SPC AC 280533
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1233 AM CDT THU AUG 28 2008
   
   VALID 281200Z - 291200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SRN KS TO WRN LM...
   
   ...SYNOPSIS...
   IN MID-UPPER LEVELS...PROGRESSIVE NRN STREAM PATTERN FCST TO
   CONTINUE THROUGH PERIOD. WELL-DEFINED TROUGHING -- NOW EXTENDING
   FROM UPPER LOW OVER FAR NRN MB SSWWD ACROSS CENTRAL HIGH PLAINS --
   IS EXPECTED TO SHIFT EWD ACROSS UPPER GREAT LAKES REGION.  THIS WILL
   OCCUR AS REINFORCING SHORTWAVE PERTURBATION -- NOW SUBTLY EVIDENT IN
   MOISTURE CHANNEL IMAGERY OVER MT -- DIGS ESEWD ACROSS DAKOTAS AND
   MERGES WITH VORTICITY LOBE TRAILING SWWD FROM LEAD SHORTWAVE NOW
   OVER ND.  RESULTANT/BLENDED SHORTWAVE TROUGH SHOULD MOVE EWD ACROSS
   UPPER MS VALLEY DURING DAY...THEN WEAKEN SOMEWHAT AS IT EJECTS NEWD
   ACROSS ERN UPPER MI/NRN LOWER MI REGION BY 29/12Z.
   
   MEANWHILE...WEAKNESS IN 500 MB HEIGHT FIELDS WILL PERSIST ACROSS
   CENTRAL/SRN APPALACHIANS REGION...WITH EMBEDDED VORTICITY LOBES
   CONTRIBUTING POCKETS OF LARGE SCALE ASCENT IN SUPPORT OF GEN TSTM
   ENVIRONMENT THERE.  LOW LEVEL REMAINS OF TS FAY SHOULD CONTINUE TO
   WEAKEN SLOWLY AND DRIFT NEWD.  FARTHER W...MID/UPPER RIDGING WILL
   PERSIST FROM PACIFIC OFFSHORE N-CENTRAL CA...EWD ACROSS GREAT BASIN
   AND 4-CORNERS REGIONS TO OZARKS.  DIFFUSE/ELONGATED UPPER CYCLONE --
   WITH CENTERS NOW EVIDENT OVER SRN NM AND NRN SONORA -- WILL DRIFT
   ERRATICALLY OVER THAT REGION THROUGH DAY-1 PERIOD.
   
   ...UPPER GREAT LAKES TO S-CENTRAL PLAINS...
   SCATTERED-NUMEROUS TSTMS FCST TO DEVELOP DURING AFTERNOON IN COLD
   FRONTAL ZONE...PERHAPS COALESCING INTO NEARLY CONTINUOUS ARC FROM
   UPPER MI TO KS FOR BRIEF INTERVAL BEFORE BREAKING UP INTO SHORTER
   CLUSTERED SEGMENTS DURING EVENING.  DAMAGING GUSTS AND LARGE HAIL
   WILL BE POSSIBLE.  SHORTWAVE TROUGH MOVING ACROSS MN WILL LEAD TO
   ENHANCED HEIGHT GRADIENTS ALOFT AND STRENGTHENING BUT STILL DIFLUENT
   UPPER FLOW OVER MUCH OF UPPER GREAT LAKES AND UPPER MS VALLEY
   REGION...BENEATH AND E OF 100-110 KT 250 MB JET AND 60-70 KT 500 MB
   SPEED MAX.  ALTHOUGH PREFRONTAL SFC WINDS AND CAPE OVER THIS AREA
   EACH ARE FCST TO BE WEAK...STRENGTH OF FLOW ALOFT WILL LEAD TO
   FAVORABLE DEEP-LAYER SHEAR...AND SOME POTENTIAL FOR DAMAGING WIND
   WITH BOW/LEWP FORMATIONS IN CONVECTIVE LINE.
   
