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    Day 2 Outlook >
Sep 30, 2014 2000 UTC Day 1 Convective Outlook
Updated: Tue Sep 30 19:46:44 UTC 2014 (Print Version | 20140930 2000Z Day 1 shapefile | 20140930 2000Z Day 1 KML)
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 Forecast Discussion
   SPC AC 301946

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0246 PM CDT TUE SEP 30 2014

   VALID 302000Z - 011200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
   PLAINS...

   ...SUMMARY...
   ISOLATED SEVERE THUNDERSTORMS CAPABLE OF HAIL AND LOCALLY STRONG
   WIND GUSTS WILL BE POSSIBLE ACROSS PARTS OF THE GREAT PLAINS THIS
   AFTERNOON AND EVENING. THE GREATEST RISK FOR A COUPLE OF TORNADOES
   WILL BE ACROSS EASTERN SOUTH DAKOTA INTO SOUTH-CENTRAL NORTH DAKOTA.
   ELSEWHERE...A FEW STORMS WITH HAIL MAY OCCUR THIS AFTERNOON OVER
   PENNSYLVANIA AND ADJACENT STATES.

   NO CHANGES ARE MADE TO THE OUTLOOK FOR THIS ISSUANCE.

   ..BROYLES.. 09/30/2014

   .PREV DISCUSSION... /ISSUED 1130 AM CDT TUE SEP 30 2014/

   ...SYNOPSIS...

   A BRIEFLY CLOSED MID TO UPPER-LEVEL LOW OVER WRN SD WILL EVOLVE BACK
   INTO A NEGATIVELY TILTED WAVE WHILE EJECTING NNEWD INTO S-CNTRL
   CANADA IN RESPONSE TO THE AMPLIFICATION OF AN UPSTREAM SHORT-WAVE
   TROUGH OVER THE INTERIOR WEST. BETWEEN THESE TWO SYSTEMS...ONE OR
   MORE WEAK VORTICITY MAXIMA WILL PROGRESS FROM THE CNTRL ROCKIES INTO
   CNTRL PLAINS WITHIN THE BASE OF THE LONG-WAVE TROUGH PRESENT OVER
   THE INTERIOR WEST THROUGH GREAT PLAINS.

   AT THE SURFACE...AN OCCLUDED CYCLONE OVER WRN SD WILL GRADUALLY FILL
   WHILE DEVELOPING NNEWD THROUGH CNTRL ND...IN TANDEM WITH THE UPPER
   SYSTEM. AN ASSOCIATED OCCLUDED/WARM FRONT WILL CONCURRENTLY SHIFT
   NWD THROUGH THE ERN DAKOTAS AND WRN MN WHILE A PACIFIC FRONT/DRYLINE
   STALLS FROM ERN SD THROUGH CNTRL NEB...WRN KS INTO THE OK/TX PNHDLS.
   ELSEWHERE...A WEAK COLD FRONT OVER THE UPPER OH VALLEY INTO LOWER
   GREAT LAKES WILL SETTLE SLOWLY SEWD INTO THE CNTRL APPALACHIANS/MID
   ATLANTIC REGION.

   ...S-CNTRL ND INTO ERN SD THIS AFTERNOON/EVENING...

   VISIBLE SATELLITE IMAGERY SUGGESTS THAT A CORRIDOR OF STRONGER
   HEATING SHOULD OCCUR WITHIN THE MID-LEVEL DRY SLOT WRAPPING
   CYCLONICALLY THROUGH THE ERN SEMI-CIRCLE OF THE UPPER SYSTEM. WHEN
   COUPLED WITH BOUNDARY-LAYER DEWPOINTS IN THE 50S...EXPECT AT LEAST
   WEAK DESTABILIZATION /MLCAPE OF AROUND 500 J PER KG/ TO OCCUR ALONG
   THE NWD-MIGRATING SURFACE OCCLUDED/WARM FRONT. THIS SHOULD FOSTER
   THE DEVELOPMENT OF A NARROW CONVECTIVE BAND BY AFTERNOON AMIDST A
   KINEMATIC ENVIRONMENT FEATURING PRONOUNCED VEERING OF WINDS WITH
   HEIGHT WITH EFFECTIVE SRH VALUES INCREASING TO 150-250+ M2/S2. AS
   SUCH...A FEW LOW-TOPPED SUPERCELLS ARE POSSIBLE WITH A RISK FOR A
   COUPLE TORNADOES AND PERHAPS SOME MARGINALLY SEVERE HAIL.

   ...ERN NEB/WRN IA TO ERN OK/TX PNHDLS AND WRN OK...

   CONSIDERABLE EARLY-DAY CLOUDINESS /INCLUDING A FEW TSTMS/ IS PRESENT
   WITHIN THE WARM-CONVEYOR AIR STREAM FROM CNTRL KS TO ERN NEB/WRN IA
   WHICH WILL LIKELY SLOW THE DESTABILIZATION PROCESS IN THOSE AREAS.
   HOWEVER...WHERE STRONGER HEATING CAN OCCUR...THE PRESENCE OF
   BOUNDARY-LAYER DEWPOINTS IN THE MID TO UPPER 50S AND MODESTLY STEEP
   MID-LEVEL LAPSE RATES WILL YIELD AFTERNOON MLCAPE APPROACHING
   1000-1500 J/KG. 

   AS MENTIONED IN THE SYNOPSIS...WEAK VORTICITY MAXIMA EMERGING FROM
   THE CNTRL ROCKIES WILL OVERSPREAD THE REGION LATER TODAY...WHICH IN
   CONCERT WITH LOW-LEVEL CONVERGENCE ALONG THE DRYLINE/PACIFIC FRONT
   AND/OR OUTFLOW BOUNDARIES FROM EARLY-DAY TSTMS SHOULD FOCUS ISOLATED
   TO WIDELY SCATTERED AFTERNOON STORM DEVELOPMENT. WEAK MID-LEVEL
   LAPSE RATES AND THE ABOVE-MENTIONED CLOUDS ARE EXPECTED TO TEMPER
   UPDRAFT VIGOR AND THE POTENTIAL FOR AN ORGANIZED SEVERE WEATHER
   EPISODE. NONETHELESS...A FEW SEVERE STORMS /INCLUDING MARGINAL
   SUPERCELL STRUCTURES/ ARE POSSIBLE WITH THE PRIMARY HAZARDS BEING
   HAIL AND LOCALLY STRONG WIND GUSTS.

   ...LOWER GREAT LAKES/CNTRL APPALACHIANS THIS AFTERNOON...

   A MID TO UPPER-LEVEL LOW OVER THE UPPER OH VALLEY/LOWER GREAT LAKES
   WILL PROGRESS ESEWD WITH THE ASSOCIATED COLD POOL ALOFT
   OVERSPREADING A PRE-FRONTAL AIR MASS WHICH SHOULD EXPERIENCE
   ABUNDANT SUNSHINE AND THE DEVELOPMENT OF AT LEAST MODEST INSTABILITY
   BY AFTERNOON. WHILE THE STRONGEST DEEP-LAYER SHEAR ASSOCIATED WITH A
   40-50 KT MID-LEVEL JET STREAK ROUNDING THE BASE OF THE TROUGH WILL
   REMAIN DISPLACED TO THE SOUTH OF THE GREATER DESTABILIZATION...THE
   STEEPENING LAPSE RATES MAY SUPPORT SOME HAIL WITH THE STRONGEST
   STORMS.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z

        
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