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2021 Short/Medium Range Severe Thread


Hoosier
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5 hours ago, CheeselandSkies said:

What is it with May and June being dead in this region after 2016 (apart from 2019, which while the results weren't spectacular there were at least opportunities); with our regional chase "season" consisting of one day way closer to the cold season than seems right (2/28/17 and 12/1/18 being particularly egregious, also 3/28/20 which busted anyway compared to its ceiling) and one random day in the mid-late summer (7/19/18, 8/10/20)?

What I really need is a high-end event that can be predicted with 48 hour notice.  Driving south around both Lake Michigan AND Chicago traffic to reach rural Illinois in a single day is just impossible.  I tried on 6/22/2016 but just couldn't get to the action in time.  Don't know if there was even an actual tornado that day.

As for local stuff, 4/7/2020 was an interesting day here in terms of storm structure and lightning, but it was all after dark.  Most other times when there have been supercells around here, they were the HP blobs on an a slow moving W-E boundary... in like late August when the lake is warm.  Those are pretty cool for their crazy after-dark lightning shows, but not much else.  Actual tornados are mostly unpredictable land-spouts on days with visually uninspiring storm structures.  They do damage, but you can't really chase them at all.  Summer derecho season has been mostly dead since 2011.

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MO/IA/IL  
  
AN ARC OF CONVECTION, INCLUDING WIDELY SCATTERED THUNDERSTORMS,  
SHOULD DEVELOP AROUND MIDDAY IN A ZONE OF RELATIVELY MAXIMIZED  
DEEP-LAYER ASCENT, JUST NORTHEAST AND EAST OF THE STACKED LOW, AND  
ON THE EASTERN RIM OF ITS COLD-CORE REGION ALOFT.  THIS ACTIVITY --  
INITIALLY FROM WEST-CENTRAL/NORTHWESTERN MO ACROSS CENTRAL/EASTERN  
MO AND PERHAPS INTO WESTERN IL -- SHOULD MOVE GENERALLY NORTHWARD TO  
NORTHWESTWARD IN STEP WITH THE PREVAILING CYCLONIC-FLOW FIELD.  AT  
LEAST MARGINAL TORNADO AND WIND-DAMAGE POTENTIAL EXISTS THROUGH THE  
AFTERNOON, DECREASING THIS EVENING OVER IA AND NORTHWESTERN IL.  
  
LOW-LEVEL VORTICITY AND SRH WILL BE MAXIMIZED IN THE NOTCH OF  
SOUTHEASTERLY TO EAST-SOUTHEASTERLY SURFACE WINDS THAT WILL  
TRANSLATE NORTHWARD ACROSS THE OUTLOOK AREA, EAST-NORTHEAST OF AND  
IN STEP WITH THE LOW.  MIDLEVEL DCVA/COOLING WILL CONTRIBUTE TO  
STEEPENING LOW/MIDDLE-LEVEL LAPSE RATES AND AT LEAST WEAK BUOYANCY  
FOR SURFACE-BASED CONVECTION, EVEN WITH SURFACE DEW POINTS IN THE  
LOW/MID 50S AND TEMPERATURES NOT MUCH WARMER.  THE MAIN CONCERN/  
UNCERTAINTY AT THIS TIME IS THE AMOUNT OF BOUNDARY-LAYER  
DESTABILIZATION AVAILABLE TO THE CONVECTIVE ARC, AND IN TURN, THE  
MAGNITUDE AND WIDTH OF BUOYANCY TO SUPPORT ORGANIZED CONVECTIVE  
LONGEVITY.  BASELINE MLCAPE VALUES OF 300-700 J/KG ARE POSSIBLE IN A  
NARROW PLUME IMMEDIATELY PRECEDING THE ARC -- HIGHER WITH ANY  
SUSTAINED SLOTS OF SURFACE HEATING THAT CAN DEVELOP IN THE INFLOW  
REGION.  
  
MESOSCALE TRENDS WILL BE MONITORED CLOSELY, AND IF THEY BECOME MORE  
FAVORABLE, A SMALL CORRIDOR OF GREATER UNCONDITIONAL PROBABILITIES  
COULD BE ADDED WITHIN THE EXPANDED "MARGINAL" AREA IN A LATER  
UPDATE.  

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temps already 60ish in MO with dewpoints 50-53

nice clearing out

update

..MO/IA/IL  
  
LATEST SURFACE ANALYSIS SHOWS A DEEP LOW OVER EASTERN KS.  THIS LOW  
WILL TRACK NORTHEASTWARD TOWARD SOUTHWEST IA THIS AFTERNOON, WITH A  
WARM FRONT LIFTING NORTHWARD INTO SOUTHERN IA AND WESTERN IL.   
VISIBLE IMAGERY SHOWS CLEARING/HEATING OCCURRING OVER NORTHERN MO,  
WHERE TEMPERATURES IN THE 60S AND DEWPOINTS AROUND 50F WILL COMBINE  
WITH COLD MID-LEVEL TEMPERATURES TO YIELD MLCAPE VALUES OF 400-800  
J/KG.  FORECAST SHEAR PROFILES WILL SUPPORT LOW-TOPPED SUPERCELLS  
CAPABLE OF HAIL, GUSTY WINDS, AND A TORNADO OR TWO.  12Z CAM  
GUIDANCE VARIES ON CORRIDOR OF MAX POTENTIAL, AND LOW CAPE VALUES  
LIMIT THE CONFIDENCE OF A MORE ROBUST SEVERE THREAT.  NEVERTHELESS,  
AN UPGRADE TO SLGT IS POSSIBLE AT 20Z IF A MORE FOCUSED AREA OF  
CONCERN DEVELOPS.  
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ESOSCALE DISCUSSION 0239  
NWS STORM PREDICTION CENTER NORMAN OK  
1244 PM CDT TUE MAR 23 2021  
  
