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

   SPC AC 041311
   
   DAY 1 CONVECTIVE OUTLOOK CORR 1
   NWS STORM PREDICTION CENTER NORMAN OK
   0811 AM CDT MON APR 04 2011
   
   VALID 041300Z - 051200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER NRN AND CNTRL MS...FAR NERN
   LA...FAR SERN AR...PARTS OF WRN AND MIDDLE TN AND PARTS OF WESTERN
   AND NORTHERN AL...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE LOWER
   GREAT LAKES AND MID ATLANTIC STATES TO THE GULF COAST STATES...
   
   CORRECTED FOR HEADLINE FOR MDT RISK AREA
   
   ...A WIDESPREAD DAMAGING WIND EVENT APPEARS LIKELY TODAY INTO
   TONIGHT OVER PORTIONS OF THE LOWER MS VALLEY...TN VALLEY AND CNTRL
   GULF STATES...
   
   ...SYNOPSIS...
   
   POSITIVELY-TILTED LARGE-SCALE TROUGH INITIALLY FROM THE UPPER GREAT
   LAKES INTO SRN HIGH PLAINS WILL PROGRESS EWD...GRADUALLY ASSUMING A
   NEUTRAL TO SLIGHTLY NEGATIVE TILT AS IT APPROACHES THE APPALACHIANS
   LATE TONIGHT INTO TUESDAY MORNING.  POTENT VORTICITY MAXIMUM OVER
   THE SRN HIGH PLAINS /WHICH COMPRISES BASAL PORTION OF SYNOPTIC-SCALE
   TROUGH/ WILL ACCORDINGLY TRANSLATE EWD...FOCUSING A CORRIDOR OF
   STRONG DYNAMIC FORCING FROM THE SRN PLAINS AND LOWER MS VALLEY EWD
   THROUGH THE TN VALLEY AND CNTRL/SRN GULF COAST STATES.
   
   AT THE SURFACE...PRIMARY CYCLONE OVER LOWER MI WILL UNDERGO
   OCCLUSION WHILE DEVELOPING NEWD INTO QUEBEC.  ASSOCIATED WARM FRONT
   WILL RAPIDLY LIFT NEWD THROUGH THE LOWER GREAT LAKES AND NEW ENGLAND
   WHILE TRAILING COLD FRONT SURGES EWD. BY LATE AFTERNOON...THE COLD
   FRONT IS EXPECTED TO STRETCH FROM SWRN ONTARIO SWWD THROUGH CNTRL
   PARTS OF OH AND KY...WRN TN...WRN MS AND CNTRL LA.  THIS FRONT WILL
   CONTINUE EWD TONIGHT...EVENTUALLY REACHING THE PIEDMONT OR COASTAL
   PLAIN BY 05/12Z.
   
   ...AR/ERN TX EWD THROUGH THE LOWER MS VALLEY...TN VALLEY AND CNTRL
   GULF STATES TODAY INTO TONIGHT...
   
   THE INCIPIENT STAGE OF WHAT APPEARS TO BE A LONG-LIVED SEVERE
   CONVECTIVE EVENT IS CURRENTLY UNFOLDING ALONG THE COLD FRONT FROM
   THE LOWER OH VALLEY SWWD INTO NERN/N-CNTRL TX.  12Z OBSERVED
   SOUNDINGS INDICATE THAT CAP ASSOCIATED WITH THE EML HAS BEEN
   MAINTAINED GENERALLY SOUTH OF THE I-20 CORRIDOR.  HOWEVER...
   CONTINUED BOUNDARY LAYER MOISTENING ALONG AXIS OF 50-60 KT SWLY LLJ
   COUPLED WITH DAYTIME HEATING WILL CONTRIBUTE TO EVENTUAL EROSION OF
   THE CAP WITHIN WARM SECTOR WHERE AFTERNOON MLCAPE VALUES WILL RANGE
   FROM 500-1000 J/KG OVER THE TN VALLEY TO 1000-2000 J/KG ACROSS PARTS
   OF THE LOWER MS VALLEY AND CNTRL GULF STATES.
   
