Categorical Graphic
Probabilistic Tornado Graphic
Probabilistic Damaging Wind Graphic
Probabilistic Large Hail Graphic

   SPC AC 082017
   
   DAY 1 CONVECTIVE OUTLOOK CORR 1
   NWS STORM PREDICTION CENTER NORMAN OK
   0317 PM CDT FRI MAY 08 2009
   
   VALID 082000Z - 091200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM SERN OK/NERN TX EWD ACROSS
   THE MID MOS/TN VALLEYS AND INTO THE CAROLINAS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF IA/NWRN IL...
   
   CORRECTED 5% HAIL AND WIND LINES OVER THE SOUTHEAST CONUS
   
   ...TN VALLEY REGION...
   WHILE EARLIER INTENSE MCS/BOW ECHO CONTINUES TO WEAKEN WITH
   TIME...STRONG/SEVERE STORMS CONTINUE ACROSS S CENTRAL KY AND PARTS
   OF MIDDLE TN -- WITH ISOLATED SUPERCELLS CONTINUING TO DEVELOP AHEAD
   OF THE REMNANT BOW ECHO.  WITH FAVORABLE SHEAR AND A VERY
   MOIST/MODERATELY-UNSTABLE AIRMASS IN PLACE...EXPECT STORMS TO
   CONTINUE MOVING EWD TOWARD THE APPALACHIANS THROUGH THE AFTERNOON. 
   WHILE THREAT SHOULD DIMINISH THIS EVENING...POTENTIAL FOR
   STRONG/DAMAGING WINDS AND HAIL ALONG WITH ISOLATED TORNADOES WILL BE
   POSSIBLE.
   
   ...NRN TX/SERN OK/AR...
   AIRMASS REMAINS CAPPED ACROSS THIS REGION THIS AFTERNOON...BUT
   SEWD-MOVING FRONT SHOULD PROVIDE AMPLE UVV TO ALLOW STORMS TO
   DEVELOP NEAR -- OR MORE LIKELY TO THE COOL SIDE OF -- THE SURFACE
   FRONT AS IT CONTINUES SEWD ACROSS OK/N TX THIS AFTERNOON AND
   EVENING.  WITH VERY STEEP LAPSE RATES/STRONG INSTABILITY ABOVE THE
   CAPPING LAYER AND AMPLE SHEAR FOR SUPERCELLS...EXPECT VERY LARGE
   HAIL ACROSS THIS REGION.  LOCALLY-DAMAGING WINDS OR EVEN AN ISOLATED
   TORNADO WILL ALSO BE POSSIBLE WITH ANY STORMS DEVELOPING NEAR THE
   SURFACE FRONT.  CONVECTION SHOULD CONTINUE WELL INTO THE OVERNIGHT
   HOURS...AS MODEST SLY LOW-LEVEL JET CONTINUES TO PROVIDE FAVORABLE
   WARM ADVECTION/ISENTROPIC LIFT FOR CONTINUED CONVECTIVE DEVELOPMENT.
   
   ...ERN CAROLINAS...
   ISOLATED STORMS CONTINUE TO DEVELOP WITHIN MODERATELY-UNSTABLE
   AIRMASS ACROSS THE ERN CAROLINAS.  DEEP-LAYER WIND FIELD IS
   RELATIVELY MODEST...BUT SHEAR APPEARS SUFFICIENT -- GIVEN THE DEGREE
   OF INSTABILITY -- TO SUPPORT MULTICELL ORGANIZATION AND ASSOCIATED
   HAIL/WIND POTENTIAL THROUGH EARLY EVENING BEFORE STORMS DIURNALLY
   WEAKEN.
   
   ...IA/NRN IL AND VICINITY...
   MID-LEVEL SHORT-WAVE TROUGH CONTINUES MOVING EWD ACROSS THE MO
   VALLEY REGION...ALONG WITH THE ASSOCIATED SURFACE SYSTEM. 
   HOWEVER...DESTABILIZATION HAS BEEN LIMITED AHEAD OF THE FRONT...WITH
   AOB 500 J/KG MIXED-LAYER CAPE EVIDENT ACROSS PARTS OF IA ATTM. 
   STORMS HAVE DEVELOPED OVER WRN/CENTRAL IA THIS AFTERNOON...AND GIVEN
   FAVORABLE SHEAR IN PLACE EXPECT STRONG/LOCALLY-SEVERE STORMS TO
   CONTINUE EWD TOWARD NRN IL.  GIVEN LIMITED INSTABILITY
   HOWEVER...STORM INTENSITY AND ASSOCIATED SEVERE POTENTIAL SHOULD
   WANE WITH THE LOSS OF DAYTIME HEATING AS STORMS CROSS NRN IL AND
   PERHAPS SRN WI.
   
