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Apr 28, 2014 1730 UTC Day 2 Convective Outlook

April 28, 2014

Apr 28, 2014 1730 UTC Day 2 Convective Outlook

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DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT MON APR 28 2014

VALID 291200Z – 301200Z

…THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF ALABAMA…MISSISSIPPI…SOUTHEASTERN LOUISIANA…AND THE WESTERN FLORIDA PANHANDLE…

…THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE ACROSS MUCH OF THE GULF COAST AND SOUTHEAST STATES TO THE MID-ATLANTIC AND NORTHWARD INTO PORTIONS OF THE LOWER GREAT LAKES AND OHIO VALLEY REGION…

…SUMMARY…
NUMEROUS SEVERE THUNDERSTORMS…INCLUDING TORNADOES…WILL BE POSSIBLE ON TUESDAY ACROSS PORTIONS OF MISSISSIPPI…ALABAMA…SOUTHEASTERN LOUISIANA…AND THE WESTERN FLORIDA PANHANDLE. SCATTERED SEVERE THUNDERSTORMS ARE POSSIBLE ELSEWHERE FROM PORTIONS OF THE CENTRAL GULF COAST REGION ACROSS THE SOUTHEAST UNITED STATES TO THE MID-ATLANTIC…WITH ISOLATED SEVERE STORMS POSSIBLE NORTHWARD INTO THE LOWER GREAT LAKES AND OHIO VALLEY REGION.

…SYNOPSIS…
A DEEP MID-LEVEL LOW WILL SLOWLY DRIFT NWD ACROSS THE UPPER MIDWEST. EMBEDDED WITHIN BROADLY CYCLONIC FLOW ENCIRCLING THE LOW…TWO MID-LEVEL JET STREAKS WILL FOCUS THE SEVERE RISK ON TUESDAY. THE FIRST JET STREAK CURRENTLY PIVOTING THROUGH THE ERN SEMICIRCLE OF THE LOW WILL ADVANCE FROM THE MID-SOUTH TO THE ERN GREAT LAKES…WHILE AN UPSTREAM JET MAX ADVANCES FROM THE SRN PLAINS TO THE TN VALLEY. LOW-LEVEL JET STREAMS ACCOMPANYING BOTH OF THESE FEATURES WILL MAINTAIN POLEWARD FLUXES OF MARITIME TROPICAL AIR OVER THE SERN STATES IN ADVANCE OF A FRONT THAT WILL BEGIN TO ACCELERATE EWD BY LATE IN THE PERIOD.

…CENTRAL GULF COAST VICINITY TO THE SOUTHEAST STATES AND MID-ATLANTIC…
SLY FLOW IN ADVANCE OF THE FRONT WILL MAINTAIN A REGION OF MID/UPPER 60S-LOWER 70S SFC DEWPOINTS BENEATH STEEP MID-LEVEL LAPSE RATES. ASCENT ACCOMPANYING THE LLJ ATTENDANT TO THE FIRST JET STREAK WILL LIKELY SUSTAIN A THREAT FOR SEVERE THUNDERSTORMS EWD FROM PORTIONS OF THE TN VALLEY TO THE SRN APPALACHIANS SWD TO THE GULF COAST INTO THE MORNING HOURS OF TUESDAY. WITH DIURNAL HEATING OF THE MOIST BOUNDARY LAYER…MLCAPE WILL LIKELY REACH 1000-2500 J/KG ACROSS A BROAD WARM SECTOR FROM THE LOWER MS VALLEY TO THE SOUTHEAST STATES AND MID ATLANTIC. WHILE THERE IS UNCERTAINTY REGARDING THE EVENTUAL EVOLUTION OF THE MORNING CONVECTION…IT IS EXPECTED THAT THE SVR RISK WILL INCREASE ACROSS THE WARM SECTOR OWING TO /1/ DIURNAL INTENSIFICATION OF MORNING CONVECTION…/2/ ADDITIONAL CONVECTION DEVELOPING ALONG ITS ASSOCIATED OUTFLOW BOUNDARIES…AND /3/ AFTERNOON CONVECTIVE DEVELOPMENT ACROSS PORTIONS OF CNTRL/ERN MS INTO SERN LA. WITH EFFECTIVE BULK SHEAR MAGNITUDES OVER 35 KT ACROSS THIS BROAD WARM SECTOR…ORGANIZED SEVERE STORMS WITH DAMAGING WINDS…SVR HAIL…AND TORNADOES WILL BE POSSIBLE.

THE GREATEST SVR RISK WILL EXTEND ACROSS THE MODERATE RISK AREA COVERING PORTIONS OF ALABAMA…MISSISSIPPI…SOUTHEASTERN LOUISIANA…AND THE WESTERN FLORIDA PANHANDLE…AS 70-90 KT OF H5 FLOW OVERSPREADS THIS REGION IN ASSOCIATION WITH THE SECOND MID-LEVEL JET STREAK. DIURNAL CONVECTIVE INITIATION IS EXPECTED TO BE ENHANCED BY INSOLATION SUCCEEDING EARLIER-DAY ACTIVITY ACROSS PARTS OF MS INTO SERN LA…AND AIDED BY GLANCING ASCENT FROM THE MID-LEVEL JET MAX. ATTENDANT EFFECTIVE BULK SHEAR MAGNITUDES OF 50-70 KT WILL SUPPORT SUSTAINED ROTATING UPDRAFTS/SUPERCELLS DEVELOPING ALONG THE FRONT DURING THE AFTERNOON…WHICH WILL SPREAD EWD INTO AL THROUGH THE EVENING. LARGE HAIL…SOME POSSIBLY SIGNIFICANT…ALONG WITH DAMAGING WINDS…AND TORNADOES WILL ALL BE POSSIBLE. SOME RISK FOR STRONG TORNADOES WILL EXIST…ESPECIALLY IF CONVECTION CAN EVOLVE AHEAD OF THE SFC BOUNDARY WHERE SFC WINDS REMAIN RELATIVELY MORE BACKED AND IN PROXIMITY TO A FRONT-PRECEDING 35-40-KT H85 LLJ.

…PORTIONS OF THE LOWER GREAT LAKES AND OHIO VALLEY REGION…
RELATIVELY LOWER THETA-E WILL EXIST NORTHWARD WITH MIDDLE 50S SFC DEWPOINTS EXTENDING NWD INTO SERN LOWER MI. HOWEVER…WITH THE COMBINATION OF SOME SFC HEATING IN THE WAKE OF CONVECTION EARLIER IN THE DAY…THERE WILL BE SUFFICIENT BUOYANCY FOR ISOLATED SEVERE STORMS WITH DMGG WINDS AND SVR HAIL…ESPECIALLY GIVEN OVERLYING STRONG MID-LEVEL FLOW. GIVEN A MODEST LLJ…SOME TORNADO RISK MAY EVOLVE FROM PARTS OF MIDDLE TN TO THE OH VALLEY AND POSSIBLY LOWER MI…BUT THIS WILL BE CONTINGENT ON MORE APPRECIABLE DIURNAL DESTABILIZATION FOR WHICH UNCERTAINTY REMAINS.

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