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

   SPC AC 100559
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1259 AM CDT FRI APR 10 2009
   
   VALID 101200Z - 111200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTN/EARLY EVE ACROSS PARTS
   OF MIDDLE/ERN TN...NRN AL...NR GA INTO PARTS OF WRN NC/SC....
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
   AREA...FROM PARTS OF THE MID SOUTH/NRN GULF STATES INTO THE LEE OF
   THE SRN APPALACHIANS....
   
   ...SYNOPSIS...
   A CLOSED MID-LEVEL CIRCULATION IS NOW IN THE PROCESS OF FORMING
   WITHIN AN AMPLIFYING TROUGH IN THE SOUTHERN BRANCH OF SPLIT POLAR
   FLOW...OFF THE SOUTHERN CALIFORNIA COAST.  AND...MUCH OF THE MODEL
   GUIDANCE IS SIMILAR...INDICATING THAT THIS FEATURE WILL TURN
   EASTWARD ACROSS SOUTHERN CALIFORNIA INTO THE LOWER COLORADO VALLEY
   LATER TODAY/TONIGHT.  AS THIS OCCURS...UPPER RIDGING APPEARS LIKELY
   TO BUILD THROUGH MUCH OF THE PLAINS/LOWER MISSISSIPPI VALLEY AND
   CENTRAL GULF COASTAL AREAS...IN THE WAKE OF THE WEAKENING REMNANTS
   OF THE COMPACT AND VIGOROUS CLOSED LOW NOW PROGRESSING EASTWARD
   INTO/THROUGH THE OZARK PLATEAU.  JUST HOW FAST THIS LATTER SYSTEM
   WEAKENS...TO THE SOUTH OF A NORTHERN STREAM TROUGH PROGGED TO DIG
   ACROSS THE EASTERN CANADIAN PROVINCES AND UPPER GREAT LAKES
   REGION...IS A BIT UNCERTAIN.  BUT...IT WILL ENCOUNTER AT LEAST A
   SOMEWHAT MORE CONFLUENT REGIME BETWEEN THE NORTHERN AND SOUTHERN
   STREAMS...ACROSS THE LOWER OHIO/TENNESSEE VALLEYS INTO THE MID
   ATLANTIC STATES.  REGARDLESS...LOW AND MID-LEVEL JET STREAKS
   ACCOMPANYING THIS FEATURE ARE EXPECTED TO REMAIN STRONG AND
   SUFFICIENTLY SHEARED TO SUPPORT CONTINUING SEVERE POTENTIAL...AS A
   MOIST AND POTENTIALLY UNSTABLE GULF RETURN FLOW DEVELOPS THROUGH THE
   MID SOUTH AND NORTHERN GULF STATES INTO THE LEE OF THE SOUTHERN
   APPALACHIANS.
   
   ...MID SOUTH/NRN GULF STATES INTO LEE OF THE SRN APPALACHIANS...
   THE BOUNDARY LAYER OVER THE GULF OF MEXICO STILL IS IN THE PROCESS
   OF MODIFYING IN THE WAKE OF A PRIOR FRONTAL PASSAGE.  BUT...NCEP
   SREF SUGGESTS A HIGH LIKELIHOOD OF SURFACE DEW POINTS NEAR OR JUST
   ABOVE 60F RETURNING NORTHWARD INTO THE TENNESSEE VALLEY AND SOUTHERN
   APPALACHIANS...AND MID/UPPER 50S DEW POINTS FARTHER NORTH INTO THE
   LOWER OHIO VALLEY/CENTRAL APPALACHIANS TODAY.
   
   THE LEADING EDGE OF THE HIGHER MOISTURE CONTENT AIR WILL PROBABLY BE
   COINCIDENT WITH A ZONE OF ENHANCED LOWER/MID TROPOSPHERIC WARM
   ADVECTION ON THE EDGE OF SUBTROPICAL RIDGING BUILDING NORTHEASTWARD
   THROUGH THE CENTRAL/EASTERN GULF STATES.  AND...THIS
   FORCING...DOWNSTREAM OF THE BASE OF THE APPROACHING MID-LEVEL SHORT
   WAVE IMPULSE...IS EXPECTED TO PROVIDE THE FOCUS FOR INTENSE
   CONVECTIVE DEVELOPMENT BY THE AFTERNOON HOURS...ACROSS MIDDLE AND
   EASTERN TENNESSEE...MUCH OF NORTHERN ALABAMA AND GEORGIA...INTO THE
   WESTERN CAROLINAS.  LOW-LEVEL HODOGRAPHS ACROSS THIS REGION ARE
   EXPECTED TO BE LARGE AND CLOCKWISE CURVED NEAR A 30-50 KT
   SOUTHWESTERLY 850 MB JET AXIS.  AND...50-70 KT WESTERLY MID-LEVEL
   FLOW NEAR THE 500 MB JET AXIS WILL CONTRIBUTE TO STRONG DEEP LAYER
   SHEAR.  SHEAR PROFILES APPEAR QUITE FAVORABLE FOR THE EVOLUTION OF
   CLASSIC LONG LIVED SUPERCELLS...CAPABLE OF PRODUCING LARGE DAMAGING
   HAIL AND A FEW TORNADOES...IN THE PRESENCE OF THERMODYNAMIC PROFILES
   CHARACTERIZED BY STEEP LAPSE RATES WITH MIXED LAYER CAPE OF 1000-
   2000 J/KG.
   
   AT THE SAME TIME...A BAND OF STRONGER FORCING ASSOCIATED WITH THE
   MID-LEVEL CYCLONIC VORTICITY CENTER IS EXPECTED TO CONTRIBUTE TO AT
   LEAST A BROKEN LINE OF STORMS AS IT SPREADS ACROSS KENTUCKY/
   TENNESSEE DURING THE AFTERNOON HOURS...JUST AHEAD OF THE WEAKENING
   SURFACE LOW.  DEEP LAYER SHEAR ACROSS KENTUCKY...WELL NORTH OF THE
   POLAR JET AXIS...IS EXPECTED TO BE MORE MODEST THAN AREAS TO THE
   SOUTH...WITH INSTABILITY ALSO A BIT WEAKER.  BUT...LOW-LEVEL
   HODOGRAPHS WILL STILL PROBABLY BE CLOCKWISE CURVED AND
   SIZABLE...SUPPORTIVE OF A FEW EMBEDDED SUPERCELLS WITH THE ENHANCED
   RISK FOR DAMAGING WINDS/LARGE HAIL...POSSIBLY ISOLATED TORNADOES.
   
   LARGE-SCALE FORCING IN ADVANCE OF THE WEAKENING UPPER IMPULSE IS
   EXPECTED TO STRENGTHEN EAST OF THE SOUTHERN APPALACHIANS THROUGH
   REMAINDER OF THE CAROLINAS BY THIS EVENING.  BUT...WEAKER
   DESTABILIZATION...ASSOCIATED WITH A MORE LIMITED LOW-LEVEL MOISTURE
   RETURN AND THE ONSET OF DIURNAL COOLING...MAY MITIGATE SEVERE
   POTENTIAL...OR AT LEAST RESULT IN A GRADUAL DIMINISHING TREND TO
   CONVECTIVE ACTIVITY LIKELY TO SPREAD ACROSS THE REGION.
   
   ..KERR/GRAMS.. 04/10/2009
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z