   MEANWHILE STRONGEST BUOYANCY IS EXPECTED FARTHER SW ACROSS PORTIONS
   KS/MO/IL...WHERE STG SFC HEATING...MORE ROBUST MIDLEVEL LAPSE
   RATES...AND SFC DEW POINTS UPPER 60S TO 70S F COULD YIELD MLCAPES IN
   2000-3000 J/KG RANGE.  WHILE PREFRONTAL AIR MASS FROM SRN KS EWD TO
   W-CENTRAL IL WILL BE CHARACTERIZED BY WEAK LOW LEVEL
   WINDS...POTENTIAL EXISTS FOR STORMS TO FORM IN AIR IMMEDIATELY
   BEHIND SFC FRONT WHERE CONSIDERABLE MLCAPES STILL ARE PRESENT.  THIS
   REGIME MAY HELP SVR POTENTIAL BY MEANS OF NLY/NELY SFC WINDS
   ENLARGING HODOGRAPH...ESPECIALLY FOR STORMS MOVING SE TO
   SSE...THOUGH MIDLEVEL WINDS SHOULD BE WEAK.  PRIMARY STORM MODE
   SHOULD BE MULTICELLULAR...THOUGH BRIEF SUPERCELL STRUCTURES ARE
   POSSIBLE.  CONVECTIVE COVERAGE MAY DIMINISH FARTHER WSWWD INTO SWRN
   KS AND NERN NM REGION...BUT MOST INTENSE CELLS STILL MAY BE CAPABLE
   OF GUSTS/HAIL NEAR SVR LEVELS DURING LATE AFTERNOON.
   
   ...AZ....
   ANOTHER ROUND OF SCATTERED TSTMS SHOULD DEVELOP AS DIURNAL HEATING
   AND MIXING OCCUR WITHIN MOIST BOUNDARY LAYER....CHARACTERIZED BY 
   SFC DEW POINTS MID 60S DESERT VALLEYS AND PW AROUND 1.5 INCHES. 
   MAGNITUDE AND DISTRIBUTION OF STRONGEST HEATING WILL DEPEND ON
   THICKNESS/LONGEVITY OF CLOUD COVER LEFT BEHIND BY PRIOR
   CONVECTION...BUT AREAS THAT CAN REACH UPPER 90S OR HIGHER SFC TEMPS
   WILL PRESENT MOST FAVORABLE SUBCLOUD LAYERS FOR STG-SVR GUSTS TO
   REACH SFC.  SOMEWHAT DEEPER LAYER OF TIGHTER MIDLEVEL ELY-ENELY
   GRADIENT WINDS IS PROGGED THAN PERVIOUS DAY...AROUND NWRN RIM OF
   COMPLEX UPPER LOW...WITH ENE WINDS ALOFT POSSIBLE DEVELOPING SEWD
   THROUGH TUS AREA AS WELL.  THIS INDICATES CONDITIONAL POTENTIAL FOR
   BETTER ORGANIZED/AMALGAMATED OUTFLOW DEVELOPMENT OFF HIGHER TERRAIN.
    CATEGORICAL UPGRADE MAY BE NEEDED IN SUCCEEDING OUTLOOKS GIVEN
   DEPTH/STRENGTH OF FCST WINDS ALOFT TODAY.
   
   ...CENTRAL/ERN NC AND VICINITY...
   AS REMAINS OF FAY CONTINUE TO SPIN DOWN ABOVE SFC...HODOGRAPH SIZE
   SHOULD SHRINK COMMENSURATELY WITH TIME.  STG VEERING WITH HEIGHT BUT
   WEAK ABSOLUTE SPEEDS ARE FCST IN BOUNDARY LAYER ALONG AND N OF SFC
   FRONTAL ZONE...EXTENDING EWD FROM CENTRAL PORTIONS OF SLOW-MOVING
   REMAINS OF TS FAY.  GIVEN RELATED WEAKNESS OF LOW LEVEL
   WINDS...SUPERCELL OCCURRENCE AND RELATED TORNADO RISK WILL NEED
   CONSIDERABLY MORE MESOBETA TO STORM SCALE HELP THAN IN PREVIOUS DAYS
   -- EVEN INVOF SFC FRONTAL ZONE.  THEREFORE ONLY VERY MRGL TORNADO
   PROBABILITIES ARE FCST ATTM.
   
   ..EDWARDS/BRIGHT.. 08/28/2008