Jul 3, 2012 1300 UTC Day 1 Convective Outlook | |
Updated: Tue Jul 3 12:46:29 UTC 2012 | |
Probabilistic to Categorical Outlook Conversion Table |
Categorical Graphic |
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Probabilistic Tornado Graphic |
Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point. |
Probabilistic Damaging Wind Graphic |
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point. |
Probabilistic Large Hail Graphic |
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point. |
SPC AC 031242 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0742 AM CDT TUE JUL 03 2012 VALID 031300Z - 041200Z ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT ACROSS PORTIONS OF THE NRN HIGH PLAINS... ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER PARTS OF THE GREAT LAKES AND OH VALLEY... ...SYNOPSIS... STRONG SHORTWAVE TROUGH AND ASSOCIATED 60-70 KT MIDLEVEL JET STREAK OVER THE NRN INTERMOUNTAIN REGION WILL PROGRESS NEWD INTO ALBERTA/SASKATCHEWAN WITH THE SRN FRINGE OF HEIGHT FALLS/FORCING FOR ASCENT SPREADING ACROSS N-CNTRL/NERN MT. DOWNSTREAM FROM THIS FEATURE...A LOWER-AMPLITUDE SHORTWAVE TROUGH OVER THE UPPER GREAT LAKES WILL TRANSLATE SEWD THROUGH THE LOWER GREAT LAKES TO THE VICINITY OF THE NEW ENGLAND AND MID ATLANTIC COASTS BY 04/12Z. AT THE SURFACE...COLD FRONT FROM N-CNTRL MN SWWD INTO SRN SD WILL SETTLE SEWD ACROSS PORTIONS OF THE UPPER GREAT LAKES. THE WRN EXTENSION OF THE COLD FRONT WHICH HAS STALLED FROM SRN SD INTO CNTRL MT WILL LIFT NWD IN ADVANCE OF A PACIFIC FRONT ADVANCING FROM THE NRN ROCKIES INTO WRN DAKOTAS. FARTHER E...A WARM FRONT WILL LIFT NEWD THROUGH THE LOWER GREAT LAKES INTO THE HUDSON VALLEY. ...NRN HIGH PLAINS... LOW-LEVEL MASS RESPONSE TO NRN ROCKIES SHORTWAVE TROUGH --MANIFEST AS A 30-35 KT LLJ-- WILL ENHANCED THE NWWD FLUX OF A MOIST POST-FRONTAL BOUNDARY LAYER OVER THE DAKOTAS INTO ERN MT TODAY ALONG/N RETREATING WARM FRONT. THIS PROCESS WILL OCCUR BENEATH A PRONOUNCED EML...YIELDING AFTERNOON MLCAPE VALUES OF 1500-2500 J/KG. THE STRONGEST FORCING FOR ASCENT AND RESULTANT GREATER STORM COVERAGE ON THE PACIFIC FRONT IS ANTICIPATED N OF THE INTERNATIONAL BORDER. HOWEVER...THE GLANCING INFLUENCE OF UPPER SYSTEM MAY BE SUFFICIENT TO SUPPORT ISOLATED-WIDELY SCATTERED STORMS BY LATE AFTERNOON OR EVENING ACROSS PORTIONS OF NERN MT. IN THE PRESENCE OF A VERTICALLY VEERING WIND FIELD AND 35-40 KT OF DEEP-LAYER SHEAR...SETUP WILL PROMOTE SUPERCELLS AND BOWING STRUCTURES WITH A RISK FOR LARGE HAIL AND DAMAGING WINDS SPREADING EWD INTO ND TONIGHT. ...GREAT LAKES TO MID ATLANTIC COAST... WIDESPREAD CONVECTIVE OUTFLOW AND RESIDUAL CLOUD COVER ASSOCIATED WITH MULTIPLE TSTM CLUSTERS/MCSS ONGOING OVER THE GREAT LAKES CAST CONSIDERABLE UNCERTAINTY ON AIR MASS DESTABILIZATION AND LOCATION AND TIMING OF DIURNALLY ENHANCED STORM DEVELOPMENT LATER TODAY. BASED ON CURRENT OBSERVATIONAL DATA AND MODEL FORECASTS...IT APPEARS THAT SOME SUBSET OF ONGOING STORMS MAY RE-INTENSIFY BY LATE MORNING OR AFTERNOON ACROSS PARTS OF THE UPPER OH VALLEY INTO LOWER GREAT LAKES WITHIN DESTABILIZING AIR MASS INVOF RETREATING WARM FRONT. OTHER STRONG-SEVERE STORMS WILL BE POSSIBLE THIS AFTERNOON AND EVENING ALONG RESIDUAL OUTFLOW BOUNDARIES AND SYNOPTIC COLD FRONT ACROSS PORTIONS OF THE UPPER GREAT LAKES. WITH RESPECT TO THE LATTER...12Z MPX SOUNDING SAMPLED STEEP MIDLEVEL LAPSE RATES AND A MOIST BOUNDARY LAYER ON THE WRN FRINGE OF ONGOING TSTMS. CURRENT THINKING IS THAT PREVAILING WLY DEEP-LAYER FLOW FIELD SHOULD ALLOW A SIMILAR THERMODYNAMIC ENVIRONMENT TO BE ADVECTED ACROSS THE UPPER GREAT LAKES IN THE WAKE OF NOCTURNAL STORMS...AND AHEAD OF COLD FRONT. THE POTENTIAL FOR MODERATE INSTABILITY /I.E. MLCAPE VALUES OF 1500-2500 J PER KG/ WILL ALIGN WITH MODERATELY STRONG WLY FLOW /REF. 12Z MPX AND GRB SOUNDINGS/ TO SUPPORT A THREAT FOR ORGANIZED STORM MODES INCLUDING BOWS/SUPERCELLS CAPABLE OF DAMAGING WINDS AND LARGE HAIL. UPSCALE GROWTH OF DAYTIME STORMS INTO MULTIPLE NIGHTTIME COMPLEXES/MCSS IS ANTICIPATED WITH AN ISOLATED THREAT FOR HAIL AND LOCALLY DAMAGING WINDS SPREADING EWD TOWARD THE HUDSON VALLEY AND MID ATLANTIC COAST. ...CNTRL/SRN APPALACHIANS INTO GULF COAST STATES... 12Z REGIONAL SOUNDINGS INDICATE THE POTENTIAL FOR MODERATE-STRONG AIR MASS DESTABILIZATION TODAY OWING TO THE PRESENCE OF A MOIST BOUNDARY LAYER AND DAYTIME HEATING. TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND INTENSITY THIS AFTERNOON ALONG THE HIGH TERRAIN...DEVELOPING SEA BREEZE FRONT...AND OUTFLOW BOUNDARIES REMNANT FROM MONDAY AFTERNOON/EVENING STORMS. WHILE WEAK VERTICAL SHEAR WILL LIMIT THE POTENTIAL FOR STORM ORGANIZATION/LONGEVITY...ISOLATED OCCURRENCES OF DAMAGING WIND AND HAIL ARE POSSIBLE. ..MEAD/HURLBUT.. 07/03/2012 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z