Apr 28, 2014 2000 UTC Day 1 Convective Outlook
Updated: Mon Apr 28 19:23:43 UTC 2014 (20140428 2000Z Day 1 shapefile | 20140428 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

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.

Categorical Graphic
20140428 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20140428 2000 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20140428 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20140428 2000 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
HIGH 21,117 1,423,065 Jackson, MS...Florence, AL...Tupelo, MS...Fayette, AL...
MODERATE 38,271 2,540,811 Huntsville, AL...Meridian, MS...Natchez, MS...Grenada, MS...
SLIGHT 335,384 45,090,292 Indianapolis, IN...Charlotte, NC...Memphis, TN...Nashville, TN...Louisville, KY...
   SPC AC 281919

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0219 PM CDT MON APR 28 2014

   VALID 282000Z - 291200Z

   ...THERE IS A HIGH RISK OF SVR TSTMS ACROSS PORTIONS OF MS...AL...

   ...THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK AREA
   ACROSS PORTIONS OF LA...MS...AL...TN...

   ...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE ACROSS A LARGE AREA
   FROM THE LOWER/MID MS VALLEY EWD TO THE SRN APPALACHIANS AND
   CAROLINAS...

   ...SUMMARY...
   A SEVERE WEATHER OUTBREAK WILL CONTINUE THROUGH 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.

   ...PRIMARY CHANGES TO THE DAY 1 CONVECTIVE OUTLOOK...
   /1/ AREAS FROM CNTRL MS TO NWRN AL HAVE BEEN UPGRADED TO HIGH RISK
   FOR A TORNADO OUTBREAK. SEMI-DISCRETE/DISCRETE SUPERCELLS ARE
   EVOLVING ALONG A PRE-FRONTAL CONFLUENCE AXIS STRETCHING FROM N-CNTRL
   MS TO W-CNTRL MS. ADDITIONAL CONVECTION SHOULD FORM FARTHER S WITH
   DIURNAL HEATING...WITH ALL OF THIS ACTIVITY PROGRESSING EWD ACROSS
   PARTS OF MS INTO WRN AL. WITH WARM/MOIST BOUNDARY-LAYER CONDITIONS
   SUPPORTING MLCAPE AROUND 2000-2500 J/KG AMIDST 200-400 M2/S2 OF
   EFFECTIVE SRH...AND GIVEN THE PRESENCE OF SEPARATED/ROTATING
   UPDRAFTS...CONFIDENCE HAS INCREASED IN GREATER COVERAGE OF TORNADOES
   WARRANTING THE HIGH RISK UPGRADE. SIGNIFICANT TORNADOES ARE
   EXPECTED.

   /2/ MINOR ADJUSTMENTS HAVE TO THE MODERATE RISK TO INCLUDE MORE OF
   NERN LA...SRN MS...AND WRN/CNTRL AL TO ACCOUNT FOR HIGHER SEVERE
   THUNDERSTORM/TORNADO POTENTIAL WITH CONVECTION DEVELOPING ALONG THE
   FRONT/DRYLINE OVER THE SABINE VALLEY...WITH THE GREATER SVR RISK
   SPREADING EWD ACROSS AL TONIGHT.

   /3/ THE SLIGHT RISK AREA WAS EXTENDED NEWD INTO PORTIONS OF ERN
   KY...WRN VA...AND VICINITY FOR SVR WIND AND TORNADO RISK SHIFTING
   ENEWD THROUGH THE AFTERNOON.

   ..COHEN.. 04/28/2014

   .PREV DISCUSSION... /ISSUED 1146 AM CDT MON APR 28 2014/

   ...SYNOPSIS...
   A CLOSED/OCCLUDED LOW OVER ERN NEB WILL WOBBLE EWD ACROSS IA/NRN MO
   AS SERIES OF EMBEDDED SPEED MAXIMA ROTATE AROUND THE SRN AND ERN
   PERIPHERY OF THE LOW.  AT THE SURFACE...THE WARM SECTOR EXTENDS AS
   FAR N/NW AS CENTRAL IL AND SRN IA...THOUGH THE RICHER MOISTURE AND
   GREATER BUOYANCY WILL BE CONFINED TO THE LA/MS/AL AREA TODAY.  THE
   MAIN SEVERE THREATS THIS AFTERNOON WILL BE CONFINED TO TWO CORRIDORS
   - A SUPERCELL/TORNADO RISK FROM MS ACROSS NW AL/SRN MIDDLE TN...AND
   AN ARC OF STORMS WITHIN THE DRY SLOT FROM SRN IA TO CENTRAL IL.

