Apr 22, 2011 1730 UTC Day 2 Convective Outlook
Updated: Fri Apr 22 17:31:59 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20110422 1730 UTC Day 2 Outlook Graphic
Probabilistic Graphic
20110422 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 221729
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1229 PM CDT FRI APR 22 2011
   
   VALID 231200Z - 241200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM WRN KY/NWRN TN SWWD TO
   CENTRAL TX...
   
   ...SYNOPSIS...
   PROMINENT SHORTWAVE TROUGH...CURRENTLY MOVING THROUGH SD PER WATER
   VAPOR IMAGERY....WILL REMAIN PROGRESSIVE DAY 2 TRACKING FROM THE
   GREAT LAKES THROUGH SRN QUEBEC AND NRN NEW ENGLAND.  A SECOND
   TROUGH...GIVEN CLOSE PROXIMITY TO THE LEAD TROUGH IS EXPECTED TO
   WEAKEN SIGNIFICANTLY AS IT MOVES INTO CONFLUENT FLOW REGIME OVER THE
   GREAT LAKES/SRN ONTARIO.
   
   AT THE SURFACE...A THE NRN EXTENT OF A COLD FRONT ATTENDANT TO THE
   LEAD NRN STREAM MIDLEVEL TROUGH WILL MOVE EWD FROM THE LOWER GREAT
   LAKES AND OH SATURDAY MORNING...AND ACROSS MUCH OF NEW ENGLAND
   SATURDAY NIGHT.  THE TRAILING PORTION OF THIS FRONT IS EXPECTED TO
   STALL FROM THE LOWER OH VALLEY THROUGH THE OZARKS TO CENTRAL/SRN OK
   INTO THE TX SOUTH PLAINS...AS IT BECOMES ORIENTED PARALLEL TO SWLY
   FLOW ALOFT.  THE WRN KY...NRN AR AND OK PORTIONS OF THIS BOUNDARY
   MAY RETREAT A LITTLE NWD AS A WARM FRONT SATURDAY NIGHT AS LOW LEVEL
   WINDS BACK TO SLY AND STRENGTHEN.  MEANWHILE...ANOTHER WIND SHIFT
   ATTENDANT TO THE SECOND WEAKER NRN STREAM IMPULSE WILL PROGRESS EWD
   FROM THE UPPER MS AND LOWER MO VALLEYS...BUT SHOULD WEAKEN AS IT
   MOVES INTO THE GREAT LAKES/MIDWEST TO SRN KS.
   
   ...WRN KY/TN SWWD INTO CENTRAL TX...
   AT 12Z SATURDAY...TSTMS ARE EXPECTED TO BE ONGOING INVOF THE COLD
   FRONT FROM THE OH VALLEY WSWWD THROUGH THE OZARKS TO PARTS OF
   CENTRAL OK.  A SOMEWHAT NARROW CORRIDOR OF SURFACE DEWPOINTS IN THE
   60S WILL EXTEND ALONG AND S OF THIS BOUNDARY THROUGH THE FORECAST
   PERIOD.  THE LIMITED SPATIAL EXTENT OF THIS MOISTURE CONTINUES TO
   RESULT IN A RATHER CONFINED SLIGHT RISK AREA.  HOWEVER...GIVEN SOME
   MODEL SPREAD IN THE PLACEMENT OF THE QUASI-STATIONARY BOUNDARY
   ACROSS THIS REGION AND MODELS SHOWING SUFFICIENT INSTABILITY/
   SHEAR...THE SLIGHT RISK HAS BEEN EXPANDED A LITTLE NWD AND EWD INTO
   MORE OF ERN OK...SRN MO AND THE REST OF WRN KY.  THE LACK OF HEIGHT
   FALLS AND ANY DISCERNIBLE UPSTREAM IMPULSES LIMITS CONFIDENCE IN ANY
   ONE FOCUS AREA FOR HIGHER PROBABILITIES ALONG THE FRONT.  SURFACE
   HEATING ALONG AND S OF ONGOING STORMS COMBINED WITH THE MOISTURE AND
   STEEP LAPSE RATES WILL SUPPORT MLCAPE 1000-1500 J/KG ACROSS WRN KY
   TO 2000-3000 J/KG OVER SRN OK TO CENTRAL TX.  DESPITE LACK OF
   STRONGER FORCING ALOFT...LOW LEVEL WAA IS EXPECTED TO MAINTAIN
   LIKELIHOOD FOR NEW TSTM DEVELOPMENT THROUGH THE DAY INVOF AND S OF
   THE FRONT.  EFFECTIVE BULK SHEAR 35-45 KT WILL SUPPORT ORGANIZED
   STORMS INCLUDING SUPERCELLS AND LINE SEGMENTS.  HIGHER PROBABILITIES
   ARE NOT WARRANTED AT THIS TIME...SINCE STORMS WILL LIKELY TRAIN NEWD
   AND TEND TO LIMIT THE OVERALL SEVERE WEATHER COVERAGE.  TSTMS ARE
   EXPECTED TO CONTINUE INTO SATURDAY NIGHT...MAINLY N OF THE
   FRONT...WITH SOME POTENTIAL FOR AN ISOLATED HAIL THREAT.
   
   ...MID-ATLANTIC/DELMARVA WSWWD TO MID OH VALLEY...
   SLY LOW LEVEL FLOW DEVELOPING IN LEE OF THE APPALACHIANS WILL
   SUPPORT MOISTURE RETURN WITH LOWER 60S SURFACE DEWPOINTS REACHING
   SERN PA/NJ...WHILE SWLY LOW LEVEL WINDS ACROSS THE OH VALLEY ADVECT
   SIMILAR VALUES INTO THIS REGION.  7 C/KM MIDLEVEL LAPSE RATES WILL
   EXTEND EWD ACROSS THE LOW LEVEL MOISTURE.  LIMITED SURFACE HEATING
   SHOULD ONLY RESULT IN MARGINAL INSTABILITY...THOUGH POCKET OF
   STRONGER HEATING COULD SUPPORT MLCAPE CLOSE TO 1000 J/KG.  GRADUAL
   HEIGHT RISES ACROSS THESE STATES ARE EXPECTED TO LIMIT FORCING FOR
   ASCENT ACROSS THIS REGION.  HOWEVER...MODELS SUGGEST WEAK MIDLEVEL
   IMPULSES MAY MOVE ACROSS AREAS IN LEE OF THE APPALACHIANS AND OVER
   THE OH VALLEY  DURING PEAK HEATING AIDING IN UPDRAFT DEVELOPMENT
   ALONG AND AHEAD OF THE COLD FRONT.  DEEP UNI-DIRECTIONAL WSWLY
   TROPOSPHERIC FLOW AND EFFECTIVE BULK SHEAR 40-55 KT SUGGESTS
   POTENTIAL FOR ORGANIZED STORMS WITH LINE SEGMENTS AND SUPERCELLS
   POSSIBLE.  AT THIS TIME...THE MARGINAL INSTABILITY AND WEAK FORCING
   ALOFT PRECLUDES THE INCLUSION OF A SLIGHT RISK FOR PARTS OF THIS
   REGION...BUT HIGHER PROBABILITIES MAY BE NEED IN LATER OUTLOOKS IF
   GREATER INSTABILITY IS FORECAST.
   
   ..PETERS.. 04/22/2011
   
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