   ..GOSS.. 05/08/2009
   
   .PREV DISCUSSION... /ISSUED 1212 PM CDT FRI MAY 08 2009/
   
   ...TN/LOWER OH VALLEY...
   LONG LIVED BOW ECHO...MOVING EWD AT 60 KT...WAS APPROACHING THE MS
   RIVER AND IS EXPECTED TO TRACK MOSTLY EWD THROUGH THE REGION THIS
   AFTERNOON. THOUGH MESOSCALE MODELS SUGGEST WEAKENING WITH
   TIME...GIVEN THE WELL ORGANIZED SYSTEM MOVING INTO AN ENVIRONMENT
   WITH STRONG INSTABILITY...MLCAPES 2000-2500 J/KG...AND EFFECTIVE
   SHEAR NEAR 40 KT IS EXPECTED TO SUSTAIN WIDESPREAD WIND
   DAMAGE..SOMETIMES EXTREME. WIND AND HAIL IS FORECAST WITH THE SYSTEM
   UNTIL IT REACHES THE APPALACHIANS THIS EVENING. LOW LEVEL SHEAR WILL
   ALSO BE SUPPORTIVE OF TORNADOES...ESPECIALLY WITH THE ROTATING BOW
   HEADS.
   
   ...NRN TX/SERN OK/AR/NRN LA...
   COLD FRONT AT MID MORNING EXTENDED FROM SERN KS SWWD INTO WRN TX
   NEAR LBB. FRONT IS EXPECTED TO MOVE SEWD TO NEAR A SGF-ADM-MAF LINE
   BY 23Z. MORNING SOUNDINGS SHOWED STRONG CAPPING BETWEEN 850-700
   MB...AND THIS SHOULD LIMIT CONVECTION ALONG THE FRONT THROUGH MOST
   OF THE DAY. DESPITE NO REAL DISCERNABLE SHORTWAVE TROUGH...MODELS
   DEPICT A SPEED MAX MOVING INTO THE REGION LATE THIS AFTERNOON WITH
   INCREASING DIFFLUENCE ALOFT. THIS WOULD RESULT IN STRENGTHENING LOW
   LEVEL CONVERGENCE ALONG THE FRONT... ESPECIALLY IN AND WEST OF THE
   ARKLATEX. ALL OPERATIONAL/MESOSCALE MODELS SHOW CONVECTION DEVELOPS
   ALONG THE FRONT IN ERN OK/NRN TX AFTER 22Z. STORMS THAT DEVELOP ARE
   LIKELY TO QUICKLY BECOME SEVERE GIVEN MLCAPES FROM 3000 TO 4000 J/KG
   AND MID LEVEL LAPSE RATES NEAR 9 C/KM INDICATE VERY LARGE HAIL WOULD
   BE THE MAIN THREAT.
   
   ...CAROLINAS.....
   REMNANT MCS FROM WRN NC INTO NERN GA IS EXPECTED TO CONTINUE EWD
   INTO A MOIST AND DESTABILIZING AIR MASS...2000 J/KG MLCAPE WITH 
   TEMPERATURES IN THE 80S. ALTHOUGH ACTIVITY WILL GRADUALLY DEVELOP
   SOUTH OF THE STRONGER WINDS ALOFT...UNIDIRECTIONAL WLY WINDS AT 20
   TO 30 KT THROUGH THE LOWER 6 KM MAY SUPPORT A LINEAR SYSTEM THIS
   AFTERNOON...WITH WIND DAMAGE THE PRIMARY THREAT.
   
   ...IA/NWRN IL AND SWRN WI...
   A STRONG SHORTWAVE TROUGH OVER CENTRAL NEB/SD WILL TRACK EWD TO NEAR
   THE NEB/IA BORDER BY 00Z. COLD TEMPERATURES ALOFT...500 MB
   TEMPERATURES FROM -18 TO -22C...MODERATELY STEEP LAPSE RATES...40-50
   KT DEEP LAYER SHEAR AND LIFT ASSOCIATED WITH TROUGH/ASSOCIATED JET
   MAX SHOULD RESULT IN SUPERCELLS. HAIL AND WIND DAMAGE WILL BE THE
   MAIN THREATS.
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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