May 20-21 Severe Threat

[IWXwx]

I figured I'd start a thread for this threat even though the chance for spinups are slim. Might be quite a few wind and hail reports.

 

As Stebo said in the Medium Range thread, if we can get any sups this afternoon, ping pong balls or better may be possible. Downstream in my area, I'm looking forward to a nocturnal MCS. Not fun from a spotter perspective, but cool to observe.

 

Wednesday looks to be more of a southern IL, IN, and OH threat. I've got a hunch that Fort Wayne/Detroit might be out of play for severe tomorrow even though SPC has us in a slight, but we'll see.

[A-L-E-K]

30% hatched for hail right across the heart of the metro

 

looks like we'll see plenty of sun

 

looking forward to the evening

[A-L-E-K]

   THERE ARE A VARIETY OF FORECAST SCENARIOS ACROSS THE MIDWEST SLGT
   RISK AREA TODAY AND TONIGHT. THAT VARIETY INTRODUCES UNCERTAINTY AS
   TO TIMING OF CONVECTIVE INITIATION...STORM MODE...AND POSSIBLE
   MCS/QLCS EVOLUTION. THE MOST LIKELY SCENARIO GIVEN AN ABUNDANCE OF
   GUIDANCE...THE PATTERN AND TIME OF YEAR...IS THAT ROBUST CONVECTION
   WILL INITIATE AHEAD OF THE COLD FRONT FROM ERN IA TO SRN WI IN THE
   21Z TO 00Z TIME FRAME. BULK SHEAR IN THE 40-50KT RANGE...AND
   AFOREMENTIONED INSTABILITY PARAMETERS...WILL BE MORE THAN ADEQUATE
   FOR SUPERCELLS WITH THE POTENTIAL TO PRODUCE VERY LARGE HAIL AND
   STRONG WINDS. A TORNADO THREAT WILL ALSO EXIST DURING THIS INITIAL
   PHASE...ESPECIALLY NEAR WEAK FRONTAL WAVES AND/OR STORM-SCALE/
   MESOSCALE BOUNDARIES. THE COMBINATION OF STRENGTHENING UPPER FORCING
   AND LINEAR CONVERGENCE ON THE ADVANCING FRONT SHOULD CONTRIBUTE TO
   AN EVENING TRANSITION TO A FORWARD PROPAGATING QLCS. THIS TRANSITION
   SHOULD OCCUR AMIDST MODERATE INSTABILITY...AND ON THE SRN EDGE OF
   50-60KT MID-LEVEL WLY FLOW. THE EVOLVING QLCS COULD PRODUCE NUMEROUS
   DAMAGING WIND EVENTS FROM THE CHICAGO AREA SOUTH AND EAST ACROSS
   LAKE MICHIGAN TO NRN IND/SWRN LWR MI THROUGH LATE EVENING. ISOLATED
   SIGNIFICANT WIND GUSTS ARE POSSIBLE IF QLCS UPSCALE GROWTH IS
   REALIZED RELATIVELY EARLY IN THE EVENING WHEN SFC-BASED INSTABILITY
   WILL BE GREATER. HOWEVER...CERTAINTY IN THIS SCENARIO IS NOT
   SUFFICIENT ENOUGH AT THIS TIME TO WARRANT HIGHER SIGNIFICANT WIND
   PROBABILITIES AND/OR THE INTRODUCTION OF A MDT RISK FOR SOME OF THE
   AREA.
 

 

[geddyweather]

1230z outlook going even higher. 5% tornado and 30% hatched hail over nrn IL and IN. 30% wind risk extended eastward towards Cleveland... Not quite sure I'm convinced, though.  Lots of cloud cover around (at least where I'm located), though its obviously early in the game right now. 

 

[A-L-E-K]

1230z outlook going even higher. 5% tornado and 30% hatched hail over nrn IL and IN. 30% wind risk extended eastward towards Cleveland... Not quite sure I'm convinced, though.  Lots of cloud cover around (at least where I'm located).

 

 

 

 

 

at least glance at visible before complaining about cloud cover

 

http://www.ssec.wisc.edu/data/wisc/

[Thundersnow12]

I'll be out chasing for sure. Don't know about the tornado threat but do like the supercell and big hail threat.

