SPC AC 251729

   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1229 PM CDT THU JUN 25 2015

   VALID 261200Z - 271200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF
   CENTRAL/EASTERN OKLAHOMA TO THE OHIO VALLEY REGION...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PORTIONS OF THE
   MID-ATLANTIC AND SOUTHEAST UNITED STATES WESTWARD TO SOUTHEAST
   ARIZONA...

   ...SUMMARY...
   STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE ON FRIDAY FROM
   PORTIONS OF CENTRAL AND EASTERN OKLAHOMA TO THE OHIO VALLEY REGION.

   ...SYNOPSIS...
   WATER VAPOR LOOPS INDICATE A MID-LEVEL CYCLONIC PERTURBATION
   ADVANCING SEWD OVER S-CNTRL CANADA...AS OF MID-DAY D1/THU. THIS
   FEATURE IS FORECAST TO DIG SEWD TOWARD THE UPPER MIDWEST AND GREAT
   LAKES REGION INTO D2/FRI...AND INTERACT WITH A CONVECTIVELY
   AUGMENTED LOW-LEVEL FRONTAL ZONE EXTENDING FROM THE CNTRL PLAINS TO
   THE GREAT LAKES REGION. IN RESPONSE TO THESE DEVELOPMENTS...SFC LOW
   PRESSURE WILL DEVELOP EWD ALONG THE FRONTAL ZONE FROM ERN PARTS OF
   THE CNTRL PLAINS TO THE MIDDLE OHIO VALLEY THROUGH THE D2/FRI
   PERIOD. AS THE LARGER-SCALE CYCLONIC PERTURBATION
   BROADENS/AMPLIFIES...THE SFC LOW WILL DEEPEN. A COLD FRONT TRAILING
   WSW OF THE LOW WILL PROGRESS SWD ACROSS PARTS OF THE CNTRL/S-CNTRL
   CONUS...WHILE A WARM/QUASI-STATIONARY FRONT BRANCHES E OF THE LOW
   TOWARD THE ATLANTIC COAST.

   ...PORTIONS OF CENTRAL/EASTERN OKLAHOMA TO THE OHIO VALLEY REGION...

   CONVECTION WILL LIKELY BE ONGOING AT THE START OF THE PERIOD FROM
   PARTS OF THE CNTRL PLAINS TO THE OHIO VALLEY IN PROXIMITY TO THE
   FRONTAL ZONE. RELATED OUTFLOW WILL SUBSTANTIALLY MODULATE THE
   POSITION OF THE EFFECTIVE SFC BOUNDARY. UNCERTAINTY IN EVENTUAL
   MESO-ALPHA/BETA SCALE EVOLUTION OF LATE-D1/THU CONVECTION EXTENDS TO
   THE POSITION OF THIS BOUNDARY FOR D2/FRI...LIMITING OVERALL
   CONFIDENCE IN THE EVOLUTION OF D2/FRI CONVECTION. REGARDLESS...RICH
   BOUNDARY-LAYER MOISTURE CHARACTERIZED BY SFC DEWPOINTS IN THE LOWER
   70S WILL FACILITATE MODERATE TO STRONG DIURNAL DESTABILIZATION S OF
   THE EFFECTIVE FRONT. TSTMS WILL LIKELY INTENSIFY AND/OR DEVELOP WITH
   DIURNAL HEATING ACROSS THE SLIGHT-RISK AREA. MULTICELL CLUSTERS WILL
   LIKELY EVOLVE FROM THIS ACTIVITY THROUGH THE AFTERNOON INTO THE
   EVENING...WITH SVR WIND/HAIL POSSIBLE.

