May 9, 2013 0600 UTC Day 2 Convective Outlook
Updated: Thu May 9 06:06:31 UTC 2013
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20130509 0600 UTC Day 2 Outlook Graphic
Probabilistic Graphic
20130509 0600 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.
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 173,207 29,213,504 Houston, TX...San Antonio, TX...Austin, TX...Columbus, OH...Louisville, KY...
   SPC AC 090559
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1259 AM CDT THU MAY 09 2013
   
   VALID 101200Z - 111200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/S TX...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OH VALLEY TO PA...
   
   ...SYNOPSIS...
   TRANSITIONAL SPLIT-FLOW PATTERN FCST IN MID-UPPER LEVELS...WITH MORE
   PROGRESSIVE SHORTWAVE FEATURES OVER MOST OF CONUS THAN PREVIOUS
   DAYS.  NRN-STREAM SHORTWAVE TROUGH -- NOW LOCATED OVER EXTREME NWRN
   CANADA -- IS EXPECTED TO SWIVEL SEWD AND AMPLIFY
   CONSIDERABLY...REACHING SK/NRN MB BY START OF PERIOD.  SYSTEM SHOULD
   DEVELOP CLOSED 500-MB LOW OVER NRN ONT BY 11/12Z...WITH SHORTWAVE
   TROUGH SSWWD ACROSS MN.  WEAKENING CYCLONE NOW OVER MID-ATLC REGION
   IS FCST TO EJECT AWAY FROM NEW ENGLAND THIS PERIOD...OVER MARITIME
   PROVINCES OF CANADA AND ADJACENT ATLC WATERS.  MOISTURE CHANNEL
   IMAGERY AND VWP/PROFILER DATA SHOW ZONALLY ELONGATED CYCLONE FROM
   CENTRAL ROCKIES WSWWD ACROSS 4-CORNERS REGION...PHASED WITH
   SECONDARY SHORTWAVE TROUGH AND SPEED MAX NOW DIGGING SEWD ACROSS
   SERN CA.  ERN PORTION OF ROCKIES PERTURBATION SHOULD MERGE/PHASE
   WITH INITIALLY SEPARATE PERTURBATION NOW OVER FSD/SUX REGION. 
   RESULTING POSITIVELY TILTED SHORTWAVE TROUGH SHOULD MOVE ENEWD
   ACROSS MID-UPPER MS VALLEY REGION AND UPPER GREAT LAKES...WEAKENING
   AMIDST STG HEIGHT FALLS THAT WILL PRECEDE CANADIAN SHORTWAVE. 
   TRAILING PORTION OF CURRENT 4-CORNERS AREA PERTURBATION EFFECTIVELY
   SHOULD MERGE WITH SRN CA SYSTEM...RESULTING IN STG/SEWD-MOVING
   TROUGH OVER NWRN MEX.
   
   AT SFC...FRONTAL-WAVE LOW IS FCST TO PROPAGATE EWD ALONG BAROCLINIC
   ZONE...FROM MICHIANA AREA AROUND 10/12Z TO EARLY IN PERIOD ACROSS
   ADIRONDACKS REGION BY END OF PERIOD.  TRAILING COLD FRONT IS FCST TO
   MOVE SEWD TO NEAR CENTRAL IL...SRN MO...SERN OK..AND NW TX AROUND
   START OF PERIOD...LIKELY PRECEDED BY TSTM OUTFLOWS OVER SRN PLAINS. 
   ISALLOBARIC FORCING RELATED TO LOW PRESSURE DEVELOPMENT OVER NERN
   MEX SHOULD YIELD ELY FLOW COMPONENT AHEAD OF FRONT OVER MUCH OF
   CENTRAL AND S TX.  BY END OF PERIOD...FRONT SHOULD EXTEND OVER NRN
   NY...OH...KY...SRN AR AND S TX.  SEPARATE/STG COLD FRONT RELATED TO
   NRN-STREAM SHORTWAVE TROUGH SHOULD SURGE SWD/SEWD OVER NRN PLAINS.
   
   ...TX...
   PREFRONTAL REGIME OF SERIAL MCS DEVELOPMENT/PROPAGATION AND BOUNDARY
   PRODUCTION IS POSSIBLE FROM DAY-1 THROUGH THIS PERIOD.  SEE SPC
   DAY-1 OUTLOOK FOR MORE DETAILS ON INITIAL ROUND OF THIS ACTIVITY. 
   ONE OR MORE CLUSTERS OF TSTMS THEN MAY BE ONGOING NEAR BEGINNING OF
   PERIOD OVER N-CENTRAL OR CENTRAL TX...IN ENVIRONMENT CHARACTERIZED
   BY WEAKENING NOCTURNAL LLJ AND STEEP MIDLEVEL LAPSE RATES.  MRGL SVR
   HAIL IS POSSIBLE...AND CONDITIONAL THREAT EXISTS FOR DAMAGING GUSTS
   TO EXTENT ACTIVITY CAN DEVELOP/PROPAGATE ALONG ITS OWN COLD POOL.
   
