SPC AC 141253

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0753 AM CDT MON JUL 14 2014

   VALID 141300Z - 151200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS MID-SOUTH REGION TO
   ERN IL AND NERN CONUS...

   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NRN ROCKIES FROM
   YELLOWSTONE AREA TO ID PANHANDLE AND WRN MT...

   ...SUMMARY...
   SCATTERED SEVERE STORMS WITH MAINLY A WIND THREAT WILL BE POSSIBLE
   DURING THE DAY FROM THE MID-SOUTH REGION ACROSS THE OHIO VALLEY AND
   INTO SOUTHERN NEW ENGLAND.  SEVERE GUSTS AND HAIL ALSO ARE EXPECTED
   FROM SOME THUNDERSTORMS THIS AFTERNOON OVER THE NORTHERN ROCKIES.

   --- TECHNICAL DISCUSSION ---

   ...SYNOPSIS...
   IN MID-UPPER LEVELS...CONUS PORTION OF LONGWAVE PATTERN WILL REMAIN
   DOMINATED BY WRN MEAN RIDGING AND TROUGHING OVER GREAT LAKES REGION.
   LATTER WILL AMPLIFY THROUGH PERIOD AS STG SHORTWAVE WITH
   SMALL/EMBEDDED 500-MB LOW -- NOW OVER NRN MN -- PIVOTS SEWD OVER
   UPPER MS VALLEY AND LM...REACHING LOWER MI BY 12Z.  HEIGHTS WILL
   FALL OVER BROAD SWATH OF MS VALLEY...TN VALLEY REGION...AND
   CENTRAL/SRN APPALACHIANS AHEAD OF THIS PERTURBATION. 
   MEANWHILE...WELL-DEFINED SHORTWAVE TROUGH -- NOW APPARENT IN
   MOISTURE-CHANNEL IMAGERY OVER INTERIOR WA/ORE -- WILL MOVE THROUGH
   MEAN-RIDGE POSITION BETWEEN 00-06Z AND REACH WRN MT/SERN ID BY END
   OF PERIOD.  OVER SWRN CONUS...ELY SHORTWAVE TROUGH NOW OVER COASTAL
   SRN CA AND NRN BAJA WILL PROGRESS OFFSHORE OVER PAC...ALTHOUGH
   MINOR/CONVECTIVELY GENERATED VORTICITY LOBES STILL MAY AFFECT PARTS
   OF SRN AZ.

   AT SFC...WAVY/QUASISTATIONARY BAROCLINIC ZONE -- NOW COMPOSED ALMOST
   ENTIRELY OF CONVECTIVE OUTFLOWS OF VARYING AGES -- WAS EVIDENT IN
   11Z ANALYSIS FROM NRN/WRN NY ACROSS WV AND WRN KY...EXTREME NRN
   AR...NERN THROUGH SWRN OK AND SRN TX PANHANDLE.  THIS BOUNDARY
   SHOULD REMAIN NEARLY STATIONARY EXCEPT WHERE ALTERED BY ADDITIONAL
   CONVECTION...AND LATE IN PERIOD...OVERTAKEN IN SRN PLAINS AND
   MID-SOUTH REGION BY SFC COLD FRONT. COLD FRONT WAS DRAWN AT 11Z FROM
   WEAK LOW OVER LOWER MI WSWWD ACROSS SRN IA...ERN NEB...SWRN SD AND
   CENTRAL MT.  BY 00Z...FRONT SHOULD REACH SRN IL...NRN OK AND NRN TX
   PANHANDLE.  BY 12Z...FRONT SHOULD REACH ERN OH...ERN TN...SRN
   AR...NW TX AND NERN NM.

   ...MID-SOUTH REGION TO SRN LOWER MI AND NERN CONUS...
   COMPLEX CONVECTIVE SCENARIO IS EVIDENT ACROSS THIS REGION WITH
   CONSIDERABLE SPATIAL OVERLAP BETWEEN ASSORTED AREAS OF MESOSCALE
   POTENTIAL.  EXPECT GRADUAL INCREASE IN TSTM COVERAGE/INTENSITY FROM
   LATE MORNING THROUGH AFTN ALONG STALLED FRONTAL/OUTFLOW ZONE AS WELL
   AS ANY OTHER OUTFLOW BOUNDARIES AND DIFFERENTIAL-HEATING ZONES
   WITHIN THIS CORRIDOR.  RICHEST LOW-LEVEL MOISTURE WILL BE NEAR AND S
   OF QUASISTATIONARY BAROCLINIC ZONE...WHICH ALSO WILL REMAIN
   POSITIONED S OF MOST FAVORABLE DEEP SHEAR.  HOWEVER...MULTICELLULAR
   TSTM COVERAGE SHOULD GROW SUFFICIENTLY DENSE AMIDST MRGL SHEAR TO
   WARRANT 15% WIND THREAT.

