90 minutes.

The 850/300 mb mean wind is generally aligned with the propagation
vectors across southern and central IA, which could foster an
environment conducive to continued training. However, without a
clear source of lift over the boundary, it is not clear just how
extensive the convection becomes along and south of the boundary
through 15/00z. Both the latest HRRR/parallel HRRR solutions do
have a handle on the initial convective placement, but do not
necessarily have a handle on the intensity of the rainfall with
the storms themselves.

Each model shows a general increase in coverage as higher
instability is slowly advected along the front into southern IA.
The best coverage (based on the simulated radar imagery from the
HRRR/parallel HRRR is expected across southwest IA, where an area
of 1.00/2.00 inches of rainfall occurred in earlier convection.
Storms training over this area could produce an additional
1.00/2.00 inches or train, which pose a flash flood threat through
late afternoon and early evening.

Since the coverage of storms in the area that received heavy
rainfall earlier today is still unclear, flash flooding is
considered possible.

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7 hours ago, Chicago Storm said:

While there is a still a SLGT worthy severe risk for the area (even if SPC did trim it, they have been meh), the flood threat looks to steal the show overall.

Upwards of 1.00-2.50" of rain fell across a corridor within N Illinois last night/this morning. It looks like a good portion of that corridor will overlap with the heaviest for this afternoon/tonight, with upwards of another 2-5" of rain possible. Could be seeing final totals in that overlap region in excess of 6"...if things line up correctly.

Can probably toss this now for the most part.

Looks like any training with excessive totals will now be more isolated/localized...instead of more widespread as it looked earlier.

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6 minutes ago, Chicago Storm said:

Can probably toss this now for the most part.

Looks like any training with excessive totals will now be more isolated/localized...instead of more widespread as it looked earlier.

I dunno.  Pretty stout cluster in Iowa and development near PIA.  Could be enough stability.  

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BULLETIN - EAS ACTIVATION REQUESTED  
TORNADO WARNING  
NATIONAL WEATHER SERVICE LINCOLN IL  
754 PM CDT THU MAY 14 2020  
  
THE NATIONAL WEATHER SERVICE IN LINCOLN HAS ISSUED A  
  
* TORNADO WARNING FOR...  
  SOUTHEASTERN MARSHALL COUNTY IN CENTRAL ILLINOIS...  
  NORTHERN WOODFORD COUNTY IN CENTRAL ILLINOIS...  
  
* UNTIL 845 PM CDT.  
      
* AT 754 PM CDT, A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO  
  WAS LOCATED NEAR WASHBURN, OR 8 MILES SOUTH OF LACON, MOVING  
  NORTHEAST AT 30 MPH.  
  
  HAZARD...TORNADO.  
  
  SOURCE...RADAR INDICATED ROTATION.  
  
  IMPACT...FLYING DEBRIS WILL BE DANGEROUS TO THOSE CAUGHT WITHOUT   
           SHELTER. MOBILE HOMES WILL BE DAMAGED OR DESTROYED.   
           DAMAGE TO ROOFS, WINDOWS, AND VEHICLES WILL OCCUR.  TREE   
           DAMAGE IS LIKELY.  
  
* THIS DANGEROUS STORM WILL BE NEAR...  
  WASHBURN AROUND 805 PM CDT.  
  VARNA AROUND 820 PM CDT.  
  TOLUCA AROUND 825 PM CDT.  
  WENONA AROUND 835 PM CDT.  

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That tornado warned cell is on the far western edge of 200 m2 and higher helicity to the east in In and east of much higher helicity in se IA.

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9 minutes ago, Indystorm said:

That tornado warned cell is on the far western edge of 200 m2 and higher helicity to the east in In and east of much higher helicity in se IA.

Main issue is no surface flow.

Probably would have produced otherwise.

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2 minutes ago, Chicago Storm said:

Main issue is no surface flow.

Probably would have produced otherwise.

Ya.  I do think Chi town environs will be in for a bumpy night with those storms moving ne and storms coming in from the west.  Probably a very good lightning show.

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9 minutes ago, Indystorm said:

Ya.  I do think Chi town environs will be in for a bumpy night with those storms moving ne and storms coming in from the west.  Probably a very good lightning show.

Quite a bit of lightning to my south. 

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1 hour ago, Chicago Storm said:

Can probably toss this now for the most part.

Looks like any training with excessive totals will now be more isolated/localized...instead of more widespread as it looked earlier.

Might have said this too soon...We'll see.

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I chased the supercell that went over Washburn, IL earlier. I ended up getting right under the main rotation and there was some wicked motion. I can't wait to look through my footage on this one!

20200514_194233(0).thumb.jpg.204acdc843fa9c9596e79ee46aebfd99.jpg

 

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BULLETIN - EAS ACTIVATION REQUESTED  
TORNADO WARNING  
NATIONAL WEATHER SERVICE QUAD CITIES IA/IL  
1020 PM CDT THU MAY 14 2020  
  
THE NATIONAL WEATHER SERVICE IN THE QUAD CITIES HAS ISSUED A  
  
* TORNADO WARNING FOR...  
  EAST CENTRAL HENRY COUNTY IN NORTHWESTERN ILLINOIS...  
  
* UNTIL 1045 PM CDT.  
      
* AT 1020 PM CDT, A TORNADO PRODUCING STORM WAS LOCATED NEAR  
  ATKINSON, OR 8 MILES NORTHWEST OF KEWANEE, MOVING NORTHEAST AT 50  
  MPH.  
  
  HAZARD...DAMAGING TORNADO.  
  
  SOURCE...RADAR CONFIRMED TORNADO.  
  
  IMPACT...FLYING DEBRIS WILL BE DANGEROUS TO THOSE CAUGHT WITHOUT   
           SHELTER. MOBILE HOMES WILL BE DAMAGED OR DESTROYED.   
           DAMAGE TO ROOFS, WINDOWS, AND VEHICLES WILL OCCUR.  TREE   
           DAMAGE IS LIKELY.  
  
* THIS TORNADIC STORM WILL BE NEAR...  
  ANNAWAN AROUND 1030 PM CDT.  
  
OTHER LOCATIONS IMPACTED BY THIS TORNADIC THUNDERSTORM INCLUDE GERMAN  
CORNER AND JOHNSON-SAUK TRAIL STATE PARK.  

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Came back earlier from a walk. Just in time I thought as the light show just south from here in Joilet was sparking and creeping up.  

@RyanDe680 are you seeing it? Going to be nice tonight. Activity creeping and knocking on the door now

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There has been a significant meso with the storm moving across Lee Co, with associated WAA wing extending eastward into the Chicago metro.

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1 minute ago, Chicago Storm said:

There has been a significant meso with the storm moving across Lee Co, with associated WAA wing extending eastward into the Chicago metro.

Storm needs a tor warning.

Two couplets in Lee Co currently, and becoming better defined with closer approach to radar.

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