   SCATTERED TO LOCALLY NUMEROUS TSTMS SHOULD DEVELOP OVER SOME PART OF
   CENTRAL/S TX DURING AFTN/EVENING...MOST PROBABLY CONCENTRATED INVOF
   FRONTAL ZONE AND OUTFLOW BOUNDARY FROM PRIOR CONVECTION. 
   CONDITIONAL POTENTIAL EXISTS ALONG DRYLINE SEGMENT OVER S
   TX...THOUGH DIURNAL COVERAGE OF DRYLINE ACTIVITY SHOULD BE LIMITED
   BY CINH RELATED TO EWD TRANSPORT OF EML AIR ALOFT FROM MEX.  MIX OF
   SUPERCELLULAR AND MULTICELLULAR STRUCTURES IS POSSIBLE EARLY IN
   CONVECTIVE CYCLE...OFFERING LARGE HAIL AND ISOLATED DAMAGING GUSTS. 
   ACTIVITY THEN MAY GROW UPSCALE INTO ROUGHLY EWD-MOVING MCS DURING
   PORTIONS EVENING/OVERNIGHT HOURS.  THOUGH WEAK FLOW IS FCST IN MOST
   OF BOUNDARY LAYER...ELY SFC WINDS SHOULD ELONGATE HODOGRAPH ENOUGH
   TO PROVIDE FAVORABLE SRH FOR POTENTIAL OF DEVIANTLY MOVING
   SUPERCELLS.  AREA WILL LIE BENEATH STG MID-UPPER FLOW ASSOCIATED
   WITH SUBTROPICAL JET...WITH 40-50 KT 500-MB FLOW AND 250-MB WINDS
   70-80 KT EXPECTED.  SPECIFIC TIMING/PLACEMENT OF GREATEST CONVECTIVE
   POTENTIAL IS STRONGLY CONDITIONAL ON BOUNDARIES LEFT BEHIND BY PRIOR
   CONVECTION.  AS SUCH...IT IS TOO SOON TO ASSIGN SPECIFIC
   SIGNIFICANT-SVR AREA...ALTHOUGH STG DEEP SHEAR AND LARGE CAPE SHOULD
   EXIST IN SUPPORT OF DAMAGING HAIL WITH ANY RELATIVELY
   SUSTAINED/DISCRETE SUPERCELLS THAT CAN DEVELOP.
   
   ...OH VALLEY...PA...
   SCATTERED TSTMS ARE EXPECTED TO DEVELOP ALONG/AHEAD OF SFC COLD
   FRONT...IN ZONE OF DIURNALLY HEATED/DESTABILIZED AIR MASS
   CHARACTERIZED BY SFC DEW POINTS RANGING FROM 60S OVER OH TO 50S IN
   NRN PA.  DAMAGING GUSTS SHOULD BE MAIN CONCERN...WITH OCNL SVR HAIL
   ALSO POSSIBLE.  MAIN BAND OF CONVECTIVE FORCING SHOULD BE ALIGNED
   NEARLY PARALLEL TO FLOW ALOFT...INDICATING DOMINANT QUASI-LINEAR
   MODE.  HOWEVER...THERE IS ENOUGH CURVATURE/SRH IN FCST HODOGRAPHS TO
   SUPPORT AT LEAST TRANSIENT SUPERCELL CHARACTERISTICS IN ANY
   SUSTAINED/DISCRETE CONVECTION.  THIS AREA WILL LIE BENEATH
   TIGHTENING HEIGHT GRADIENTS ALOFT AND STRENGTHENING DEEP
   SHEAR...PERIPHERALLY RELATED TO APCHG CANADIAN SHORTWAVE.  WEAKER
   PERTURBATION ALOFT -- EJECTING NEWD FROM MS VALLEY -- ALSO MAY
   CONTRIBUTE SUBTLE LARGE-SCALE ASCENT DURING AFTERNOON.  LIMITING
   FACTOR WILL BE WEAK LAPSE RATES ALOFT...LIKELY KEEPING MLCAPE IN
   300-800 J/KG RANGE MOST AREAS.
   
   ..EDWARDS.. 05/09/2013
   
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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z