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Apr 28, 2014 0600 UTC Day 1 Convective Outlook

April 28, 2014

Apr 28, 2014 0600 UTC Day 1 Convective Outlook

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DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0104 AM CDT MON APR 28 2014

VALID 281200Z – 291200Z

…THERE IS A MDT RISK OF SVR TSTMS FROM PORTIONS OF WRN AND MIDDLE TN SWWD ACROSS NWRN AL/NRN AND CENTRAL MS INTO FAR NERN LA…

…THERE IS A SLGT RISK OF SVR TSTMS IN AN ARC FROM SERN IA SEWD INTO THE OH VALLEY…AND THEN SWD/SWWD ACROSS THE MID SOUTH INTO THE CENTRAL GULF COASTAL REGION…

…SUMMARY…
WIDESPREAD SEVERE STORMS — INCLUDING STRONG TORNADOES…DAMAGING WINDS AND VERY LARGE HAIL — ARE EXPECTED MONDAY AND MONDAY NIGHT OVER PARTS OF THE EASTERN UNITED STATES BOUNDED BY AN AREA FROM ROUGHLY THE MISSISSIPPI VALLEY ON THE WEST…THE APPALACHIANS ON THE EAST…THE MIDWEST STATES ON THE NORTH…AND THE GULF OF MEXICO ON THE SOUTH. THE GREATEST RISK IS FORECAST FROM SOUTHERN KENTUCKY AND TENNESSEE SOUTH INTO MISSISSIPPI AND ALABAMA.

…SYNOPSIS…
A LARGE UPPER LOW INITIALLY FORECAST OVER THE NEB VICINITY IS PROGGED TO SHIFT SLOWLY ESEWD WITH TIME…REACHING THE SRN IA/NRN MO AREA LATE. THE CYCLONIC FLOW FIELD SURROUNDING THIS LOW WILL COVER A LARGE PORTION OF THE COUNTRY THROUGH THE PERIOD.

AT THE SURFACE…AN OCCLUDED LOW INITIALLY OVER ERN NEB IS FORECAST TO DRIFT SLOWLY EWD…WHILE A TRAILING COLD FRONT EXITS THE CENTRAL AND SRN PLAINS AND REACHES THE MID/LOWER MS VALLEY AREA BY EVENING. MEANWHILE…A WARM FRONT IS PROGGED TO LINGER ACROSS THE MIDWEST STATES — WITH A BROAD/MOIST WARM SECTOR EXTENDING FROM THE OH VALLEY REGION TO THE GULF COAST EXPECTED TO BE THE FOCUS AREA FOR ANOTHER ROUND OF STRONG/SEVERE STORMS ON MONDAY.

…CENTRAL KY SSWWD ACROSS TN INTO NRN AND WRN AL/MS/NERN LA…
A RATHER COMPLEX SCENARIO APPEARS TO BE EVOLVING FOR MONDAY…AS AN MCS ONGOING ACROSS THE LOWER OH VALLEY AREA AND A SECOND AREA OF STORMS OCCURRING IN A BROKEN LINE FROM S CENTRAL MO SWWD INTO NERN TX WILL AFFECT PORTIONS OF MONDAY/S SEVERE RISK AREA THE REMAINDER OF THE NIGHT.

MODELS CONTINUE TO SUGGEST THAT THE AFOREMENTIONED LINE OF STORMS MOVING EWD TOWARD THE MS VALLEY WILL WEAKEN DURING THE MID MORNING HOURS…WHILE THE MCS ONGOING OVER THE LOWER OH VALLEY MOVES MORE QUICKLY EWD ACROSS THE MID OH VALLEY. AS THIS SCENARIO SEEMS REASONABLE…IT WOULD APPEAR THAT SOME HEATING WILL COMMENCE ACROSS THE KY/TN/MS/AL VICINITY BY AFTERNOON…WHICH — COMBINED WITH THE MOIST AIRMASS IN PLACE — SHOULD YIELD AMPLE DESTABILIZATION FOR REDEVELOPMENT OF CONVECTION ACROSS THE SLIGHT/MDT RISK AREAS. ATTM…IT APPEARS THAT A COMPLEX/MIXED-MODE EVENT WILL EVOLVE…BUT WITH ROTATING/SUPERCELL STORMS LIKELY GIVEN THE FAVORABLY SHEARED ENVIRONMENT. THUS…ALONG WITH RISK FOR LARGE HAIL AND DAMAGING WINDS…TORNADOES ARE ALSO EXPECTED — INCLUDING POTENTIAL FOR A FEW STRONG TORNADOES. STORMS WILL SPREAD EWD WITH TIME INTO THE EVENING…APPROACHING THE APPALACHIANS OVERNIGHT. WHILE SOME DIURNAL WEAKENING IS EXPECTED…SOME SEVERE RISK IS LIKELY TO LINGER THROUGH THE END OF THE PERIOD.

…PARTS OF IA/IL AND VICINITY…
AN ARCING BAND OF SHOWERS AND LOW-TOPPED THUNDERSTORMS ARE FORECAST TO DEVELOP DURING THE AFTERNOON INVOF ERN IA/WRN IL…NEAR A TRIPLE POINT E OF THE SURFACE LOW CROSSING WRN IA DURING THE AFTERNOON. WITH DIURNAL HEATING SUPPORTING DEVELOPMENT OF ROUGHLY 500 TO 1000 J/KG MIXED-LAYER CAPE…A FEW STRONGER STORMS ARE FORECAST TO DEVELOP WITHIN THE BAND. STORM LONGEVITY/INTENSITY WILL BE AIDED BY AN AMPLY SHEARED ENVIRONMENT — PARTICULARLY JUST TO THE N SIDE OF THE OCCLUDED/WARM FRONTS — WHERE LOW-LEVEL ELYS VEERING WITH HEIGHT TO SLY AT MID-LEVELS WILL RESULT IN WIND PROFILES SUPPORTIVE OF UPDRAFT ROTATION. ALONG WITH POTENTIAL FOR HAIL…ISOLATED TORNADOES WILL ALSO BE POSSIBLE BEFORE STORMS BEGIN TO DIURNALLY WEAKEN TOWARD SUNSET.

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