SPC AC 261315

   DAY 1 CONVECTIVE OUTLOOK CORR 1
   NWS STORM PREDICTION CENTER NORMAN OK
   0815 AM CDT MON MAY 26 2014

   VALID 261300Z - 271200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS TX AND SWRN OK...

   CORRECTED FOR HAIL LINE

   ...SUMMARY...
   SEVERE THUNDERSTORMS WILL BE POSSIBLE ACROSS A LARGE PORTION OF WEST
   AND SOUTHWEST TEXAS INTO SOUTHWESTERN OKLAHOMA...MAINLY DURING THE
   AFTERNOON AND EVENING.  ELSEWHERE...STRONG TO MARGINALLY SEVERE
   STORMS WILL BE POSSIBLE ACROSS PARTS OF THE NORTHERN HIGH
   PLAINS...UPPER MIDWEST...AND NEW ENGLAND.

   ...SYNOPSIS...
   IN MIDDLE-UPPER LEVELS...PRIMARY INFLUENCE ON SVR POTENTIAL THIS
   PERIOD WILL BE PERSISTENT/SLOW-MOVING CYCLONE -- CENTERED AT 12Z
   OVER NWRN NM.  PRIOR/00Z 500-MB ISALLOHYPSIC ANALYSIS SHOWED LACK OF
   HEIGHT FALLS AND INCREASING AREAL COVERAGE OF RISES IN ALL QUADRANTS
   OF THIS CYCLONE...INDICATING THAT THE FILLING PROCESS HAS BEGUN. 
   500-MB LOW IS EXPECTED TO CONTINUE WEAKENING AS IT ACCELERATES ESEWD
   TO CDS/LTS REGION BY 12Z.  IN AFFECTED FLOW FIELDS ALOFT...MCV NOW
   EVIDENT IN REFLECTIVITY FIELDS AND STLT IMAGERY OVER
   CENTRAL/N-CENTRAL TX SHOULD EJECT NEWD TO SERN MO/SERN KS
   REGION...SIMILARLY TO RR FCST.  THIS FEATURE ALSO IS DEPICTED BY
   26/06Z NAM...BUT THAT MODEL ODDLY SPLITS/DISPLACES MUCH OF ITS
   VORTICITY FIELD STRONGLY RIGHTWARD OF WINDS ALOFT.

   ELSEWHERE...MIDDLE-UPPER-LEVEL CYCLONE OVER QUE SHOULD TRACK SEWD
   ACROSS WRN MARITIME PROVINCES.  SHORTWAVE TROUGH NOW APCHG WA COAST
   WILL MOVE NEWD ACROSS WA TODAY...THEN PHASE WITH ANOTHER WEAK
   PERTURBATION TONIGHT TO FORM BROAD/WEAK CLOSED CYCLONE OVER  NRN
   POTIONS AB/SK.

   AT SFC...11Z ANALYSIS SHOWED COLD FRONT FROM FAR NRN ONTARIO SWWD
   ACROSS NERN MN TO WEAK LOW OVER CENTRAL SD...THEN NWWD OVER ERN MT
   TO ANOTHER WEAK LOW ALONG MT/SK BORDER.  COLD FRONTOGENESIS WAS
   EVIDENT SW OF LATTER LOW ACROSS CENTRAL/SWRN MT.  FRONT SHOULD MOVE
   SLOWLY EWD ACROSS MOST OF MT THROUGH PERIOD. AND SEWD ACROSS
   PORTIONS WI...MN...NRN IA AND NERN NEB.  FARTHER S...SEVERAL OUTFLOW
   BOUNDARIES WERE EVIDENT OVER TX/OK FROM BOTH ONGOING AND PRIOR
   CONVECTION DATING BACK TO YESTERDAY AFTN.  DRYLINE WAS ANALYZED FROM
   WEAK LOW OVER SERN CO SSWWD ACROSS ERN NM THEN SSEWD OVER BIG BEND
   REGION OF W TX.  MIXING MIGHT MOVE DRYLINE SLIGHTLY EWD TODAY...BUT
   ALSO WILL ACT TO SHARPEN ITS DEFINITION.

