SPC AC 180546
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1246 AM CDT SAT APR 18 2009
VALID 181200Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE CNTRL AND SRN
PLAINS INTO SRN LA...
...KS AND OK AND N CNTRL TX...
CLOSED UPPER LOW OVER SERN CO WILL CONTINUE EAST...AND IS FORECAST
TO BE CENTERED OVER EXTREME ERN KS 12Z SUNDAY. SEVERAL VORTICITY
MAXIMA WILL ROTATE THROUGH THIS FEATURE. A COLD FRONT WILL ACCOMPANY
THE UPPER LOW AND INTERCEPT THE DRYLINE SATURDAY EVENING OVER PARTS
OF KS AND OK.
RICHER MOISTURE WITH UPPER 60F TO 70F SURFACE DEWPOINTS WILL REMAIN
SOUTH OF A RESIDUAL OUTFLOW BOUNDARY ACROSS S TX.
HOWEVER...DEWPOINTS IN THE UPPER 40S TO LOW 50S WILL PERSIST EAST OF
DRYLINE ACROSS THE ERN HALF OF OK INTO KS. VERY COLD AIR ALOFT WITH
-18C TO -20C AT 500 MB AND STEEP 700-500 MB LAPSE RATES WILL
COMPENSATE FOR THE MORE LIMITED MOISTURE IN THIS REGION. MLCAPE FROM
500 TO 1000 J/KG WILL BECOME PROBABLE AS THE BOUNDARY LAYER WARMS
DURING THE AFTERNOON. MODELS SUGGEST ANOTHER IN A SERIES OF
VORTICITY MAXIMA WILL ROTATE THROUGH THE UPPER LOW AND AFFECT PARTS
OF KS...OK AND NRN TX. STORMS WILL LIKELY REDEVELOP DURING THE
AFTERNOON AS THE BOUNDARY LAYER DESTABILIZES. LOW LEVEL FLOW WILL
REMAIN WEAK...BUT 40-50 KT MID LEVEL WINDS IN PROXIMITY TO UPPER JET
ROTATING THROUGH UPPER TROUGH WILL MAINTAIN SUFFICIENT BULK SHEAR
FOR SOME STORMS TO DEVELOP SUPERCELL STRUCTURES. LARGE HAIL SHOULD
BE THE PRIMARY THREAT WITH THIS ACTIVITY.
...S CNTRL AND SERN TX THROUGH SRN HALF OF LA...
CONVECTIVE OUTFLOW BOUNDARY REMAINS FROM JUST OFF THE SE TX COAST
WWD THROUGH SRN TX. A RESERVOIR OF STRONG INSTABILITY EXISTS SOUTH
OF THIS BOUNDARY WITH MLCAPE AROUND 2500 J/KG. BROAD ZONE OF MODEST
SLY LOW LEVEL FLOW IS RESULTING IN SUFFICIENT ISENTROPIC LIFT ABOVE
THE OUTFLOW BOUNDARY FOR ELEVATED STORMS TO DEVELOP FROM S THROUGH
SERN TX. LATEST MODEL RUNS INDICATE AN INCREASE IN STORMS EARLY
SATURDAY OVER S CNTRL TX...POSSIBLY IN RESPONSE TO AN INCREASE IN
DEEP LAYER ASCENT ASSOCIATED WITH UPPER JET EXIT REGION ROTATING
THROUGH UPPER TROUGH. STORMS WILL SUBSEQUENTLY DEVELOP NEWD THROUGH
S CNTRL AND SERN TX DURING THE DAY...POSSIBLY GROWING UPSCALE INTO
AN MCS.
EXTENT OF SEVERE THREAT IN THIS REGION IS SOMEWHAT UNCERTAIN AND
WILL DEPEND ON WHETHER THE BOUNDARY LAYER CAN RECOVER INLAND FROM
THE COAST. A MODEST LOW LEVEL JET IS FORECAST TO SHIFT EWD TOWARD
SERN TX AND LA SATURDAY MORNING...AND THIS COULD SUSTAIN
THUNDERSTORM DEVELOPMENT NORTH OF THE OUTFLOW BOUNDARY WHICH WOULD
IN TURN DELAY OR LIMIT INLAND RECOVERY. STORMS ARE EXPECTED TO
INCREASE OVER S CNTRL TX EARLY SATURDAY AND SUBSEQUENTLY MOVE ENEWD
THROUGH SERN TX ALONG INSTABILITY GRADIENT. SUFFICIENT BULK SHEAR
WILL EXIST FOR SOME ORGANIZED STORM STRUCTURES INCLUDING SUPERCELL
AND BOWING SEGMENTS. PRIMARY THREATS WILL BE ISOLATED DAMAGING WIND
AND HAIL. AN ISOLATED TORNADO OR TWO CANNOT BE RULED
OUT...ESPECIALLY FROM SERN TX INTO SRN LA BUT WILL BE CONDITIONAL
UPON INLAND BOUNDARY LAYER RECOVERY.
..DIAL/SMITH.. 04/18/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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