[geddyweather]

at least glance at visible before complaining about cloud cover

 

http://www.ssec.wisc.edu/data/wisc/

 

Wasn't complaining, but I got your point.

[AppsRunner]

SPC looks like they want to upgrade to a moderate risk but are playing the waiting game for now. Definitely more interesting for the Chicago area but more of a night time light show here. 

[A-L-E-K]

I'll be out chasing for sure. Don't know about the tornado threat but do like the supercell and big hail threat.

 

 

hail chasing ftl

[Stebo]

hail chasing ftl

If your car is <$1000 dollars I call it a wash

 

I do see SPC shifted the risks on the 1230Z outlook, I agree much more with these risk orientations compared to the initial ones. Interesting to note, both the HRRR and the 4km NAM keep the convection more in clusters of supercells after initial formation vs blowing it up into a huge MCS.

[A-L-E-K]

can't wait to check out some dusk mammatus over the lake

[SchaumburgStormer]

Full sun in RFD, 75/61. Looking forward to some nice looking storms a bit later.

[Thundersnow12]

Really a battle right now between the NAM/GFS vs more hi res guidance 4km NAM/HRRR about timing of initiation. I like a compromise right now

[OceanStWx]

Modifying the 12z DVN sounding for their forecast high of about 82 yields CAPE between 2000-2500 J/kg nearly uncapped.

[A-L-E-K]

Really a battle right now between the NAM/GFS vs more hi res guidance 4km NAM/HRRR about timing of initiation. I like a compromise right now

 

 

12z NMM pretty far south with initiation

 

[hm8]

New outlook shrinks risk zone, removes hail hatching...

[A-L-E-K]

81/63 at MDW

[Thundersnow12]

81/63 at MDW

 

Most places will blow by their fcst high. 

 

Already 80 at DVN. 

 

HRRR/RAP yet again will be closer on the highs it looks like. 

[OceanStWx]

Most places will blow by their fcst high. 

 

Already 80 at DVN. 

 

HRRR/RAP yet again will be closer on the highs it looks like. 

 

Mid 80s over low 60s is going to be a lot closer to the 2500 J/kg number.

[Thundersnow12]

Mid 80s over low 60s is going to be a lot closer to the 2500 J/kg number.

 

And with plenty of shear overall shear  and discrete mode for awhile. Never know.. 

[snowlover2]

New day 2

 

 

 

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1226 PM CDT TUE MAY 20 2014

VALID 211200Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS FOR THE CNTRL HIGH PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS FOR THE OH VALLEY TO LOWER
MID-ATLANTIC...

...SUMMARY...
ISOLATED TO SCATTERED SEVERE STORMS PRODUCING LARGE HAIL SHOULD
DEVELOP ALONG PARTS OF THE CENTRAL HIGH PLAINS WEDNESDAY AFTERNOON.
ISOLATED TO SCATTERED SEVERE STORMS WITH HAIL AND DAMAGING WIND
SHOULD OCCUR FROM THE OHIO VALLEY TO LOWER MID-ATLANTIC.

...SYNOPSIS...
A CUTOFF MID-LEVEL CYCLONE WILL PERSIST OVER THE SOUTHWEST WHILE AN
ANTICYCLONE REMAINS ANCHORED OVER THE LOWER MS VALLEY. A RIDGE
EMANATING NWWD TOWARDS THE HIGH PLAINS WILL BUILD SLIGHTLY AS THE
CYCLONE SHIFTS SLOWLY SWD AND FILLS. A SHORTWAVE TROUGH CENTERED
OVER NRN ONTARIO TO LK SUPERIOR SHOULD GRADUALLY SLIDE SEWD ACROSS
THE GREAT LAKES INTO EARLY THU. ATTENDANT SURFACE CYCLONE WILL
FOLLOW A SIMILAR TRACK...WITH A COLD FRONT CROSSING THE MIDWEST AND
TRAILING PORTION REMAINING QUASI-STATIONARY OVER KS.

.