AREAS AFFECTED...NORTHERN MISSOURI...SOUTHERN IOWA...AND FAR WESTERN  
ILLINOIS  
  
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY   
  
VALID 231744Z - 231945Z  
  
PROBABILITY OF WATCH ISSUANCE...20 PERCENT  
  
SUMMARY...ISOLATED TO SCATTERED THUNDERSTORM DEVELOPMENT IS EXPECTED  
THROUGH THE AFTERNOON HOURS ACROSS NORTHERN MISSOURI AND INTO  
PORTIONS OF SOUTHERN IOWA AND FAR WESTERN ILLINOIS. DAMAGING WINDS  
AND HAIL WILL BE THE PRIMARY THREATS, THOUGH A TORNADO THREAT MAY  
EVOLVE LATER THIS AFTERNOON AND EVENING.  
  
DISCUSSION...VISIBLE SATELLITE TRENDS THROUGH THE LATE MORNING AND  
EARLY AFTERNOON HAVE SHOWN PARTIAL CLEARING WITHIN A MID-LEVEL DRY  
SLOT ON THE EASTERN PERIPHERY OF A STACKED SURFACE/UPPER-LEVEL LOW.  
THIS CLEARING HAS BEEN SUFFICIENT FOR TEMPERATURES TO WARM INTO THE  
LOW TO MID 60S AHEAD OF A SURFACE TROUGH/DRYLINE. DESPITE A MARGINAL  
INFLUX OF LOW-LEVEL MOISTURE (DEWPOINTS HAVE CLIMBED INTO THE  
LOW/MID 50S), RECENT RAP MESOANALYSIS SUGGESTS AROUND 500 J/KG  
MLCAPE IS IN PLACE ACROSS CENTRAL/NORTHERN MO. DEEPENING CUMULUS AND  
A FEW LIGHTNING STRIKES SUPPORT THIS IDEA AND INDICATE BUOYANCY IS  
SUFFICIENT TO SUPPORT AT LEAST TRANSIENT UPDRAFTS. INSTABILITY  
SHOULD INCREASE TO SOME DEGREE INTO THE LATE AFTERNOON AS  
TEMPERATURES CONTINUE TO WARM.   
  
RECENT ANALYSES ALSO REVEAL MARGINAL, BUT SUFFICIENT, EFFECTIVE BULK  
WIND SHEAR ORTHOGONAL TO THE SURFACE TROUGH TO SUPPORT DISCRETE,  
ORGANIZED CONVECTION. AS LOW-LEVEL LAPSE RATES CONTINUE TO STEEP VIA  
DIURNAL HEATING, A WIND AND HAIL THREAT SHOULD MATERIALIZE. GIVEN  
SOUTHEASTERLY SURFACE FLOW WITHIN THE NARROW WARM SECTOR (PER  
REGIONAL VWPS), A TORNADO OR TWO WILL BE POSSIBLE WITH THE MORE  
ROBUST STORMS. CONVECTION IS MOST LIKELY TO DEVELOP ACROSS NORTHERN  
MO INTO SOUTHERN IL THIS AFTERNOON. THERE IS SOME UNCERTAINTY  
REGARDING CONVECTIVE COVERAGE FURTHER EAST INTO IL. HOWEVER, THIS  
LOCATION MAY SEE THE HIGHEST TORNADO POTENTIAL LATER THIS AFTERNOON  
AND EVENING AS AN INCREASE IN THE LOW-LEVEL JET AUGMENTS EFFECTIVE  
SRH. A WATCH IS NOT ANTICIPATED AT THIS TIME, BUT CONDITIONS WILL  
CONTINUE TO BE MONITORED.  
  
..MOORE/HART.. 03/23/2021  
   

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The environment with this potential is really not that far off the environment from that day.

Guidance the past day or so have really slowed things, with most of the potential being across MO/S IA now.


.

Famous last words.

Today is as marginal as marginal gets.


.
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Models continue you to trend tomorrow’s system north. Not sure if separate thread is warranted. But latest models have significant sfc-1km srh values extending to i70 and Indiana is covered in UH tracks

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This second system will have way more juice to work with... and the GFS has finally fallen in line with a stronger system.  These deepening systems with moisture are always dangerous this time of year.  :unsure:  Would prefer if it was February and this was a snowstorm as the track is perfect for MBY.

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URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 51
   NWS Storm Prediction Center Norman OK
   345 PM CDT Thu Mar 25 2021

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Southern Illinois
     Southern Indiana
     Western and Central Kentucky
     Southeast Missouri
     Northeast Mississippi
     Western and Middle Tennessee

   * Effective this Thursday afternoon and evening from 345 PM until
     1100 PM CDT.

   * Primary threats include...
     A few tornadoes and a couple intense tornadoes likely
     Scattered damaging winds and isolated significant gusts to 75
       mph likely
     Scattered large hail likely with isolated very large hail events
       to 2 inches in diameter possible

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