   ...SRN PLAINS...
   SCATTERED TO LOCALLY NUMEROUS TSTMS ARE EXPECTED THIS
   AFTN...INITIALLY IN DISCRETE TO SMALL-CLUSTER MODES OF MULTICELLS
   AND SUPERCELLS.  ACTIVITY MAY PRODUCE LARGE HAIL AND DAMAGING GUSTS.
   MAIN POTENTIAL GENESIS ZONES APPEAR TO BE DRYLINE AND OUTFLOW
   BOUNDARIES FROM CONVECTION NOW OVER SERN PANHANDLE AND NW TX NEAR
   CAPROCK.  THIS BOUNDARY REMAINS PROGRESSIVE...AND THERE IS SOME
   UNCERTAINTY WHERE IT WILL SETTLE DEPENDING ON
   1. DEPTH OF DENSITY CURRENT...WHICH IS DIFFICULT TO ASCERTAIN GIVEN
   ITS LOCATION IN UPPER-AIR DATA VOID...AND
   2.  DURATION/REDEVELOPMENT OF ELEVATED CONVECTION TO ITS N THAT
   WOULD DEEPEN AND REINFORCE ASSOCIATED DENSITY CURRENT.

   CHARACTER AND ULTIMATE STALLING/RETREAT POSITION OF THAT BOUNDARY
   WILL PLAY SUBSTANTIAL ROLE IN DEVELOPMENT AND MAINTENANCE OF
   CONVECTION LATER TODAY...INCLUDING CONDITIONAL TORNADO POTENTIAL FOR
   ANY SUSTAINED/DISCRETE SUPERCELLS.  ACTIVITY SHOULD AGGREGATE INTO
   ONE OR TWO PRIMARY COMPLEXES LATE AFTN INTO TONIGHT...MOVING EWD
   ACROSS OUTLOOK AREA.  SFC DEW POINTS ARE SOMEWHAT LOWER THAN
   PREVIOUS DAYS OVER MOST OF THIS AREA THANKS TO ANTECEDENT CONVECTIVE
   PROCESSES...HOWEVER SFC HEATING AND AVAILABLE MOISTURE SHOULD
   SUPPORT 1000-2000 J/KG PEAK MLCAPE IN AIR MASS THAT IS PRECONVECTIVE
   WITH RESPECT TO CURRENT/AFTN ACTIVITY.  DEEP SHEAR WILL BE SOMEWHAT
   LESS THAN BEFORE ALSO...DUE TO WEAKENING OF MID-UPPER-LEVEL
   CYCLONE...BUT STILL ADEQUATE FOR AT LEAST INTERMITTENT SUPERCELLS.

   FARTHER S...QUASI-LINEAR MCS NOW INVOF DRT-JCT LINE INITIALLY
   APPEARS ELEVATED BEHIND EARLIER OUTFLOW BOUNDARY...BUT MAY BECOME
   SFC-BASED WITH INCREASING WIND RISK AS IT MOVES EWD INTO
   PROGRESSIVELY HIGHER-THETAE/DIABATICALLY HEATED AIR MASS NEXT FEW
   HOURS.

   ...TX COASTAL PLAIN...
   SMALL CONVECTIVE COMPLEX OF TSTMS IS MOVING EWD OVER MIDDLE TX
   COASTAL PLAIN.  SRN PORTION OF THIS CONVECTION HAS EXHIBITED
   OCNL/MESSY SUPERCELL STRUCTURES WITH EPISODIC INTENSIFICATION OF
   WIND/HAIL POTENTIAL.  THIS ACTIVITY IS MOVING EWD ALONG SUBTLE
   THETAE GRADIENT...S OF WHICH SFC DEW POINTS MID-70S F SUPPORT
   POTENTIAL FOR 1500-2000 J/KG MLCAPE BY LATE MORNING.  BY
   CONTRAST...LOW-LEVEL CONVERGENCE SHOULD WEAKEN WITH TIME AND EWD
   EXTENT.  GIVEN THESE MIXED SIGNALS...MRGL SVR PROBABILITIES HAVE
   BEEN EXTENDED EWD.  ADDITIONAL TSTMS MAY DEVELOP ALONG RESULTANT
   OUTFLOW BOUNDARY FROM THIS AREA WSWWD ACROSS S-CENTRAL TX
   TODAY...OFFERING RISK OF ISOLATED LARGE HAIL AND STG/DAMAGING GUSTS.

