Jun 12, 2013 2000 UTC Day 1 Convective Outlook
Updated: Wed Jun 12 20:04:37 UTC 2013
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over portions of the middle mississippi valley east to the upper ohio valley and lower great lakes this afternoon and tonight....   Please read the latest public statement about this event.  View What is a Watch? clip.

Categorical Graphic
20130612 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20130612 2000 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20130612 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20130612 2000 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
HIGH 32,586 11,932,486 Chicago, IL...Ft. Wayne, IN...Aurora, IL...Rockford, IL...Joliet, IL...
MODERATE 68,983 12,667,822 Indianapolis, IN...Columbus, OH...Cincinnati, OH...Toledo, OH...Dayton, OH...
SLIGHT 422,975 53,149,315 Charlotte, NC...Detroit, MI...Baltimore, MD...Washington, DC...Louisville, KY...
   SPC AC 122000

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0300 PM CDT WED JUN 12 2013

   VALID 122000Z - 131200Z

   ...THERE IS A HIGH RISK OF SVR TSTMS FROM EXTREME ERN IA...NRN
   IL...NRN IND...EXTREME SWRN MI AND EXTREME NWRN OH...

   ...THERE IS A MDT RISK OF SVR TSTMS FROM ERN IA...CNTRL AND NRN
   IL...SRN WI...SWRN MI...IND...AND WRN OH...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY INTO
   THE OH VALLEY...SRN GREAT LAKES AND MID ATLANTIC REGION...

   ...THERE IS A SLGT RISK OF SVR TSTMS CNTRL AND ERN MT INTO NERN
   WY...

   ...UPPER MS VALLEY SRN GREAT LAKES AND OH VALLEY REGION...

   ONLY MINOR CHANGES HAVE BEEN MADE TO ONGOING FORECAST. THREAT FOR A
   SIGNIFICANT WIDESPREAD DAMAGING WIND EVENT STILL APPEARS ON TRACK
   FROM SRN PORTIONS OF THE GREAT LAKES INTO THE OH VALLEY REGION HIGH
   AND MODERATE RISK AREAS.

   STORMS ARE IN PROCESS OF DEVELOPING FROM NERN IA INTO SRN WI WITHIN
   ZONE OF DPVA AND ASCENT ACCOMPANYING A PROGRESSIVE SHORTWAVE TROUGH
   GENERALLY NE OF SFC LOW AND NORTH OF E-W QUASI-STATIONARY FRONT. THE
   INITIAL SFC BASED STORMS DEVELOPING EAST OF SFC LOW MAY ORGANIZE AS
   DISCRETE SUPERCELLS WITH AN INITIAL TORNADO THREAT. STORMS SHOULD
   EVENTUALLY CONSOLIDATE AND TRANSITION TO A FORWARD PROPAGATING MCS
   WITH AN INCREASING THREAT FOR SIGNIFICANT WIND DAMAGE AS IT MOVES
   ESEWD THROUGH THE SRN GREAT LAKES AND OH VALLEY DURING THE EVENING
   AND OVERNIGHT.

   ...MT AND NERN WY...

   REF SWOMCD 1042.

   ..DIAL.. 06/12/2013

   .PREV DISCUSSION... /ISSUED 1126 AM CDT WED JUN 12 2013/

   ...SYNOPSIS...
   A SIGNIFICANT SEVERE WEATHER OUTBREAK APPEARS INCREASINGLY LIKELY
   ACROSS PORTIONS OF THE UPPER MIDWEST/LOWER GREAT LAKES FROM THIS
   AFTERNOON THROUGH THIS EVENING. INTENSE STORM DEVELOPMENT IN A VERY
   UNSTABLE AIRMASS...COINCIDENT WITH A COMPACT AND INTENSIFYING
   SURFACE LOW SHOULD RESULT IN NUMEROUS DAMAGING WIND EVENTS AS WELL
   AS SCATTERED...POSSIBLY STRONG TORNADOES.

   ...ERN IA/NRN IL/NRN IND/NWRN OH AND ADJACENT AREAS OF EXTREME SRN
   WI AND SWRN LOWER MI...

   SIGNIFICANT SEVERE WEATHER INGREDIENTS HAVE CONGEALED AHEAD OF A
   COMPACT AND PROGRESSIVE MID/UPPER TROUGH AND ASSOCIATED 50-60KT MID
   LEVEL WLY FLOW CURRENTLY TRACKING EAST FROM THE NRN/CNTRL PLAINS. AN
   EXPANSIVE WARM/MOIST SECTOR EXISTS AHEAD OF THE UPPER FORCING AND
   DEVELOPING SURFACE CYCLONE WITH 2M DEWPOINTS WELL INTO THE 60S AND
   LOWER 70S F AND PW VALUES IN EXCESS OF 1.25 INCHES ACROSS MUCH OF
   THE MIDWEST FROM IA EAST ACROSS IL/IND/OH. MORNING SOUNDINGS ACROSS
   THIS SAME REGION INDICATE A PRONOUNCED EML ADVECTING EAST FROM THE
   SRN HIGH PLAINS WITH 700-500MB LAPSE RATES APPROACHING 9C/KM.

