Apr 27, 2012 1730 UTC Day 2 Convective Outlook
Updated: Fri Apr 27 17:30:40 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120427 1730 UTC Day 2 Outlook Graphic
Probabilistic Graphic
20120427 1730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
   SPC AC 271728
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1228 PM CDT FRI APR 27 2012
   
   VALID 281200Z - 291200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE OH VALLEY
   INTO SERN MO...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PART OF THE SRN
   PLAINS...
   
   ...SYNOPSIS...
   BLOCKING UPPER LEVEL FLOW WILL PERSIST THROUGH D2 FROM CANADA INTO
   THE NRN THIRD TO ONE HALF OF THE CONUS AS A STRONG RIDGE REMAINS
   CENTERED OVER CENTRAL CANADA...AND EXTENDS SSEWD INTO THE GULF COAST
   STATES WITH LESS AMPLITUDE.  CLOSED LOWS WILL FLANK THIS RIDGE...1/
   MOVING SLOWLY NWD THROUGH THE NRN PLAINS...AND 2/ A MUCH LARGER
   SYSTEM ENCOMPASSING ERN CANADA INTO THE NERN STATES. 
   MEANWHILE...MODELS ARE IN AGREEMENT WITH THE WEAKENING OF THE
   COMPACT D1 SHORTWAVE TROUGH AS IT MOVES QUICKLY FROM THE UPPER MS
   VALLEY THROUGH THE LOWER GREAT LAKES AND BASE OF THE ERN CANADA
   CLOSED LOW.  MODELS TEND TO AGREE WITH THE TIMING OF A MORE SUBTLE
   MIDLEVEL IMPULSE TRACKING THROUGH THE GREAT BASIN AND SRN ROCKIES D1
   AND INTO THE MID MS/OH VALLEYS ON SAT.  
   
   A WARM FRONT WILL LIFT NWD TO NEAR THE OH RIVER...BUT NWD PROGRESS
   WILL BE IMPEDED BY A SURFACE HIGH PRESSURE CENTERED OVER ONTARIO
   EXTENDING SWD ACROSS THE GREAT LAKES.  THE EJECTING BUT DEAMPLIFYING
   WAVE WILL PROVIDE IMPETUS FOR AN ATTENDANT SURFACE LOW TO TRACK SEWD
   FROM NRN MO INTO THE LOWER OH VALLEY TO KY...WHILE A TRAILING COLD
   FRONT ADVANCES SEWD.  BY THE END OF THE PERIOD...THE LOW SHOULD BE
   LOCATED E OF THE CENTRAL APPALACHIANS WITH THE COLD FRONT EXTENDING
   SWWD THROUGH THE TN VALLEY TO OK...WHERE IT WILL BE RETREATING NWD
   AS A WARM FRONT IN THE SRN PLAINS. 
   
   ...KY/SRN IND/SRN IL/PART OF SERN MO...
   ELEVATED SHOWERS AND TSTMS SHOULD BE IN PROGRESS FROM THE UPPER MS
   VALLEY INTO A PORTION OF THE OH VALLEY WITHIN ZONE OF ISENTROPIC
   ASCENT NORTH OF THE WARM FRONT SAT MORNING. ACTIVITY WILL SHIFT
   ENEWD DURING THE DAY AND LIKELY REINFORCE THE WARM FRONT AND SLOW
   ITS NWD PROGRESS. ATMOSPHERE WILL DESTABILIZE SOUTH OF THIS FEATURE
   AS AXIS OF LOW 60S DEWPOINTS ADVECT NEWD BENEATH PLUME OF STEEPER
   MID LEVEL LAPSE RATES.  DISSIPATING LOW CLOUDS IN THE WARM SECTOR BY
   LATE MORNING OR AFTERNOON SHOULD ALLOW THE BOUNDARY LAYER TO
   DESTABILIZE WITH MLCAPE TO 1500 J/KG. POTENTIAL WILL EXIST FOR A FEW
   STORMS TO REDEVELOP ALONG THE CONVECTIVELY REINFORCED WARM FRONT...
   ESPECIALLY FROM SRN IL...SRN IND INTO THE NRN HALF OF KY WHERE
   SHORTWAVE RIDGE WILL BE SUPPRESSED SOME BY THE SUBTLE SHORTWAVE
   TROUGH. THIS REGION WILL ALSO REMAIN ON NRN FRINGE OF EML WHERE THE
   CAP SHOULD BE SOMEWHAT WEAKER THAN FARTHER SOUTH. OTHER STORMS MAY
   DEVELOP ALONG THE COLD FRONT AS IT ADVANCES SEWD. WLY UNIDIRECTIONAL
   SHEAR FROM 40-50 KT WILL SUPPORT ORGANIZATION INCLUDING A FEW
   SUPERCELLS WITH DAMAGING WIND AND LARGE HAIL THE MAIN THREATS.  
   