   CURRENT RADAR OBSERVATIONS INDICATE A MIX OF STORM MODES...INCLUDING
   LINE SEGMENTS AND SOME SUPERCELL MORPHOLOGIES.  GIVEN THE STRONG
   LOW- AND DEEP-LAYER SHEAR OBSERVED AHEAD OF THE COLD FRONT...A RISK
   FOR A FEW TORNADOES...DAMAGING WINDS AND HAIL WILL EXIST WITH THE
   MOST INTENSE STORMS THIS MORNING.  BY AFTERNOON...CONSENSUS OF
   LATEST CONVECTION-ALLOWING MODEL GUIDANCE INDICATES UPSCALE GROWTH
   OF STORMS INTO A QLCS WHICH WILL PROGRESS EWD/SEWD THROUGH THE
   MODERATE RISK AREA.  GIVEN THE FORECAST STRENGTHENING OF
   TROPOSPHERIC WIND FIELD /I.E. 50-75 KT AT 700 MB AND 50-60 KT AT 850
   MB/...THE POTENTIAL WILL EXIST FOR WIDESPREAD DAMAGING WINDS AND
   PERHAPS A FEW TORNADOES.
   
   EXPECT THE DAMAGING WIND THREAT TO CONTINUE TONIGHT ACROSS PORTIONS
   OF GA...CNTRL/SRN AL AND NRN FL IN CONCERT WITH PRE-FRONTAL QLCS
   MOVING THROUGH THE AREA.
   
   ...OH VALLEY INTO LOWER GREAT LAKES TODAY...
   
   A PRE-FRONTAL BAND OF TSTMS /SOME SEVERE/ IS IN PROGRESS THIS
   MORNING OVER PORTIONS OF OH/IND WITHIN A ZONE OF WARM THERMAL AND
   MOISTURE ADVECTIONS WHICH IS BEING ENHANCED `BY A 50-60+ KT WSWLY
   LLJ.  EARLY VISIBLE SATELLITE IMAGERY INDICATES THAT WIDESPREAD
   CLOUDINESS WILL SLOW THE DESTABILIZATION PROCESS DOWNSTREAM. 
   NONETHELESS...LATEST MODEL GUIDANCE DOES INDICATE THAT AT LEAST WEAK
   INSTABILITY WILL DEVELOP INTO THE LOWER GREAT LAKES TODAY WITH
   SBCAPE INCREASING TO A FEW HUNDRED J/KG.  GIVEN THE STRONG WIND
   FIELD IN PLACE...ANY MORE ROBUST STORMS WILL BE CAPABLE OF DAMAGING
   WIND GUSTS.
   
   ...APPALACHIANS INTO PIEDMONT AND COASTAL PLAIN LATER TONIGHT INTO
   TUESDAY MORNING...
   
   STRONG AND DEEP ASCENT AHEAD OF DYNAMIC MIDLEVEL TROUGH IS EXPECTED
   TO MAINTAIN A BAND OF LOW-TOPPED TSTMS ALONG COLD FRONT PROGRESSING
   THROUGH THE REGION.  WHILE AMBIENT AIR MASS WILL ONLY BE MARGINALLY
   UNSTABLE...BACKGROUND FORCING WILL BE FURTHER ENHANCED BY A WEAK
   FRONTAL WAVE WHICH IS FORECAST TO DEVELOP NNEWD IN THE LEE OF THE
   BLUE RIDGE AFTER 05/06Z.  GIVEN THE RAPID STRENGTHENING OF THE DEEP
   SSWLY FLOW FIELD WHICH IS FORECAST E OF THE HIGHER TERRAIN...A RISK
   OF DAMAGING WINDS WILL EXIST WITH THE LOW-TOPPED CONVECTIVE BAND.
   
   ..SELECT A FORECASTER.. 04/04/2011
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z