Apr 4, 2011 2000 UTC Day 1 Convective Outlook
Updated: Mon Apr 4 19:56:44 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the parts of the lower ms and tn valleys this afternoon....   Please read the latest public statement about this event.

Categorical Graphic
20110404 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110404 2000 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20110404 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20110404 2000 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 041953
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0253 PM CDT MON APR 04 2011
   
   VALID 042000Z - 051200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS
   PARTS OF EASTERN MISSISSIPPI....MUCH OF ALABAMA...NORTHWEST
   GEORGIA...MIDDLE AND EASTERN TENNESSEE...SOUTHEAST
   KENTUCKY...SOUTHWEST VIRGINIA AND PARTS OF WRN NORTH CAROLINA...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
   AREA...EAST OF THE LOWER MISSISSIPPI VALLEY THROUGH AND TO THE LEE
   OF THE APPALACHIANS...
   
   ...20Z UPDATE...
   
   THE MODERATE RISK AREA HAS BEEN EXPANDED NORTHEASTWARD AND EASTWARD
   THROUGH PORTIONS OF THE CENTRAL APPALACHIANS...CUMBERLAND
   PLATEAU...AND EASTERN GULF STATES...DOWNSTREAM OF AN EXTENSIVE
   EVOLVING PRE-FRONTAL SQUALL LINE.  HEADING INTO THE PEAK HEATING
   HOURS...SUFFICIENT DESTABILIZATION IS EXPECTED TO MAINTAIN VIGOROUS
   CONVECTIVE DEVELOPMENT IN THE PRESENCE OF 50+ KT SOUTH SOUTHWESTERLY
   DEEP LAYER MEAN FLOW.  
   
   A SEGMENT OF THE SQUALL LINE IS CURRENTLY SURGING ACROSS MIDDLE
   TENNESSEE AND PORTIONS OF ADJACENT STATES AROUND 60+ KTS...AND
   APPEARS LIKELY TO CONTINUE NORTHEASTWARD THROUGH THE CUMBERLAND
   PLATEAU AND WESTERN SLOPES OF THE CENTRAL APPALACHIANS BY 22-23Z
   ...ACCOMPANIED BY THE CONTINUED RISK FOR VERY STRONG AND DAMAGING
   WIND GUSTS.  GRADUALLY...AS A SIGNIFICANT SHORT WAVE IMPULSE DIGS
   SOUTHEAST OF THE SOUTH CENTRAL PLAINS AND UPPER PORTIONS OF THE
   LOWER MISSISSIPPI VALLEY...BEFORE TURNING EASTWARD LATER
   TONIGHT...BACKING UPPER FLOW AND A MORE STABLE ENVIRONMENT MAY
   CONTRIBUTE TO WEAKENING OF THE CONVECTIVE SYSTEM TO THE EAST OF THE
   CENTRAL APPALACHIANS.  HOWEVER...VEERING OF THE MID-LEVEL FLOW
   FIELDS BY LATE EVENING EAST OF THE LOWER MISSISSIPPI VALLEY INTO THE
   EASTERN GULF STATES MAY SUPPORT ANOTHER SURGING SEGMENT... CAPABLE
   OF PRODUCING WIDESPREAD DAMAGING WIND GUSTS ACROSS MUCH OF
   NORTHERN/CENTRAL ALABAMA INTO NORTHERN GEORGIA.  DESPITE THE
   UNFAVORABLE TIME OF TIME...A MORE MOIST AND INCREASINGLY STRONGLY
   HEATED BOUNDARY LAYER WILL PROBABLY BE SLOW TO STABILIZE.
   
   TORNADO POTENTIAL REMAINS A BIT MORE UNCLEAR.  DISCRETE SUPERCELL
   DEVELOPMENT APPEARS A POSSIBILITY WITHIN A ZONE OF ENHANCE LOW-LEVEL
   WARM ADVECTION AHEAD OF THE SOUTHERN FLANK OF THE SQUALL
   LINE...ACROSS PARTS OF SOUTH CENTRAL/EASTERN CENTRAL ALABAMA THIS
   EVENING.  IF THIS OCCURS...VERY LARGE...CLOCKWISE CURVED LOW-LEVEL
   HODOGRAPHS WILL SUPPORT A RISK FOR TORNADOES.
   
   ..KERR.. 04/04/2011
   
   .PREV DISCUSSION... /ISSUED 1129 AM CDT MON APR 04 2011/
   
   ...OH/TN/LOWER MS VALLEY AND CNTRL GULF COAST THROUGH TONIGHT...
   ONGOING TSTM COMPLEXES WITH MIXED STORM MODES...INCLUDING
   LINEAR/BOWING SEGMENTS AND EMBEDDED SUPERCELL MORPHOLOGIES CONTINUE
   ALONG AND JUST AHEAD OF SHARP COLD FRONT FROM ERN IND S/SWWD INTO
   SERN TX. REFERENCE MCD/S AND WW/S FOR ADDITIONAL SHORT-TERM
   DISCUSSION.
   
   PERSISTENT BOUNDARY LAYER MOISTENING ALONG AXIS OF 50-70 KT SWLY LLJ
   COUPLED WITH MODEST HEATING WILL CONTRIBUTE TO AFTERNOON MLCAPE
   VALUES FROM 250-1000 J/KG OVER THE TN/OH VALLEY TO 1000-2000 J/KG
   ACROSS PARTS OF THE LOWER MS VALLEY AND CNTRL GULF COAST STATES.
   GIVEN THE STRONG LOW/DEEP-LAYER SHEAR OBSERVED AHEAD OF THE COLD
   FRONT...AND CONTINUED UPSCALE ORGANIZATION INTO LINEAR STORM
   MODES...ONE OR MORE LONG-LIVED QLCS/S REMAINS PROBABLE FROM THE TN
   VALLEY INTO THE LOWER MS VALLEY WITH WIDESPREAD DAMAGING WINDS AND A
   FEW TORNADOES ACROSS THE MODERATE RISK AREA. THE DAMAGING WIND
   THREAT WILL CONTINUE THIS EVENING INTO TONIGHT ACROSS THE DEEP SOUTH
   INTO THE SOUTHEAST IN CONCERT WITH THE QLCS MOVING THROUGH THE AREA.
   
   ...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.
   
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