The SPC is forecasting ...Severe thunderstorms expected over parts of the lower Mississippi and Tennessee Valleys this afternoon and tonight....   Please read the latest public statement about this event.  View What is a Watch? clip.

   SPC AC 281237

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0737 AM CDT MON APR 28 2014

   VALID 281300Z - 291200Z

   ...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF WRN AND MIDDLE
   TN...NRN AND CNTRL MS...NWRN AL...AND FAR NERN LA...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE MID MS AND OH
   VALLEYS SWD TO THE LOWER MS VALLEY AND CNTRL GULF STATES...AND EWD
   TO THE CNTRL AND SRN APPALACHIANS...

   ...SUMMARY...
   A SEVERE WEATHER OUTBREAK IS FORECAST TODAY INTO TONIGHT FROM PARTS
   OF THE LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE VALLEY AND
   CENTRAL GULF COAST STATES. NUMEROUS TORNADOES ARE EXPECTED...SOME OF
   WHICH COULD BE INTENSE. VERY LARGE HAIL AND DAMAGING STRAIGHT LINE
   WINDS ARE ALSO LIKELY.

   ...SYNOPSIS...

   AN INTENSE MID TO UPPER-LEVEL TROUGH WILL EDGE ONLY SLIGHTLY EWD
   FROM THE CNTRL PLAINS INTO THE MID MS VALLEY WITH THIS SYSTEM
   BOUNDED ON IT/S SRN PERIPHERY BY A 500-MB JET IN EXCESS OF 70-80 KT
   CURVING CYCLONICALLY FROM THE FOUR-CORNERS REGION THROUGH LOWER MS
   AND TN VALLEYS INTO CNTRL APPALACHIANS. EMBEDDED WITHIN THIS
   HIGH-MOMENTUM AIR STREAM...A MIDLEVEL JET STREAK WILL PROGRESS FROM
   THE ARKLATEX AND OZARK PLATEAU EWD INTO THE MID SOUTH. THIS
   UPPER-AIR PATTERN EVOLUTION WILL MAINTAIN A 40-50+ KT SWLY LLJ OVER
   THE CNTRL GULF STATES AND TN VALLEY...ENHANCING BOTH VERTICAL SHEAR
   AND THE POLEWARD FLUX OF HEAT AND MOISTURE WITHIN THE WARM SECTOR OF
   THE SYNOPTIC SYSTEM.

   AT THE SURFACE...AN OCCLUDED AREA OF LOW PRESSURE OVER ERN NEB WILL
   WEAKEN WHILE SLOWLY SHIFTING ACROSS SRN IA. MEANWHILE...AN
   ASSOCIATED COLD FRONT WILL GRADUALLY OVERTAKE A STALLED
   DRYLINE/PACIFIC FRONT OVER THE OZARKS INTO NERN TX BEFORE ADVANCING
   EWD THROUGH THE MID/LOWER MS VALLEY. THE TRAILING EXTENSION OF THIS
   FRONT WILL MOVE MORE SLOWLY SEWD THROUGH PARTS OF LA AND SERN/SRN
   TX. THERE IS SOME INDICATION IN LATEST MODEL GUIDANCE THAT A
   SECONDARY SURFACE LOW MAY FORM ALONG OR JUST AHEAD OF THE COLD FRONT
   OVER THE MID SOUTH TODAY WITH THIS FEATURE TRACKING NEWD INTO THE
   UPPER OH VALLEY. FINALLY...A WARM FRONT STRETCHING FROM THE MID MO
   VALLEY LOW ESEWD THROUGH THE OH VALLEY TO CAROLINAS WILL SLOWLY LIFT
   NWD.  

   ...OH/LOWER MS VALLEYS EWD TO THE SRN APPALACHIANS TODAY THROUGH
   TONIGHT...

   AS OF 12Z...REGIONAL RADAR INDICATED A COUPLE OF SEPARATE MCSS...ONE
   WITH A WELL-DEFINED MCV AND EWD/SEWD-ADVANCING COLD POOL FROM SRN
   IND/CNTRL KY SWWD THROUGH WRN TN WHERE IT INTERSECTED A MORE
   RECENTLY DEVELOPED SYSTEM WHICH TRAILED SSWWD THROUGH NWRN MS TO NRN
   LA AND ERN TX. THIS ACTIVITY WILL LIKELY CONTINUE EWD ACROSS PARTS
   OF TN...MS...LA...PERHAPS AL THIS MORNING INTO EARLY
   AFTERNOON...POSING A RISK FOR A COUPLE TORNADOES...DAMAGING WINDS
   AND LARGE HAIL BEFORE WEAKENING LATER TODAY. 

