SPC Aug 18, 2012 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook
DAY 3 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0220 AM CDT SAT AUG 18 2012 VALID 201200Z - 211200Z ...SYNOPSIS... A LARGE-SCALE UPPER-LEVEL TROUGH SHOULD REMAIN ANCHORED FROM THE CNTRL GREAT LAKES TO THE LOWER MS VALLEY. GUIDANCE DIFFERS GREATLY ON THE HANDLING OF INDIVIDUAL SHORT WAVE IMPULSES EVOLVING WITHIN AND EAST OF THE TROUGH. AN UPPER-LEVEL RIDGE WILL PERSIST FROM THE SOUTHWEST TO THE NRN ROCKIES...WITH A COUPLE OF WEAK IMPULSES EXPECTED TO DIVE SEWD ACROSS THE HIGH PLAINS. ...SOUTHEAST TO LOWER MID-ATLANTIC... DISCREPANCIES WITH THE EVOLUTION OF INDIVIDUAL SHORT WAVE IMPULSES AND ASSOCIATED MASS RESPONSE DURING THE D2 PERIOD CONTINUE INTO D3 AND RESULT IN LARGE THERMODYNAMIC/KINEMATIC DIFFERENCES THAT PLAGUE THE ENVIRONMENTAL ASSESSMENT FOR THIS OUTLOOK. SOME OF THE GUIDANCE THAT DEPICT DEEPER LOW-LEVEL CYCLOGENESIS SUGGEST A BROAD SWATH OF LOWER 70S SURFACE DEW POINTS WILL AID IN STRONG BUOYANCY /NOTED IN ETA-KF AND WRF-ARW MEMBERS OF THE 21Z SREF/ AND WILL BE COINCIDENT WITH ROBUST LOW/MID-LEVEL SHEAR. THE 00Z NAM WITH ONLY MODEST LOW-LEVEL MASS RESPONSE...SUGGESTS INSTABILITY WILL BE MINIMAL WITH RATHER POOR MID-LEVEL LAPSE RATES AND A DRIER BOUNDARY LAYER...SUPPORTED BY WRF-NMM MEMBERS OF THE 21Z SREF. WITH NON-NCEP GUIDANCE PREFERRED THIS OUTLOOK BY HPC...THE WIDE VARIATION IN THERMODYNAMIC PARAMETERS WITHIN NCEP GUIDANCE...AND THE LIKELIHOOD FOR PRECEDING CONVECTION ON D1/D2...CONFIDENCE IS VERY LOW IN WHAT THE WARM SECTOR ENVIRONMENT WILL LOOK LIKE. FOR NOW...WILL BROAD-BRUSH WITH LOW SEVERE PROBABILITIES. ...SRN HIGH PLAINS... GUIDANCE IS FAIRLY CONSISTENT IN DEPICTING WEAK MID-LEVEL IMPULSES PROGRESSING SEWD BETWEEN THE WRN RIDGE AND CNTRL/ERN CONUS TROUGH ON MON. THESE SHOULD BE FAVORABLY TIMED WITH THE DIURNAL HEATING CYCLE AND WOULD LIKELY YIELD A TSTM CLUSTER FORMING INVOF RATON MESA WITHIN A WEAKLY BUOYANT AIR MASS. ALTHOUGH FLOW FIELDS MAY REMAIN MODEST...NEARLY STRAIGHT-LINE HODOGRAPHS SHOULD BE SUFFICIENT FOR MARGINAL SUPERCELLS CAPABLE OF LOCALIZED SEVERE HAIL/WIND. ..GRAMS.. 08/18/2012 Read more

http://www.spc.noaa.gov/products/outlook/day3otlk_0730.html