SPC AC 201932
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0232 PM CDT THU MAY 20 2010
VALID 202000Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM CNTRL/E TX INTO THE LWR MS
AND LWR TN VLYS...
.CHANGES TO THE PREV OTLK: ADJUST SLGT RISK SWD BEHIND THE SURGING
OUTFLOW ACROSS NWRN MS...NRN LA...SRN AR. REST UNCHANGED.
...CNTRL/E TX INTO THE LWR MS/TN VLYS...
ARCING OUTFLOW CONTINUES TO PROGRESS SEWD ACROSS NWRN MS AND NRN LA.
MULTI-BANDED TSTMS CONTINUE ALONG/AHEAD OF THE FEATURE ACROSS
MIDDLE/WRN TN SWD INTO WRN AL/CNTRL MS AND NRN LA AMIDST FAVORABLE
VERTICAL SHEAR TO SUPPORT MULTICELL/ISOLD SUPERCELL STORM MODES
CAPABLE OF DMGG WINDS...LARGE HAIL AND BRIEF TORNADOES.
FARTHER W...WITHIN COMPARATIVELY STEEPER MID-LVL LAPSE
RATES/BUOYANCY...SUPERCELL STORMS WERE BACKBUILDING ALONG WRN EXTEND
OF THE OUTFLOW/SEGMENTED CDFNT FROM NE-NCNTRL TX WHERE SRN EXTENT OF
MODEST UPR FLOW/HEIGHT FALLS EXIST. LLVL FLOW IS NOT PARTICULARLY
STRONG...BUT VIGOROUS STRETCHING INVOF THE BOUNDARY HAS RESULTED IN
BRIEF TORNADOES. OTHERWISE...VERY LARGE HAIL CAN BE EXPECTED.
...REMAINDER OF DISCO UNCHANGED...
..RACY/CORFIDI/JIRAK.. 05/20/2010
.PREV DISCUSSION... /ISSUED 1126 AM CDT THU MAY 20 2010/
...SYNOPSIS...
KS UPR LOW EXPECTED TO CONTINUE ENE INTO IA AND SLOWLY WEAKEN THIS
PERIOD AS LEAD IMPULSE ASSOCIATED WITH POTENT NE PACIFIC TROUGH
SWEEPS NE ACROSS THE NRN RCKYS. AT THE SFC...SE KS SFC LOW SHOULD
SLOWLY FILL AS IT MOVES INTO WRN MO LATER TODAY AND TO NEAR STL
EARLY FRI. WEAK WARM FRONT EXTENDING SE FROM THE LOW WILL ADVANCE
NE ACROSS THE TN VLY...WHILE TRAILING COLD FRONT SETTLES SLOWLY SE
ACROSS ERN OK/WRN AR AND CNTRL/ERN TX.
...CNTRL/E TX INTO THE LWR MS/LWR TN VLYS THIS AFTN AND EVE...
COLD FRONT IN CNTRL TX...AND COMPOSITE OUTFLOW BOUNDARY ARCING FROM
NE TX ACROSS NRN LA INTO ERN AR WILL BE THE MAIN FOCUS FOR DIURNALLY
ENHANCED STORMS TODAY. OTHER STORMS MAY CONCENTRATE A BIT FARTHER E
ALONG WARM FRONTAL SEGMENT IN ERN MS/WRN AR AND WRN TN/WRN KY.
SATELLITE AND RAOB DATA SHOW A LOW AMPLITUDE DISTURBANCE...NOW OVER
ERN OK/NE TX...ROTATING EWD AROUND BASE OF KS UPR LOW. THE
DISTURBANCE SHOULD CONTINUE ENE THROUGH THE DAY...FURTHERING LOW LVL
DIURNAL DESTABILIZATION AND ASCENT IN LA/MS/TN/KY. COMBINATION OF
RELATIVELY COOL TEMPS ALOFT WITH STG SFC HEATING SHOULD YIELD SBCAPE
OF 2500-3500 J/KG AHEAD OF FRONT/OUTFLOW BOUNDARY FROM CNTRL TX ENE
INTO CNTRL/NRN MS. COUPLED WITH 40-50KT DEEP WLY SHEAR...EXPECT
THAT SFC-BASED STORMS LIKELY TO FORM OVER THE REGION WILL QUICKLY
BECOME SVR...WITH LARGE HAIL THE MAIN THREAT FROM BOTH SUPERCELLS
AND SUSTAINED MULTICELLS. AND...GIVEN RICH MOISTURE SUPPLY AND
STEEP LOW LVL LAPSE RATES...ISOLD TORNADOES WILL ALSO BE A
POSSIBILITY. A TORNADO OR TWO ALSO CANNOT BE RULES OUT FARTHER N/NE
INTO WRN TN AND WRN KY...WHERE BACKED LOW LVL FLOW WILL EXIST INVOF
WARM FRONT.
WHILE MOST OF THE SVR THREAT SHOULD DIMINISH WITH SUNSET...ISOLD SVR
STORMS MAY PERSIST INTO THE NIGHT FROM E TX INTO CNTRL MS.
...ERN KS/WRN MO THIS AFTN...
WILL MAINTAIN LOW PROBABILITIES FOR BOTH HAIL AND BRIEF TORNADOES IN
THIS REGION AS UPR LOW MOVES IN TANDEM WITH SFC LOW. GIVEN
SUFFICIENT SFC HEATING...COOLING/ASCENT WITH UPR SYSTEM AND LOW LVL
CONVERGENCE ALONG ASSOCIATED COLD FRONT AND/OR SFC TROUGH EXTENDING
NE INTO MO SHOULD BE SUFFICIENT FOR SCTD DIURNAL STORMS. BACKED LOW
LVL FLOW MAY YIELD A LOW TORNADO THREAT...BUT CLOUDINESS LIKELY WILL
LIMIT OVERALL SVR POTENTIAL.
...ERN MT THIS AFTN AND EVE...
SCTD TSTMS SHOULD FORM THIS AFTN ALONG LEE TROUGH IN ERN MT...WHERE
HEATING WILL BOOST SBCAPE TO AROUND 500 J/KG. OTHER STORMS MAY FORM
ALONG/AHEAD OF COLD FRONT ASSOCIATED WITH PREVIOUSLY MENTIONED UPR
TROUGH. ALTHOUGH INSTABILITY WILL REMAIN MODEST...COMBINATION OF
STEEP LOW LVL LAPSE RATES... STRENGTHENING/LARGELY UNIDIRECTIONAL
WIND FIELD...AND ASCENT WITH TROUGH SUGGEST THE POTENTIAL FOR ISOLD
STG WIND GUSTS AND/OR MARGINALLY SVR HAIL.
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