   ...NEW ENGLAND...
   WIDELY SCATTERED TSTMS SHOULD FORM AGAIN TODAY AS POCKETS OF
   SUSTAINED DIABATIC SFC HEATING DECREASE BOUNDARY-LAYER CINH...IN
   PRESENCE OF ADEQUATE LOW-LEVEL MOISTURE.  SOME CONVECTION MAY OFFER
   SVR HAIL.  THIS PROCESS SHOULD BE SLOWER AND SOMEWHAT MORE MUTED
   TODAY THAN YESTERDAY...GIVEN
   1. CLOUD COVER HERE AND UPSTREAM IN VIS/IR IMAGERY...RESTRICTING
   COVERAGE/PACE OF DIABATIC SFC HEATING...AND
   2. MRGL LAPSE RATES ALOFT.
   STILL...AFOREMENTIONED PASSAGE OF UPPER CYCLONE ACROSS MARITIMES
   WILL TIGHTEN HEIGHT GRADIENT AND ENHANCE DEEP SHEAR...AMIDST 200-600
   J/KG MLCAPE.  HAIL POTENTIAL WILL DIMINISH GREATLY AFTER DARK AS
   BOUNDARY LAYER STABILIZES AND REDUCES ALREADY WEAK CAPE.

   ...CENTRAL PLAINS TO WI...
   SCATTERED TSTMS SHOULD DEVELOP THIS AFTN NEAR SFC COLD FRONT...WITH
   ISOLATED TO WIDELY SCATTERED WARM-SECTOR CONVECTION ALSO POSSIBLE IN
   WEAKLY CAPPED ENVIRONMENT.  A FEW CELLS MAY PRODUCE HAIL/GUSTS NEAR
   SVR LEVELS.  SFC DIABATIC HEATING WILL FOSTER WELL-MIXED SUBCLOUD
   LAYER...BUT WEAK LAPSE RATES ALOFT SHOULD LIMIT MLCAPE TO 500-1500
   J/KG RANGE.  STRONGLY DIFLUENT AND RELATIVELY WEAK FLOW ALOFT IS
   FCST OVER MOST OF THIS AREA...INVOF SHORTWAVE RIDGE.  THIS WILL
   LIMIT DEEP SHEAR AND...BY EXTENSION...POTENTIAL FOR MORE THAN
   BRIEFLY/MRGLLY SVR ORGANIZATION OF CONVECTION.

   ...NRN PLAINS/NRN ROCKIES...
   WIDELY SCATTERED TSTMS SHOULD DEVELOP TODAY INVOF SFC COLD FRONT
   OVER MT...SOME OF WHICH MAY REACH WRN ND BEFORE DISSIPATING THIS
   EVENING.  ADDITIONAL CONVECTION SHOULD DEVELOP OVER HIGHER TERRAIN
   OF SRN MT...ALSO MOVING GENERALLY EWD TO ENEWD.  STEEP
   LOW-MIDDLE-LEVEL LAPSE RATES...STG DIABATIC SFC HEATING...AND 40S TO
   LOW-50S F SFC DEW POINTS WILL SUPPORT CORRIDOR OF 500-800 J/KG
   MLCAPE CORRESPONDING APPROXIMATELY TO 5% SVR-PROBABILITY AREA. 
   ISOLATED STG/DAMAGING GUSTS AND HAIL NEAR SVR LEVELS ARE POSSIBLE.

   ..EDWARDS/MARSH.. 05/26/2014

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