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May 13, 2014 1730 UTC Day 2 Convective Outlook

May 13, 2014

May 13, 2014 1730 UTC Day 2 Convective Outlook

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DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1224 PM CDT TUE MAY 13 2014

VALID 141200Z – 151200Z

…THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY TO THE OH VALLEY REGION…

…SUMMARY…
ISOLATED SEVERE THUNDERSTORMS ARE LIKELY ACROSS PARTS OF THE MISSISSIPPI…TENNESSEE…AND OHIO VALLEYS BEGINNING WEDNESDAY AFTERNOON. DAMAGING WINDS SHOULD BE THE PRIMARY HAZARD. HOWEVER…A FEW TORNADOES WILL ALSO BE POSSIBLE FROM NORTHERN KENTUCKY AND SOUTHEASTERN INDIANA INTO SOUTHWEST AND CENTRAL OHIO.

…SYNOPSIS…
MODULATIONS TO THE MID-LEVEL HEIGHT PATTERN IN RESPONSE TO A SHORTWAVE TROUGH DIGGING SWD FROM THE CANADIAN PRAIRIES WILL ENCOURAGE THE AMPLIFICATION AND EWD/ENEWD PROGRESSION OF A LOWER-LATITUDE IMPULSE FROM THE SRN PLAINS TO THE MS VALLEY AND SWRN GREAT LAKES REGION. GEOSTROPHIC ADJUSTMENT ATTENDANT TO A STRENGTHENING MID/UPPER JET STREAK E OF THE LATTER PERTURBATION WILL ENHANCE SFC CYCLOGENESIS OVER PARTS OF THE LOWER MS VALLEY AND TN VALLEY WITH THE ENSUING SFC CYCLONE DEVELOPING NNEWD TO THE LOWER GREAT LAKES ALONG A FORMERLY STALLED BAROCLINIC ZONE. THE RELATED SFC FRONT WILL ACCELERATE EWD TO THE S OF THE LOW…WHILE A STRENGTHENING LLJ PROMOTES POLEWARD FLUXES OF WARM/MOIST AIR TO THE E/NE OF THE CYCLONE. THIS WILL EFFECTIVELY ESTABLISH A WARM FRONT E OF THE LOW…WHICH WILL RETREAT NWD OVER THE OH VALLEY REGION THROUGH THE PERIOD.

…OH VALLEY REGION TO CENTRAL GULF COAST…
A PLUME OF MOISTURE-RICH AIR WITHIN THE BOUNDARY LAYER — E.G. MIDDLE/UPPER 60S SFC DEWPOINTS — WILL CONTINUE TO BE REINFORCED NNEWD FROM THE CNTRL GULF COAST TO THE OH VALLEY E OF THE SFC FRONT. GENERALLY POOR MID-LEVEL LAPSE RATES…AND AREAS OF ANTECEDENT CLOUDS/PRECIPITATION…WILL LARGELY DAMPEN THE DIURNAL BOOST TO BUOYANCY. HOWEVER…DIABATIC SFC-LAYER HEATING SHOULD BE SUFFICIENT TO SUPPORT 500-1000 J/KG OF MLCAPE INTO THE AFTERNOON. LIMITED CAPPING WILL LIKELY PROMOTE AN UPTICK IN CONVECTIVE ACTIVITY/INTENSITY THROUGH THE DAY…ESPECIALLY AS MID-LEVEL HEIGHT FALLS/ASCENT OVERSPREAD THE UNSTABLE AIR MASS E OF THE FRONT. WHILE THE STRONGEST MID-LEVEL FLOW ACCOMPANYING THE AFOREMENTIONED JET STREAK WILL LIKELY RESIDE ON THE COOL SIDE OF THE BOUNDARY…THE PRESENCE OF 35-50-KT H5 SSWLYS WILL PROVIDE SUFFICIENT DEEP SHEAR OVER THE WARM SECTOR FOR ORGANIZED CONVECTION/MULTICELL CLUSTERS. WATER LOADING AND MODESTLY ENHANCED CONVECTIVE MOMENTUM TRANSPORT AIDED BY 30-40 KT H7 FLOW WILL BE SUFFICIENT FOR ISOLATED INSTANCES OF DMGG WIND GUSTS WITH THIS ACTIVITY.

SOMEWHAT GREATER CONCERN FOR SVR STORMS — INCLUDING POSSIBLE TORNADOES — WILL EXIST ACROSS PORTIONS OF THE OHIO VALLEY…PARTICULARLY FROM NRN KY AND SERN INDIANA INTO SW AND CNTRL OHIO. THESE AREAS WILL BE IN CLOSER PROXIMITY TO THE SFC CYCLONE WHERE A 30-45-KT H85 JET WILL CONCENTRATE ENHANCED LOW-LEVEL SHEAR. MESOVORTICES EMBEDDED WITHIN SHORT LINE SEGMENTS…AND PERHAPS A FEW SUPERCELL STRUCTURES…COULD EVOLVE FROM THIS ACTIVITY AND LOCALLY ENHANCE THE SVR RISK. ANY SUPERCELLS INTERACTING WITH THE NWD-RETREATING WARM FRONTAL ZONE — I.E. A FOCUSED AREA OF BACKED SFC WINDS YIELDING 150-200 M2/S2 OF EFFECTIVE SRH — WILL POSE THE GREATEST TORNADO POTENTIAL. HOWEVER…SUBSTANTIAL UNCERTAINTY EXISTS IN THIS RISK OWING TO /1/ THE POTENTIAL FOR MORNING CONVECTION TO HINDER BUOYANCY…AND /2/ THE POTENTIAL FOR EARLY DEVELOPMENT OF AFTERNOON CONVECTION OUT OF PHASE WITH THE MORE ROBUST STRENGTHENING OF THE LLJ. AS SUCH…HIGHER SVR PROBABILITIES HAVE NOT BEEN INCLUDED AT THIS TIME.

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