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Apr 29, 2014 1630 UTC Day 1 Convective Outlook

April 29, 2014

Apr 29, 2014 1630 UTC Day 1 Convective Outlook

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DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT TUE APR 29 2014

VALID 291630Z – 301200Z

…THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR SRN AND ERN MS INTO W CENTRAL/SW AL…

…THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY TO THE GREAT LAKES AND NC/VA…

…SUMMARY…
SCATTERED TO NUMEROUS SEVERE THUNDERSTORMS WILL AFFECT PORTIONS OF THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS INTO CENTRAL AND EASTERN GULF STATES THIS AFTERNOON INTO TONIGHT. SEVERAL TORNADOES…A FEW OF WHICH COULD BE STRONG…VERY LARGE HAIL AND STRAIGHT LINE DAMAGING WINDS APPEAR LIKELY.

…MS/AL AND VICINITY THROUGH TONIGHT…
A 90-120 KT MID-UPPER JET STREAK WILL TRANSLATE QUICKLY NEWD FROM TX TO THE OH VALLEY TODAY…WITH ASCENT ACCOMPANYING THE JET STREAK MANIFESTED AS THE MID CLOUD BAND FROM TXK-JBR. IN RESPONSE TO THIS JET STREAK…A WEAK SURFACE WAVE IS FORECAST TO DEVELOP NEWD FROM LA TO THE TN VALLEY…BEGINNING AT THE INTERSECTION OF THE SYNOPTIC COLD FRONT A REMNANT OUTFLOW BOUNDARY IN CENTRAL LA. IN THE WAKE OF A LARGE OVERNIGHT MCS…RAPID RECOVERY IS ENSUING FROM LA TO SRN MS AS SURFACE HEATING OCCURS AND THE MARITIME TROPICAL AIR SPREADS NEWD. THE PLUME OF STEEPER MIDLEVEL LAPSE RATES HAS BEEN CONFINED TO THE NW GULF COAST…WITH WEAKER LAPSE RATES WHERE WIDESPREAD CONVECTIVE OVERTURNING OCCURRED OVERNIGHT.

THE LOWER 70S BOUNDARY LAYER DEWPOINTS AND SURFACE TEMPERATURES WARMING INTO THE LOW 80S WILL RESULT IN MLCAPE OF 2500-3500 J/KG ACROSS LA BY MIDDAY…WHILE LESSER BUOYANCY WILL DEVELOP NEWD INTO AL. STRONG DEEP-LAYER VERTICAL SHEAR WILL SUPPORT SUPERCELL DEVELOPMENT IN THE ZONE OF RAPID DESTABILIZATION…AND A COMBINATION OF DISCRETE CELLS AND CLUSTERS WILL SUBSEQUENTLY SPREAD NEWD ACROSS MS/AL DURING THE AFTERNOON. LARGE HAIL /SOME SIGNIFICANT/ AND DAMAGING WINDS CAN BE EXPECTED WITH THESE STORMS…WITH THE POTENTIAL FOR ANOTHER MCS TO EVOLVE BY THIS EVENING ACROSS CENTRAL AL. EFFECTIVE BULK SHEAR AOA 70 KT AND EFFECTIVE SRH OF 150-200 M2/S2 IN A MOISTENING ENVIRONMENT WILL SUPPORT THE RISK FOR TORNADOES…AND POSSIBLY A COUPLE STRONG TORNADOES WITH THE MORE DISCRETE STORMS LATER THIS AFTERNOON.

…NC THIS AFTERNOON…
SURFACE HEATING ALONG A WARM FRONT WILL EVENTUALLY RESULT IN SUFFICIENT DESTABILIZATION FOR THUNDERSTORM DEVELOPMENT THIS AFTERNOON. THOUGH LAPSE RATES ARE NOT PARTICULARLY STEEP…MODERATE BUOYANCY IS STILL EXPECTED WITH THE INCREASING LOW-LEVEL MOISTURE. ALSO…VERTICAL SHEAR PROFILES ALONG THE FRONT WILL BE FAVORABLE FOR SUPERCELLS…WITH AN ATTENDANT RISK FOR A COUPLE TORNADOES IN ADDITION TO LARGE HAIL AND DAMAGING WINDS.

…OH VALLEY/GREAT LAKES THIS AFTERNOON…
SURFACE HEATING IS UNDERWAY WITHIN THE WARM SECTOR…BUT THE SURFACE FOCUS FOR STORM INITIATION IS UNCLEAR GIVEN THE SUBTLE NATURE OF THE SYNOPTIC FRONT. STILL..WITH THE EXIT REGION OF THE UPPER JET APPROACHING…SCATTERED LOW-TOPPED STORMS SHOULD FORM AND SPREAD NWD/NEWD…WITH AN ACCOMPANYING ISOLATED SEVERE RISK.

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