   ADDITIONALLY...SYNOPTIC COLD FRONT SHOULD CONTRIBUTE TO TSTM
   GENERATION OVER PORTIONS IL/INDIANA THIS AFTN...AMIDST STRENGTHENING
   DEEP SHEAR AND LARGE-SCALE ASCENT RELATED TO APCHG STG
   MID-UPPER-LEVEL TROUGH.  LOW-LEVEL WIND PROFILES AHEAD OF FRONT WILL
   BE LARGELY UNIDIRECTIONAL...BUT AMIDST INTENSIFYING MIDLEVEL WINDS. 
   AS SUCH...PRIND DAMAGING GUSTS WILL BE PRIMARY CONCERN...WITH
   ISOLATED SVR HAIL ALSO POSSIBLE.

   ...NRN ROCKIES...
   WIDELY SCATTERED TO SCATTERED TSTMS ARE FCST THIS AFTN WITH
   POTENTIAL FOR SOME CONVECTION TO PRODUCE DAMAGING GUSTS AND OCNL
   LARGE HAIL.  850-500-MB LAPSE RATES AROUND 8-8.5 DEG C/KM WERE
   EVIDENT IN 12Z OTX/BOI RAOBS...AND LARGE-SCALE ASCENT PRECEDING
   MID-UPPER TROUGH SHOULD SPREAD COLDER MIDLEVEL AIR ACROSS THOSE
   AREAS TO NRN ROCKIES WITH TIME.  THIS PROCESS...IN CONJUNCTION WITH
   LOW-LEVEL CONVERGENCE NEAR S-N TROUGH...AT LEAST MRGL LOW-LEVEL
   MOISTURE...AND DIABATICALLY STEEPENED BOUNDARY-LAYER LAPSE
   RATES...WILL CONTRIBUTE TO TSTM DEVELOPMENT AND SVR POTENTIAL.  ELY
   NEAR-SFC WINDS IN FCST SOUNDINGS NEAR AND E OF LOW-LEVEL
   TROUGH...COMBINED WITH STRENGTHENING FLOW ALOFT...LEAD TO
   EFFECTIVE-SHEAR MAGNITUDES EXCEEDING 50 KT IN SOME FCST
   SOUNDINGS...AMIDST MLCAPE LOCALLY TOPPING 1000 J/KG.  GIVEN THESE
   POSSIBLE CONDITIONS THAT SUPPORT BOTH SUPERCELL AND BOWING
   STRUCTURES...SVR-WIND/HAIL PROBABILITIES ARE BEING UPGRADED TO
   CATEGORICAL SLGT-RISK THRESHOLDS.

   ...SRN PLAINS TO S-CENTRAL ROCKIES...
   WIDELY SCATTERED TO SCATTERED TSTMS ARE EXPECTED TO DEVELOP THIS
   AFTN INTO EARLY EVENING ALONG OUTFLOW/FRONTAL ZONE...AS WELL AS
   APCHG SYNOPTIC COLD FRONT...AND WITHIN FAVORABLY MOIST AIR MASS IN
   BETWEEN.  STG SFC HEATING BENEATH FAVORABLE LAPSE RATES ALOFT WILL
   CONTRIBUTE TO PEAK MLCAPES IN 2000-2500 J/KG RANGE OVER LOWER
   ELEVATIONS.  DIRECTIONAL SHEAR WILL BE STG...BUT WITH LIGHT
   LOW-MIDDLE-LEVEL FLOW...EFFECTIVE-SHEAR MAGNITUDES WILL REMAIN BELOW
   35 KT IN MOST OF THIS CORRIDOR.  ISOLATED HAIL AND GUSTS NEAR SVR
   LEVELS ARE POSSIBLE.

   ...AZ...
   WIDELY SCATTERED TO SCATTERED TSTMS MAY DEVELOP AGAIN THIS AFTN
   ALONG HIGHER TERRAIN OF SERN AZ AND INVOF MOGOLLON RIM...AMIDST
   SEASONALLY RICH LOW-LEVEL MOISTURE.  RIM MAY HAVE RELATIVELY DENSE
   CONCENTRATION OF CONVECTION TODAY...GIVEN EXPECTED SFC HEATING AND
   AVAILABLE MOISTURE.  LAPSE RATES WILL BE RATHER MODEST...GIVEN
   WIDESPREAD NATURE OF CONVECTION FROM PRIOR DAY...LIMITING BUOYANCY. 
   MEANWHILE...DEEP LAYER OF ELY FLOW ALOFT WILL REMAIN...BUT SHOULD BE
   WEAK IN MOST AREAS AS PRIMARY ELY TROUGH MOVES FARTHER AWAY FROM
   THIS AREA.  STILL...A FEW CLUSTERS OF CONVECTION MAY PUSH OUTFLOW
   ACROSS LOWER/DESERT ELEVATIONS AND INTO WELL-MIXED BOUNDARY
   LAYERS...WITH GUSTS APCHG SVR LIMITS LIKELY AND ISOLATED SVR GUSTS
   POSSIBLE.

   ..EDWARDS/ROGERS.. 07/14/2014

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