...OH VALLEY TO LOWER MID-ATLANTIC...
WITH GPS PW VALUES OF 1-1.25 INCH CURRENTLY CONFINED TO PORTIONS OF
THE MIDWEST/GREAT LAKES AND SOUTHEAST...CONFIDENCE REMAINS LOW IN
THE DEGREE OF MOISTENING DEPICTED IN GUIDANCE. EVEN THOUGH GUIDANCE
IS LIKELY TOO MOIST WITH BOUNDARY LAYER DEW POINTS...SUFFICIENT
LOW-LEVEL MOISTURE SHOULD EXIST FOR AT LEAST WEAK TO MODERATE
BUOYANCY WHERE ROBUST DIURNAL HEATING OCCURS OUTSIDE OF LINGERING D1
CONVECTION. THIS HEATING SHOULD HELP REINVIGORATE CONVECTION ACROSS
AND E OF THE CNTRL APPALACHIANS. ALTHOUGH THIS REGION WILL LIKELY
REMAIN E OF STEEPER MID-LEVEL LAPSE RATES...30-40 KT EFFECTIVE SHEAR
WOULD SUPPORT A RISK FOR ISOLATED HAIL AND DAMAGING WINDS.

UPSTREAM ACROSS THE OH VALLEY...MODEST LOW-LEVEL CONVERGENCE ALONG
THE FRONT AND ANY LINGERING CONVECTIVE OUTFLOWS SHOULD AID IN
ISOLATED TO WIDELY SCATTERED STORMS BY LATE AFTERNOON ALONG THE EDGE
OF GREATER MLCIN OVER THE CNTRL STATES. AMIDST MODERATE TO STRONG
MID-LEVEL W/NWLYS AND ON THE PERIPHERY OF AN EXPANSIVE EML PLUME...A
MIX OF SUPERCELLS AND ORGANIZED LINE SEGMENTS COULD DEVELOP WITH
PRIMARY RISKS OF LARGE HAIL AND DAMAGING WINDS.

 

[hm8]

Hi res stuff (including HWT stuff)

 

 

 

 

 

 

[hm8]

Looks like the majority of hi res models take the bow echo south of SEMI

[IWXwx]

I figured I'd start a thread for this threat even though the chance for spinups are slim. Might be quite a few wind and hail reports.

 

As Stebo said in the Medium Range thread, if we can get any sups this afternoon, ping pong balls or better may be possible. Downstream in my area, I'm looking forward to a nocturnal MCS. Not fun from a spotter perspective, but cool to observe.

 

Wednesday looks to be more of a southern IL, IN, and OH threat. I've got a hunch that Fort Wayne/Detroit might be out of play for severe tomorrow even though SPC has us in a slight, but we'll see.

 

New Day 2 did take Detroit out and FWA is on the edge. Looking like Cincinnati is in for some fun tomorrow.

 

If I wasn't tied to spotting for my county, I'd chase some hailers, as I already have scars on my truck from running through previous hail cores. And as Thundersnow says, you never know with those early discrete cells.

[A-L-E-K]

these early evening complexes that fire over N. IL and move over the lake into MI/IN around dust always produce the best skies

[Eric In NW Ohio]

Those bow echo's (even as a forecast) freak me out. We were in the direct path of the Derecheo here in northwest Ohio a few summers back...that event was something I'll not soon forget, but, really do not want to re-live either!

 

Eric

[Thundersnow12]

Best storm might end up being in western IA early on. 

 

HRRR continues to blow up a sup in that area. 

[A-L-E-K]

83/64

[Thundersnow12]

AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL  
112 PM CDT TUE MAY 20 2014  
   
MESOSCALE DISCUSSION  
 
110 PM CDT  
 
THE MAIN FOCUS THIS AFTERNOON WILL BE TIMING THE INITIATION OF  
CONVECTION LATER THIS AFTERNOON AND EVENING ACROSS THE AREA.  
 
STRONG TO SEVERE THUNDERSTORMS STILL APPEAR TO BE IN THE WORKS FOR  
PORTIONS OF THE AREA LATER TODAY AND ESPECIALLY THIS EVENING WITHIN  
THE VICINITY OF SLOW MOVING COOL FRONTAL BOUNDARY. THIS COOL FRONTAL  
BOUNDARY IS CURRENTLY LOCATED FROM NORTHEASTERN IOWA...WEST  
SOUTHWESTWARD ACROSS KANSAS. THE AIRMASS AHEAD OF THIS BOUNDARY  
FEATURES DEWPOINTS MAINLY IN THE LOWER 60S...WITH TEMPERATURES  
NEARING 80 DEGREES AS OF THE NOON HOUR UNDER SUNNY SKIES.  
 
