SWODY1
SPC AC 150556
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT FRI MAY 15 2009
VALID 151200Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN AND CNTRL PLAINS
INTO THE MIDDLE MS AND OH VALLEYS...
...SYNOPSIS...
PROGRESSIVE UPPER TROUGH OVER THE NRN ROCKIES WILL REACH THE UPPER
MS VALLEY BY FRIDAY EVENING AND THE UPPER GREAT LAKES FRIDAY NIGHT.
ATTENDANT LEE CYCLONE WILL ADVANCE EWD TO MN BY LATE AFTERNOON WITH
TRAILING COLD FRONT EXTENDING SWWD THROUGH THE CNTRL PLAINS. DRYLINE
WILL EXTEND THROUGH WRN TX INTO SWRN KS WHERE IT WILL INTERSECT THE
SWD ADVANCING COLD FRONT. FRONTAL BOUNDARY CURRENTLY EXTENDING FROM
OK EWD THROUGH THE TN VALLEY WILL LIFT NWD THROUGH THE MIDDLE MS AND
OH VALLEYS DURING THE DAY. SLOW MOVING VORT MAX OVER NRN MEXICO WILL
MOVE INTO WRN TX DURING THE AFTERNOON.
...MID MS THROUGH OH VALLEYS...
STORMS WILL BE ONGOING EARLY FRIDAY FROM NERN KS THROUGH NRN MO AND
IA WITHIN ZONE OF ISENTROPIC LIFT ASSOCIATED WITH SWLY LOW LEVEL
JET. THIS FEATURE WILL SLOWLY DEVELOP ENEWD TOWARD THE GREAT LAKES
DURING THE DAY WITHIN ZONE OF LARGE SCALE FORCING FOR ASCENT
ASSOCIATED WITH EWD MIGRATING SHORTWAVE TROUGH. A MOIST WARM SECTOR
WITH MID-UPPER 60S DEWPOINTS WILL ADVECT NWD TO THE SOUTH OF ONGOING
STORMS AND CONTRIBUTE TO POTENTIAL FOR MODERATE INSTABILITY AS THE
BOUNDARY LAYER WARMS. INITIAL STORMS WILL LIKELY BE ELEVATED...BUT
THREAT FOR SURFACE BASED STORMS WILL INCREASE AS DIABATIC HEATING
COMMENCES. THIS REGION WILL REMAIN WITHIN SRN FRINGE OF STRONGER
WLYS WITH 40 KT BULK SHEAR SUPPORTIVE OF ORGANIZED STORMS INCLUDING
SUPERCELLS AND BOWING SEGMENTS. LARGE HAIL AND DAMAGING WIND WILL BE
POSSIBLE WITH THE STRONGER STORMS. THE EWD MIGRATING LOW LEVEL JET
WILL MAINTAIN SUFFICIENT 0-1 KM HODOGRAPHS FOR A THREAT OF ISOLATED
TORNADOES DURING THE AFTERNOON AND EARLY EVENING.
...CNTRL AND SRN PLAINS...
MID-UPPER 60S BOUNDARY LAYER DEWPOINTS HAVE ADVECTED NWWD BENEATH 8+
C/KM 700-500 MB LAPSE RATES...RESULTING IN A RESERVOIR OF STRONG
INSTABILITY OVER THE SRN PLAINS. THE ATMOSPHERE WILL DESTABILIZE
THROUGH MUCH OF KS AS MOISTURE ADVECTS FARTHER NWD IN WAKE OF
RETREATING WARM FRONT. MLCAPE FROM 2500-3000 J/KG WILL BE LIKELY
FROM PORTIONS OF KS THROUGH THE SRN PLAINS AS THE BOUNDARY LAYER
WARMS FRIDAY AFTERNOON. STORMS SHOULD INITIATE BY MID-LATE AFTERNOON
ALONG PROGRESSIVE COLD FRONT ACROSS KS AND DEVELOP SEWD. MUCH OF
THIS REGION WILL REMAIN ON SRN FRINGE OF STRONGER WLYS WITH BULK
SHEAR GENERALLY AOB 35 KT. GIVEN POTENTIAL FOR STRONG UPDRAFT
ACCELERATIONS DUE TO STEEP LAPSE RATES AND LARGE CAPE WITHIN THE
MODESTLY SHEARED ENVIRONMENT...SOME STORMS WILL LIKELY DEVELOP
SUPERCELL STRUCTURES AND BECOME CAPABLE OF PRODUCING VERY LARGE
HAIL. AS THE LOW LEVEL JET SHIFTS AWAY FROM THE REGION...0-1 KM
HODOGRAPHS WILL NOT BE PARTICULARLY LARGE. HOWEVER...STRONG UPDRAFT
ACCELERATIONS ASSOCIATED WITH SUPERCELLS DEVELOPING IN VICINITY OF
THE BOUNDARY SUGGEST ISOLATED TORNADOES WILL ALSO BE POSSIBLE
THROUGH EARLY-MID EVENING. STORMS MAY EVOLVE INTO MORE LINEAR MODES
OVERNIGHT.
OTHER MORE HIGH BASED STORMS ARE EXPECTED ALONG THE DRYLINE WHERE
VERTICAL SHEAR WILL BE SOMEWHAT WEAKER. LARGE HAIL AND ISOLATED
DAMAGING WIND WILL BE THE MAIN THREATS WITH THIS ACTIVITY.
...UPPER MS VALLEY REGION...
COLDER TEMPERATURES ALOFT WILL COMPENSATE FOR MORE LIMITED MOISTURE
IN THIS REGION. AN AXIS OF MARGINAL INSTABILITY IS EXPECTED IN
PRE-FRONTAL WARM SECTOR. STORMS WILL LIKELY DEVELOP ALONG FRONT
WITHIN ZONE OF LARGE SCALE ASCENT ASSOCIATED WITH EWD ADVANCING
SHORTWAVE TROUGH. VERTICAL SHEAR WILL SUPPORT THE POTENTIAL FOR
ORGANIZED STORMS INCLUDING SUPERCELLS WITH ISOLATED HAIL AND
DAMAGING WIND POSSIBLE. AT THIS TIME...IT APPEARS THE THERMODYNAMIC
ENVIRONMENT COULD POSE A LIMITING FACTOR. THIS AREA WILL BE
MONITORED FOR A POSSIBLE SLIGHT RISK IN LATER OUTLOOKS.
..DIAL/GRAMS.. 05/15/2009
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