   THE GREATEST SVR POTENTIAL MAY EXIST ACROSS PARTS OF E-CNTRL/SERN OK
   INTO NW/W-CNTRL AR...WHERE COLD-POOL AMALGAMATION STEMMING FROM
   CONVECTION EVOLVING ALONG THE SYNOPTIC FRONT MAY LOCALLY ENHANCE THE
   SVR-WIND POTENTIAL. HIGHER CONFIDENCE IN FRONTAL INTERCEPTION OF
   STRONGER BUOYANCY EXISTS IN THESE AREAS OWING TO THE ANTICIPATION
   THAT ANTECEDENT CONVECTION/CONVECTIVE DEBRIS WILL REMAIN TO THE N.
   UPGRADE TO ENH DESIGNATION MAY BE NECESSARY IN SUBSEQUENT OUTLOOKS.
   HOWEVER...WITHOUT STRONGER DEEP SHEAR AND WITHOUT STEEPER MID-LEVEL
   LAPSE RATES...OVERALL CONFIDENCE IN A MORE SUBSTANTIAL SVR RISK IS
   LIMITED AT THIS TIME. 

   DEEP SHEAR WILL BE STRONGEST ACROSS PARTS OF THE OHIO
   VALLEY...PARTICULARLY NEAR/E OF THE SFC LOW -- I.E. INVOF THE
   WARM/QUASI-STATIONARY FRONT. THIS MAY BE THE FOCUS FOR SOMEWHAT
   GREATER SVR-TSTM POTENTIAL AND PERHAPS A NON-ZERO TORNADO
   RISK...ESPECIALLY WHERE SFC WINDS REMAIN SOMEWHAT BACKED/ELY AMIDST
   MODEST BUOYANCY. SUCH POTENTIAL COULD BE ENHANCED BY THE PROPENSITY
   FOR LOW-LEVEL POLEWARD MASS FLUXES E OF THE SFC CYCLONE TO ENCOURAGE
   NWD EXTENSION OF HIGHER THETA-E AIR INTO THE ZONE OF STRONGER DEEP
   SHEAR. HOWEVER...THE POSITION OF THE EFFECTIVE FRONT WILL PLAY A
   SUBSTANTIAL ROLE IN THE DELINEATION OF GREATER SVR-TSTM RISK...FOR
   WHICH TOO MUCH UNCERTAINTY EXISTS FOR THE INCLUSION OF HIGHER
   SVR-TSTM PROBABILITIES.

   ...PORTIONS OF THE MID-ATLANTIC AND SOUTHEAST UNITED STATES WESTWARD
   TO SOUTHEAST ARIZONA...

   A BROAD REGION OF MARGINAL SVR-TSTM POTENTIAL ENCOMPASSES FOUR
   GENERAL REGIMES THAT SURROUND THE SLIGHT-RISK AREA:
   /1/ CLUSTERS OF DIURNALLY INTENSIFYING CONVECTION IN PROXIMITY TO/S
   OF THE QUASI-STATIONARY/WARM SFC FRONT ACROSS PARTS OF THE
   MID-ATLANTIC...
   /2/ SCATTERED DIURNALLY ENHANCED CONVECTION IN THE
   UNCAPPED...HIGH-PW AIR ACROSS PARTS OF THE SERN STATES/LOWER MS
   VALLEY TO THE TN VALLEY/SRN APPALACHIANS...
   /3/ TSTM ACTIVITY DEVELOPING NEAR THE FRONT ACROSS THE SRN HIGH
   PLAINS AMIDST ELY/UPSLOPE FLOW...AND
   /4/ MONSOON-RELATED CONVECTION ACROSS PARTS OF SERN AZ/SWRN NM.

   IN EACH CASE...SOME RISK FOR LOCALLY DMGG WIND GUSTS WILL EXIST.
   LARGE DCAPE SHOULD SUPPORT SUCH POTENTIAL IN THE SWRN CONUS...WHILE
   WATER LOADING ASSOCIATED WITH HIGH PW ENCOURAGES SUCH POTENTIAL
   ELSEWHERE. HOWEVER...THE LACK OF STRONGER DEEP SHEAR AND/OR LACK OF
   STRONGER DEEP ASCENT IN THESE AREAS LIMIT OVERALL CONFIDENCE IN MORE
   ORGANIZED/SUSTAINED CONVECTION...PRECLUDING ADDITIONAL SLIGHT-RISK
   DESIGNATION AT THIS TIME.

   ..COHEN.. 06/25/2015

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