WATER VAPOR IMAGERY THIS MORNING INDICATES THE PRESENCE OF A  
BROAD MID LEVEL RIDGE ACROSS THE CENTRAL STATES WEDGED BETWEEN  
TWO UPPER LOWS/TROUGHS OVER EAST COAST. THIS IS DRIVING THE MAIN  
BELT OF MID/UPPER WESTERLIES RIGHT ACROSS THE UPPER MIDWEST AND  
GREAT LAKES REGION. THE MORNING RAOBS INDICATED THAT NORTHERN  
ILLINOIS WAS ALONG THE SOUTHERN PERIPHERY OF THIS STRONGER MID/UPPER  
LEVEL FLOW. SEVERAL SMALL SCALE DISTURBANCES...CURRENTLY NOTED IN  
THE WATER VAPOR IMAGERY ACROSS NEBRASKA AND INTO WESTERN IOWA...WILL  
BE OF INTEREST LATER THIS AFTERNOON AS THEY SHIFT EASTWARD TOWARDS  
THE INCREASINGLY UNSTABLE ENVIRONMENT DEVELOPING ACROSS THE AREA.  
 
IT APPEARS THAT STORMS MAY BEGIN TO INITIATE OVER THE NEXT FEW HOURS  
ACROSS PORTIONS OF SOUTHERN IOWA...WHERE BETTER LOWER LEVEL  
CONVERGENCE IS OCCURRING ALONG THE BOUNDARY. THIS ACTIVITY WOULD  
LIKELY SHIFT/DEVELOP EASTWARD ACROSS NORTHERN ILLINOIS BY EARLY THIS  
EVENING. ADDITIONAL STORMS MAY ALSO DEVELOP ACROSS SOUTHEASTERN  
WI...WHERE THE LATEST VIS SAT IMAGERY INDICATES SOME CU FIRING ALONG  
A LAKE BREEZE BOUNDARY. THE RAP SUGGESTS THAT STORM DEVELOPMENT  
HERE COULD DRIVE A BOUNDARY SOUTH ACROSS NORTHEASTERN ILLINOIS...IN  
WHICH STORMS WOULD DEVELOP. EITHER WAY...MUCH OF THE HIRES GUIDANCE  
SUGGESTS THAT THUNDERSTORM ACTIVITY WILL BEGIN TO IMPACT NORTHERN  
ILLINOIS BY THIS EVENING..LIKELY AFTER 5 PM. THE PRESENCE OF VERY  
STEEP MID LEVEL LAPSE RATES...7+C/KM...PER 12 UTC RAOBS...ALONG WITH  
THE POTENTIAL OF SUPERCELLS GIVEN THE DEEP LAYER  
SHEAR...CERTAINLY SUGGESTS THAT VERY LARGE HAIL WILL BE A THREAT  
WITH THESE STORMS TONIGHT. THERE IS ALSO THE THREAT OF STRONG  
DAMAGING WINDS THIS EVENING...ESPECIALLY IF THE CONVECTIVE  
ACTIVITY CONGEALS INTO A FORWARD PROPAGATING MCS.  
 
ALTHOUGH THE ATMOSPHERE IS NOT OVERLY MOIST...PRECIPITABLE WATER  
VALUES ARE PROGGED TO APPROACH 1.5 INCHES BY THIS EVENING.  
IN ADDITION...THE DEEP LAYER WIND FIELDS SUGGEST THAT STORM  
MOTIONS WILL BE MAINLY FROM WEST TO EAST...WHICH COULD RESULT IN SOME  
TRAINING OF CELLS OVER THE SAME AREAS ACROSS NORTHERN ILLINOIS INTO  
THIS EVENING. THIS RAISES SOME CONCERNS FOR SOME HEAVY RAINFALL  
POTENTIAL IN ADDITION TO THE SEVERE THREAT THIS EVENING. AS A RESULT  
OF THIS...THERE IS APPEARS TO BE A CONDITIONAL THREAT FOR SOME  
ISOLATED AREAS EXCEEDING FLASH FLOOD GUIDANCE.  
 
KJB  

[Stebo]

I would watch central and western Michigan for potential convective initiation anything that forms there would ride the warm front toward southeast MI.