SWODY2
SPC AC 120532
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1232 AM CDT WED MAY 12 2010
VALID 131200Z - 141200Z
...THERE IS A SLGT RISK OF SVR TSTMS THU ACROSS THE MIDDLE
MISSISSIPPI AND OHIO VALLEYS....
...SYNOPSIS...
MODELS CONTINUE TO INDICATE THAT A SUBTROPICAL RIDGE...NOW BUILDING
ACROSS THE EASTERN GULF OF MEXICO INTO THE SOUTHEASTERN U.S. AND
ADJACENT PORTIONS OF THE WESTERN ATLANTIC...WILL REMAIN STRONG
THROUGH THIS FORECAST PERIOD. UPPER TROUGHING IS EXPECTED TO LINGER
TO ITS WEST...ACROSS CALIFORNIA AND THE CENTRAL/SOUTHERN PLATEAU AND
ROCKIES...BUT A SIGNIFICANT SHORT WAVE IMPULSE EMANATING FROM
IT...INCLUDING THE REMNANTS OF AN EMBEDDED CLOSED LOW...LIKELY WILL
CONTINUE LIFTING AROUND THE PERIPHERY OF THE RIDGE INTO THE UPPER
GREAT LAKES REGION.
A SEASONABLY MOIST...POTENTIALLY UNSTABLE AIR MASS HAS ALREADY
RETURNED TO A BROAD AREA OF THE CENTRAL AND SOUTHEASTERN U.S...AND
THE EVOLVING UPPER PATTERN SHOULD GENERALLY MAINTAIN THIS.
HOWEVER...A COLD FRONT ASSOCIATED WITH THE UPPER TROUGH IS EXPECTED
TO ADVANCE SOUTHWARD THROUGH THE SOUTHERN PLAINS...AND A BIT MORE
SLOWLY EAST/SOUTHEASTWARD THROUGH THE MIDDLE MISSISSIPPI AND OHIO
VALLEYS. THIS FEATURE...PRE-FRONTAL CONVECTIVE BOUNDARIES...AND
CONVECTIVELY GENERATED OR ENHANCED VORTICITY MAXIMA ARE EXPECTED TO
PROVIDE THE FOCUS FOR CONSIDERABLE THUNDERSTORM ACTIVITY
THURSDAY/THURSDAY NIGHT...FROM THE SOUTHERN PLAINS NORTHEASTWARD
THROUGH THE OHIO VALLEY...APPALACHIANS AND PORTIONS OF THE MID
ATLANTIC STATES.
...MIDDLE MISSISSIPPI AND OHIO VALLEYS...
A WEAK FRONTAL WAVE IS EXPECTED TO ACCOMPANY THE UPPER IMPULSE...
MIGRATING FROM UPPER PORTIONS OF THE MIDDLE MISSISSIPPI VALLEY
THROUGH THE GREAT LAKES DURING THE PERIOD. PERHAPS MORE
IMPORTANTLY...MODELS HAVE BEEN SUGGESTIVE THAT AT LEAST WEAK
MID-LEVEL HEIGHT FALLS AND STRENGTHENING WEST SOUTHWESTERLY
LOWER/MID TROPOSPHERIC FLOW WILL OVERSPREAD THE WARM SECTOR...NORTH
AND WEST OF THE OHIO RIVER. IN PARTICULAR...MOST MODELS GENERALLY
INDICATE A 40+ KT 850 MB/60-70 KT 500 MB JET STREAK WILL NOSE
NORTHEASTWARD INTO AND THROUGH THE OHIO VALLEY COINCIDENT WITH
DAYTIME BOUNDARY LAYER DESTABILIZATION. SREF GUIDANCE INDICATES
THAT SURFACE DEW POINTS IN THE MID/UPPER 60S ARE
LIKELY...CONTRIBUTING TO MIXED LAYER CAPE ON THE ORDER OF 2000 J/KG.
IT APPEARS THAT LOW-LEVEL WARM ADVECTION AHEAD OF THE WAVE COULD
CONTRIBUTE TO DISCRETE STORM DEVELOPMENT...POSSIBLY SUPERCELLS WITH
A RISK FOR TORNADOES...NEAR A RETREATING WARM FRONT ACROSS PARTS OF
NORTHERN INDIANA AND OHIO INTO THE NORTH CENTRAL APPALACHIANS BY
EARLY THURSDAY AFTERNOON. THEREAFTER...FORCING ASSOCIATED WITH THE
UPPER IMPULSE SPREADING OUT OF MISSOURI INTO ILLINOIS/INDIANA IS
EXPECTED TO SUPPORT ADDITIONAL STRONG/SEVERE STORM DEVELOPMENT WITH
A TENDENCY TO GROW AND ORGANIZE INTO ONE OR MORE MESOSCALE
CONVECTIVE SYSTEMS. GIVEN THE STRENGTH OF THE DEEP LAYER MEAN
FLOW...THERMODYNAMIC PROFILES PROBABLY WILL BE CONDUCIVE FOR THE
DEVELOPMENT OF POTENTIALLY DAMAGING SURFACE GUSTS...IN ADDITION TO
THE RISK FOR LARGE HAIL. ACTIVITY LIKELY WILL SPREAD EASTWARD
THROUGH MUCH OF THE OHIO VALLEY BEFORE WEAKENING THURSDAY NIGHT.
...SOUTHERN PLAINS INTO THE OZARKS...
UNCERTAINTY IS GROWING CONCERNING SEVERE POTENTIAL FOR THIS PERIOD
DUE TO THE TENDENCY FOR WEAKENING FLOW FIELDS...RISING MID-LEVEL
HEIGHTS...AND POSSIBLE FASTER SOUTHWARD COLD FRONTAL SURGE THAN
EARLIER EXPECTED. THE BOUNDARY LAYER AHEAD OF THE COLD FRONT IS
LIKELY TO REMAIN MODERATE TO STRONGLY UNSTABLE...HOWEVER...SO THE
RISK FOR ISOLATED TO WIDELY SCATTERED LATE AFTERNOON/EVENING STORMS
MAY NOT BE COMPLETELY NEGLIGIBLE.
..KERR.. 05/12/2010
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