   ...MS/AL/TN THIS AFTERNOON THROUGH TONIGHT...
   MORNING STORMS HAVE BEEN WEAKENING...LEAVING AN OUTFLOW BOUNDARY
   THAT IS BETTER-DEFINED ACROSS SRN MIDDLE TN...AND MORE DIFFUSE WITH
   SWWD EXTENT ACROSS NW MS TO NE LA.  CLEARING OF THE MORNING CLOUD
   DEBRIS IS ALSO ALLOWING STRONGER SURFACE HEATING TO COMMENCE FROM LA
   INTO SW MS...WITH ADDITIONAL CLEARING EXPECTED BY EARLY AFTERNOON
   ACROSS NE MS AND NW AL.  BY EARLY AFTERNOON...WEAKENING OF
   CONVECTIVE INHIBITION SHOULD ALLOW RENEWED STORM DEVELOPMENT ALONG
   OR JUST E OF THE RESIDUAL OUTFLOW BOUNDARY FROM NE LA NEWD ACROSS MS
   AND NW AL TO SRN MIDDLE TN BY EARLY-MID AFTERNOON.  THE STORM
   ENVIRONMENT WILL BE CHARACTERIZED BY MLCAPE NEAR 2000
   J/KG...EFFECTIVE BULK SHEAR OF 50-60 KT...EFFECTIVE SRH OF 200-300
   MS2/S2...AND A MOIST BOUNDARY LAYER.  GIVEN THE SUBTLE FORCING FOR
   ASCENT...A DISCRETE OR CLUSTER SUPERCELL MODE APPEARS LIKELY...WITH
   THE POTENTIAL FOR SEVERAL STRONG AND LONG-TRACK TORNADOES THIS
   AFTERNOON/EVENING FROM CENTRAL MS NEWD TO NW AL.  THIS AREA WILL BE
   MONITORED CAREFULLY FOR A HIGH RISK UPGRADE IN A NARROW CORRIDOR BY
   20Z.

   BY LATE EVENING AND OVERNIGHT...CONVECTION SHOULD EVOLVE INTO A BAND
   OF STORMS WITH EMBEDDED SUPERCELLS AND BOWING SEGMENTS...WITH A
   CONTINUED RISK FOR A FEW TORNADOES...DAMAGING WINDS...AND LARGE HAIL
   WELL INTO THE OVERNIGHT HOURS ACROSS ERN TN...NW GA...AL AND
   CENTRAL/SRN MS. 

   ...ERN MO/WRN IL INTO SRN IA THIS AFTERNOON...
   A BROKEN ARC OF THUNDERSTORMS WILL FORM THIS AFTERNOON ALONG THE
   SURFACE FRONT FROM ERN MO NWD AND NWWD INTO SRN IA...WITH STORMS
   EXPECTED TO SPREAD INTO W CENTRAL IL DURING THE LATE
   AFTERNOON/EVENING.  SOME LOW-TOPPED SUPERCELLS WILL BE POSSIBLE IN
   AN ENVIRONMENT WITH VERY STEEP LAPSE RATES AND MARGINALLY FAVORABLE
   SHEAR...WHICH WILL SUPPORT A RISK FOR LARGE HAIL/DAMAGING WINDS AND
   A COUPLE TORNADOES.

   ...SRN NC/NRN SC THIS AFTERNOON...
   ISOLATED STRONG/SEVERE STORM DEVELOPMENT WILL BE POSSIBLE ALONG THE
   STALLED FRONT THIS AFTERNOON...WHERE LOW-MIDLEVEL VERTICAL SHEAR
   WILL BE SUFFICIENT FOR ORGANIZED CLUSTERS.  MODERATE INSTABILITY
   ALONG THE FRONT AND SEA BREEZE WILL SUPPORT A RISK FOR LARGE
   HAIL/DAMAGING WINDS.

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