The SPC is forecasting ...severe thunderstorms expected over parts of the upper midwest into the ohio valley this afternoon and tonight.... Please read the latest public statement about this event. View What is a Watch? clip.
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| Probabilistic Tornado Graphic | |||||||||||||||||
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| 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. |
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| Probabilistic Damaging Wind Graphic | |||||||||||||||||
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| 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. |
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| Probabilistic Large Hail Graphic | |||||||||||||||||
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| 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. |
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SPC AC 121626 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1126 AM CDT WED JUN 12 2013 VALID 121630Z - 131200Z ...THERE IS A HIGH RISK OF SVR TSTMS FROM EXTREME EASTERN IOWA ACROSS NORTHERN ILLINOIS/INDIANA AND EXTREME SOUTHWEST LOWER MICHIGAN AND NORTHWEST OHIO... ...THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK AREA FROM EASTERN IOWA TO WESTERN OHIO... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA FROM THE CNTRL PLAINS/MIDWEST TO EAST COAST AND PARTS OF THE SRN APPALACHIANS... ...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF MT AND A PART OF NERN WY... ...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. ..CARBIN/SMITH/BUNTING.. 06/12/2013 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z |