   DESPITE RELATIVELY STRONG CAPPING ACROSS THE WARM SECTOR...DEGREE OF
   HEATING AND LARGE SCALE ASCENT AIDING SURFACE CYCLONE
   INTENSIFICATION ACROSS ERN IA BY LATE AFTERNOON WILL PROVE ADEQUATE
   FOR SURFACE-BASED STORM INITIATION. ADDITIONAL NEAR-SURFACE-BASED
   DEEP CONVECTION WITH BOTH HAIL AND WIND POTENTIAL MAY PRECEDE TRULY
   SURFACE-BASED STORMS TO THE NORTH OF THE SURFACE LOW AND
   QUASI-STATIONARY FRONT SITUATED FROM NERN IA ACROSS SRN WI TO LOWER
   MI. GIVEN DEGREE OF CAPPING AND MAGNITUDE OF INSTABILITY...EXPECT
   POTENTIALLY EXPLOSIVE STORM DEVELOPMENT TO OCCUR IN THE PRESENCE OF
   MODEST TO LOCALLY STRONG STORM-RELATIVELY HELICITY /SRH/. ANY
   CONVECTION INITIATING NEAR THE SURFACE LOW AND FRONT WILL QUICKLY
   ACQUIRE SUPERCELL CHARACTERISTICS GIVEN DEGREE OF EFFECTIVE VERTICAL
   SHEAR OF 35-55KT. POTENTIALLY STRONG TORNADO THREAT MAY BE MAXIMIZED
   DURING THIS EARLY DEVELOPMENT PHASE /21Z-00Z/ NEAR THE LOW AND FRONT
   WHILE STORMS REMAIN DISCRETE AMIDST HIGH INSTABILITY AND EFFECTIVE
   SRH IN EXCESS OF 200 M2/S2.

   ORGANIZING INFLUENCE OF THE DEEPENING SURFACE CYCLONE RIPPLING EAST
   ALONG THE WARM/QUASI-STATIONARY FRONT...IN CONCERT WITH 50-60KT
   MID-LEVEL JET STREAK DIRECTED PREFERENTIALLY INTO/ACROSS THE
   DEVELOPING MASS OF CONVECTION SUGGESTS UPSCALE PROGRESSIVE MCS
   /POSSIBLE DERECHO/ EVOLUTION THROUGH THE EVENING HOURS. GIVEN
   ANTECEDENT AIRMASS CHARACTERISTICS...STRENGTH OF LARGE SCALE
   FORCING...AND DEPICTION OF CURRENT CONDITIONS...RELATIVELY HIGH
   CONFIDENCE EXISTS IN A NUMBER OF STORM-SCALE MODEL SIMULATIONS
   SHOWING MCS/DERECHO EVOLUTION WITHIN THE HIGH RISK AREA THROUGH THE
   EVENING HOURS. WRF-ARW SIMULATION FROM 00Z TAKES THE APEX OF THE
   PROGRESSIVE MCS FROM CHICAGO TO DETROIT IN UNDER 6 HOURS WITH A
   FORWARD SPEED IN EXCESS OF 40KT. SHEAR AND INSTABILITY WITHIN AND
   AHEAD OF THIS CONVECTION WILL REMAIN SUPPORTIVE OF BOTH HIGH WINDS
   POSSIBLY WELL IN EXCESS OF 60KT...AS WELL A FEW TORNADOES POSSIBLY
   ASSOCIATED WITH SUPERCELL STRUCTURES EMBEDDED WITHIN THE SQUALL
   LINE/QLCS.

   ...OH EAST TO EAST COAST/SOUTHEAST...
   WARM MOIST AIRMASS ALSO EXISTS WELL EAST OF THE STRONGER FORCING
   ACROSS FROM OH EAST ACROSS THE APPALACHIANS TO EAST COAST. SOME
   MODEL SIMULATIONS DEPICT THE POSSIBLE EVOLUTION OF SMALL CONVECTIVE
   COMPLEXES DEVELOPING FROM INITIALLY MULTICELLULAR STORMS ACROSS THE
   HIGHER TERRAIN THIS AFTERNOON. LARGE SCALE FORCING AND SHEAR REMAIN
   SUBTLE/WEAK ACROSS THESE AREAS UNTIL LATE IN THE PERIOD.
   HOWEVER...DEGREE OF ANTICIPATED INSTABILITY COULD RESULT IN A FEW
   HAIL/WIND EVENTS THROUGH THE EVENING AND POSSIBLY INTO LATE
   TONIGHT/EARLY FRIDAY ACROSS THESE PARTS OF THE SLGT RISK AREA.

   ...MT/NERN WY...
   STRONG IMPULSES ROTATING THROUGH THE BASE OF LARGER TROUGH ACROSS
   THE PACIFIC NORTHWEST WILL AID ASCENT ACROSS THE NRN ROCKIES THROUGH
   THE AFTERNOON. STEEPENING LOW THROUGH MID-LEVEL LAPSE RATES AND
   STRENGTHENING SHEAR SHOULD CONTRIBUTE TO A NUMBER OF SUPERCELL
   STORMS POSING BOTH HAIL AND WIND THREATS. AN ISOLATED TORNADO MAY
   ALSO EVOLVE FROM INITIAL DISCRETE CELLS GIVEN RELATIVELY HIGH
   BOUNDARY LAYER MOISTURE AND SUFFICIENT DIRECTIONAL SHEAR IN THE
   STORM UPDRAFT LAYER.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z