   IN THE WAKE OF THESE INITIAL STORMS...CONVECTION-ALLOWING MODEL
   GUIDANCE IS QUITE CONSISTENT IN SUGGESTING THE REDEVELOPMENT OF
   TSTMS BY AFTERNOON ALONG REMNANT OUTFLOW BOUNDARIES AND THE
   EWD-MOVING COLD FRONT FROM WRN OR MIDDLE TN SWWD THROUGH NRN/CNTRL
   MS INTO NERN LA. 12Z OBSERVED SOUNDINGS FROM THE LOWER MS VALLEY
   INDICATE THAT A PRONOUNCED EML HAS BEEN ADVECTED EWD INTO THE REGION
   WITH 700-500-MB LAPSE RATES OF 7.5-8.0 C/KM. THESE STEEP LAPSE RATES
   OVERLIE A VERY MOIST BOUNDARY LAYER /I.E. LOWEST 100-MB MEAN-MIXING
   RATIOS OF 13.5-15.5 G PER KG/ WHICH WILL PROMOTE AFTERNOON MLCAPE
   VALUES OF 1500-2500 J/KG IN AREAS WHERE STRONGER DAYTIME HEATING CAN
   OCCUR. THIS INSTABILITY WILL ALIGN WITH 50-70 KT DEEP-LAYER SHEAR
   AND EFFECTIVE SRH VALUES OF 200-300 M2/S2...SETTING THE STAGE FOR A
   POTENTIALLY VOLATILE ENVIRONMENT...SUPPORTIVE OF SUPERCELLS CAPABLE
   OF INTENSE TORNADOES AND VERY LARGE HAIL. MESOSCALE TRENDS WILL
   CONTINUE TO BE MONITORED FOR A POSSIBLE UPGRADE TO HIGH RISK LATER
   TODAY.

   THE NRN EXTENT OF THIS FAVORABLE WARM SECTOR ENVIRONMENT WILL BE
   DICTATED BY THE LINGERING EFFECTS OF THE CURRENT COLD POOL IN PLACE
   ACROSS THE LOWER OH INTO PARTS OF THE TN VALLEY. WHERE STRONGER
   BOUNDARY-LAYER HEATING CAN OCCUR...THE LARGE-SCALE ENVIRONMENT WILL
   SUPPORT SUPERCELLS CAPABLE OF TORNADOES AND LARGE HAIL NWD INTO SRN
   PARTS OF THE MID OH VALLEY.

   AN EVENTUAL UPSCALE GROWTH OF DIURNALLY ENHANCED TSTMS INTO ONE OR
   MORE LINEAR CONVECTIVE SYSTEMS APPEARS LIKELY LATE THIS EVENING INTO
   THE OVERNIGHT HOURS OVER PARTS OF THE MID OH AND TN VALLEYS SWD
   TOWARD THE CNTRL GULF COAST. THIS ACTIVITY WILL PROGRESS EWD INTO
   THE CNTRL/SRN APPALACHIANS AND ERN GULF STATES WITH A CONTINUING
   THREAT FOR PRIMARILY DAMAGING WINDS.  

   ...MID MS VALLEY THIS AFTERNOON INTO EVENING...

   ANALOGOUS TO YESTERDAY/S EVENTS OVER CNTRL NEB...A SIMILAR SETUP
   WILL EVOLVE OVER THE REGION TODAY WHEREBY THE MIDLEVEL COLD POOL
   ASSOCIATED WITH THE UPPER LOW OVERLIES A WARMING BOUNDARY
   LAYER...YIELDING STEEP LAPSE RATES AND MLCAPE OF 1000-1500 J/KG. A
   PRONOUNCED GRADIENT IN DEEP-LAYER SHEAR WILL EXIST BY
   AFTERNOON...RANGING FROM GENERALLY LESS THAN 30 KT ALONG THE
   OCCLUDED FRONT OVER SRN IA INTO W-CNTRL IL...TO 50-60 KT OVER
   CNTRL/SRN PARTS OF IL/IND AND POINTS SOUTH. AS SUCH...MIXED STORM
   MODES WILL LIKELY EVOLVE THIS AFTERNOON...INCLUDING MULTICELL AND
   SUPERCELL STRUCTURES. LARGE HAIL WILL BE THE PRIMARY HAZARD...THOUGH
   TORNADOES ARE ALSO POSSIBLE OWING TO THE PRESENCE OF A
   VERTICAL-VORTICITY-RICH ENVIRONMENT.

   ...CNTRL/ERN NC CAROLINA THIS AFTERNOON...

   DESPITE THE PRESENCE OF A BUILDING MIDLEVEL RIDGE...LOW-LEVEL
   MOISTENING COUPLED WITH DAYTIME HEATING AND CONVERGENCE ALONG THE
   SLOWLY RETREATING WEDGE FRONT MAY FOSTER AN ENVIRONMENT FAVORABLE
   FOR ISOLATED SEVERE STORMS THIS AFTERNOON. FORECAST SOUNDINGS
   INDICATE MLCAPE APPROACHING 500-1500 J/KG AND A VERTICALLY VEERING
   WIND PROFILE WITH 30-35 KT OF VERTICAL SHEAR WHICH WOULD SUPPORT
   ORGANIZED/ROTATING UPDRAFTS WITH A RISK FOR ISOLATED OCCURRENCES OF
   LARGE HAIL AND/OR LOCALLY DAMAGING WIND GUSTS.

   ..MEAD/MOSIER.. 04/28/2014

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z