   FORECAST SOUNDINGS SUGGEST THE POTENTIAL FOR HAILSTONES UP TO...OR
   LOCALLY EXCEEDING...2 INCHES IN DIAMETER DUE TO STEEP MIDLEVEL LAPSE
   RATES /7.5-8 C PER KM/ ACCOMPANYING THE WEAKER MIDLEVEL IMPULSE. 
   HOWEVER...UNCERTAINTY IN THE COVERAGE OF THIS GREATER THREAT
   PRECLUDES THE INTRODUCTION OF SIGNIFICANT PROBABILITIES AT THIS
   TIME.
   
   ...OK/N TX WWD THROUGH THE TX PANHANDLE...
   TSTM POTENTIAL IS EXPECTED TO REMAIN LIMITED DURING THE DAY ALONG
   STALLING FRONT FROM NRN TX INTO THE OZARKS/SRN MO DUE TO A CAPPING
   INVERSION AND WEAK FRONTAL CONVERGENCE. THEREAFTER...A STRENGTHENING
   SLY NOCTURNAL LLJ WILL CONTRIBUTE TO NWD DESTABILIZATION OVER THE
   SRN PLAINS FROM N TX AND OK INTO THE PANHANDLES. ELEVATED STORMS
   WILL LIKELY DEVELOP WITHIN THIS ZONE OF ISENTROPIC ASCENT/STRONG WAA
   SATURDAY NIGHT.  A BAND OF 40-50 KT SWLY MIDLEVEL WINDS EXTENDING
   FROM NM ACROSS OK/SRN KS WILL RESULT IN EFFECTIVE BULK SHEAR
   BECOMING MORE FAVORABLE /40-50 KT/ TO SUPPORT ORGANIZED STORMS. 
   ACTIVITY SHOULD DEVELOP FROM S-N WITH MODELS NOW INDICATING STRONGER
   MUCAPE 1000-1500 J/KG SAT NIGHT/EARLY SUN MORNING.  THIS COMBINED
   WITH STEEP MIDLEVEL LAPSE RATES SHOULD PROMOTE STORMS PRODUCING
   SEVERE HAIL.  THE GREATEST POTENTIAL FOR SEVERE STORMS WILL BE FROM
   CENTRAL/SWRN OK INTO ERN PARTS OF THE TX PANHANDLE...AND THUS...A
   SLIGHT RISK AREA HAS BEEN INTRODUCED FOR THIS REGION SAT NIGHT.
   
   THERE IS SOME INDICATION FOR SURFACE BASED STORMS SAT EVENING INTO
   THE OVERNIGHT PERIOD...BUT CONFIDENCE IS LOWER WITH THIS THREAT.  IF
   STORMS CAN BECOME SURFACE BASED...THEN THERE WOULD BE A THREAT FOR
   DAMAGING WINDS AND A TORNADO THREAT COULD NOT BE RULED OUT.
   
   ..PETERS.. 04/27/2012
   
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