Jul 19, 2006 2000 UTC Day 1 Convective Outlook
Updated: Wed Jul 19 20:08:18 UTC 2006
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the upper mississippi valley and western great lakes this afternoon and evening....   Please read the latest public statement about this event.

Categorical Graphic
20060719 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20060719 2000 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20060719 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20060719 2000 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 192005
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0305 PM CDT WED JUL 19 2006
   
   VALID 192000Z - 201200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS FROM NRN/ERN IA INTO NRN/CENTRAL
   IL...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
   FROM THE UPPER MS VALLEY INTO THE UPPER GREAT LAKES...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER MS
   VALLEY/GULF COAST STATES...
   
   ...IA INTO NRN IL/NWRN INDIANA...
   ONGOING SEVERE MCS MOVING INTO NWRN IL IS EXPECTED TO CONTINUE
   MOVING SEWD INTO VERY WARM/MOIST ENVIRONMENT CHARACTERIZED BY
   SURFACE TEMPERATURES NEAR 90 AND DEW POINTS IN THE LOW/MID 70S. 
   THIS IS RESULTING IN MLCAPE OF 2500-4000 J/KG...AND WITH CONTINUED
   AFTERNOON HEATING FURTHER DESTABILIZATION IS LIKELY.  NWLY MID LEVEL
   WINDS OF 25-30 KT ACROSS THIS REGION IS CONTRIBUTING TO DEEP LAYER
   SHEAR OF 20-30 KT...WHICH IS SUFFICIENT TO MAINTAIN MESOSCALE
   ORGANIZATION OF THE CONVECTIVE SYSTEM. VERY LARGE HAIL AND DAMAGING
   WIND GUSTS WILL BE LIKELY AS THE STORMS MOVE SEWD 35 KT ACROSS PARTS
   OF NRN/CENTRAL IL THIS AFTERNOON.  THIS SYSTEM MAY CONTINUE SEWD
   INTO PARTS OF WEST CENTRAL/SWRN INDIANA THIS EVENING BEFORE SLOWLY
   WEAKENING AS IT MOVES INTO A REGION OF LESS FAVORABLE SHEAR.
   
   THE CURRENT MCS MOVING INTO NWRN IL HAS GENERATED A CONVECTIVE
   OUTFLOW BOUNDARY EXTENDING DIAGONALLY FROM SERN INTO NWRN IA AND
   EXTREME SERN SD...WHERE IT INTERSECTS A NE/SW ORIENTED COLD FRONT
   EXTENDING FROM NRN MN INTO CENTRAL NEB.  ALTHOUGH VISIBLE IMAGERY
   AND RUC FORECAST SOUNDINGS INDICATE THE LOW LEVEL AIR MASS IS
   CURRENTLY CAPPED OVER THIS REGION...PERSISTENT CONVERGENCE AND
   DYNAMIC FORCING ALONG THE SRN EDGE OF A SHORT WAVE TROUGH MOVING
   TOWARD THE UPPER MS VALLEY ARE EXPECTED TO WEAKEN THE CAP
   SUFFICIENTLY FOR NEW CONVECTION TO DEVELOP LATER THIS AFTERNOON AND
   EVENING.  VERY UNSTABLE CONDITIONS IMMEDIATELY SOUTH OF THE OUTFLOW
   BOUNDARY WITH MLCAPE EXCEEDING 4000 J/KG COUPLED WITH STRONG DEEP
   LAYER SHEAR/LOW LEVEL HELICITY INDICATE A FAVORABLE ENVIRONMENT FOR
   SUPERCELL THUNDERSTORMS CAPABLE OF PRODUCING VERY LARGE
   HAIL...DAMAGING WIND GUSTS...AND A FEW TORNADOES /PRIMARILY ALONG
   AND JUST NORTH OF THE OUTFLOW BOUNDARY/.  SEVERE CONVECTION IS
   FORECAST TO GROW UPSCALE INTO ANOTHER MCS LATER THIS EVENING AND
   TRACK ESEWD ALONG THE OUTFLOW BOUNDARY ACROSS THE MIDDLE MS
   VALLEY...WITH A CONTINUED THREAT FOR DAMAGING WIND GUSTS AND LARGE
   HAIL THROUGH THE OVERNIGHT HOURS.
   
   ...UPPER MS VALLEY INTO THE UPPER GREAT LAKES...
   ALTHOUGH THE CIRRUS CANOPY ASSOCIATED WITH THE IA/IL MCS EXTENDS NWD
   INTO SRN MN AND WI...LATEST VISIBLE IMAGERY SHOWS THINNING CLOUDS
   NEAR THE FRONT OVER EAST CENTRAL MN AND FAR NWRN WI.  THIS MAY
   PERMIT ENHANCED HEATING AND AIR MASS DESTABILIZATION TO
   OCCUR...INCREASING THE POTENTIAL FOR ADDITIONAL STRONG/SEVERE STORMS
   TO DEVELOP ALONG/AHEAD OF THE ADVANCING COLD FRONT.  A 50-60 KT MID
   LEVEL JET STREAK MOVING EWD ACROSS THIS AREA IN ASSOCIATION WITH THE
   SHORT WAVE TROUGH WILL INCREASE THE DYNAMIC FORCING FOR LARGE SCALE
   ASCENT AND CONTRIBUTE TO STRONG DEEP LAYER SHEAR.  ALTHOUGH THE
   ENVIRONMENT IS LESS UNSTABLE COMPARED TO REGIONS FARTHER
   SOUTH...THERE WILL CONTINUE TO BE A THREAT FOR SEVERE THUNDERSTORMS
   SPREADING EWD ACROSS THIS REGION LATER THIS AFTERNOON INTO TONIGHT.
   
   ...UPPER TN VALLEY INTO THE GULF COAST REGION...
   SCATTERED THUNDERSTORMS HAVE DEVELOPED FROM NRN AL SWD INTO PARTS OF
   SWRN GA/SRN AL AND CENTRAL/SRN MS.  THIS ACTIVITY IS WITHIN A 
   THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY AMPLE MOISTURE AND STEEP
   LAPSE RATES IN THE LOWEST 1-2 KM...WITH DRY AIR AND MODERATELY STEEP
   LAPSE RATES ALOFT.  20-25 KT NELY MID LEVEL WINDS WILL SUPPORT
   MODEST CONVECTIVE ORGANIZATION AND HELP MAINTAIN A THREAT FOR WET
   MICROBURSTS AND POSSIBLE HAIL WITH STRONGER CELLS.
   
   ...SRN APPALACHIANS NWD INTO PARTS OF VA...
   18Z GSO AND RNK RAOBS EXHIBIT VERY STEEP LOW LEVEL LAPSE RATES AND
   LARGE SURFACE TEMPERATURE/DEW POINT SPREADS...WHICH WILL ENHANCE
   DOWNDRAFT STRENGTH.  WEAK WINDS ALOFT AND MINIMAL VERTICAL SHEAR
   INDICATES LIKELIHOOD OF PULSE STORMS WITH ATTENDANT POTENTIAL FOR
   BRIEF MICROBURSTS.  THIS CONVECTION SHOULD WEAKEN AFTER SUNSET.
   
   ..WEISS.. 07/19/2006
   
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