NWS STORM PREDICTION CENTER NORMAN OK
0744 AM CDT SAT MAY 02 2009
VALID 021300Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLAINS EWD ACROSS
THE TN/MS VALLEYS INTO THE CAROLINAS/SRN VA...
..SYNOPSIS...
SPLIT UPPER FLOW PATTERN WILL REMAIN OVER THE CONUS TODAY...WITH A
DEEP TROUGH LOCATED OVER ERN CANADA/NERN STATES AND SRN STREAM
STRETCHING E-W ACROSS THE SRN PORTIONS OF THE COUNTRY. A RELATIVELY
STRONG SHORTWAVE TROUGH...EMBEDDED WITHIN THE SRN STREAM...WILL
SHIFT EWD FROM NM INTO CENTRAL OK/TX BY LATE AFTERNOON...AND INTO AR
OVERNIGHT. AT THE SURFACE...A COLD FRONT WILL SINK SLOWLY SEWD FROM
THE MID ATLANTIC STATES AND EXTEND WWD INTO THE TN VALLEY.
HOWEVER...THE WRN PORTION OF THE FRONT FROM AR SWWD INTO SWRN TX
WILL MOVE LITTLE TODAY...BUT WILL BEGIN SHIFTING SWD OVERNIGHT AS
THE UPPER WAVE PASSES.
...SRN PLAINS/LOWER MS VALLEY...
BROAD LOW LEVEL JET ABOVE SHALLOW COLD FRONT AND APPROACHING UPPER
TROUGH WILL RESULT IN BANDS OF ELEVATED CONVECTION TO SHIFT EWD
ACROSS OK/AR. EFFECTIVE SHEAR AT 30-40 KT AND MUCAPES BETWEEN 1000
AND 2000 J/KG SHOULD BE SUFFICIENT FOR SOME SEVERE HAIL...
ESPECIALLY ACROSS THE SERN HALF OF OK AND CENTRAL/NRN AR.
THE LARGE SCALE LIFT ASSOCIATED WITH UPPER WAVE AND HIGH LEVEL
DIFFLUENT FLOW IS FORECAST TO SPREAD INTO NRN/CENTRAL TX BETWEEN 18Z
AND 21Z...AND AID CONVECTIVE INITIATION IN THE WARM SECTOR.
EFFECTIVE SHEAR WILL BE STRONGER TODAY...AROUND 50 KT...THAN ON
FRIDAY AS AN ASSOCIATED 50-60 KT JET MAX SPREADS INTO THE REGION.
ALONG WITH THE POTENTIAL FOR LARGE HAIL...WIND DAMAGE AND A FEW
TORNADOES ARE ALSO LIKELY...GIVEN THAT SURFACE DEWPOINTS NEAR 70F
WILL YIELD MLCAPES BETWEEN 1500-2500 J/KG. THE HIGHEST POTENTIAL FOR
TORNADOES IS EXPECTED ACROSS NRN TX WHERE THE STRONGEST
FORCING...LOW/HIGH LEVEL SHEAR AND STRONGER THUNDERSTORM DEVELOPMENT
IS LIKELY DURING THE AFTERNOON HOURS. AS THE UPPER TROUGH AND
FORCING SHIFTS EWD...THE STORMS MAY CONSOLIDATE INTO A LINEAR SYSTEM
AND MOVE EWD INTO SRN AR/NRN LA...WITH WIND DAMAGE THEN BECOMING THE
PRIMARY THREAT.
STORMS ARE EXPECTED TO INITIATE ACROSS THE MOUNTAINS OF NERN MEXICO
AND THE RIO GRANDE VALLEY LATE THIS AFTERNOON AS SRN TAIL OF NRN TX
SHORTWAVE TROUGH BRUSHES AREA. THOUGH A STRONGER CAP SHOULD RESULT
IN LESS STORM COVERAGE THAN ACROSS NRN TX...MLCAPES NEAR 3000 J/KG
AND 40-50 KT WLY MID LEVEL WINDS SHOULD SUPPORT A THREAT FOR SEVERE
WINDS/HAIL DURING THE LATE AFTERNOON/EVENING HOURS.
...TN VLY TO VA/CAROLINAS...
BANDS OF CONVECTION EXTENDED FROM CENTRAL AR EWD INTO NRN AL/ERN TN
THIS MORNING. EMBEDDED MCV/S ARE LIKELY TO BECOME MORE EVIDENT
DURING THE DAY AND AID IN THE ORGANIZATION OF NEW AND/OR INTENSIFIED
CONVECTION THIS AFTERNOON. WSWLY MID LEVEL WINDS AT 30 KT AND
ENHANCED FLOW ASSOCIATED WITH THE MCV/S FAVOR FORWARD PROPAGATING
BOWS WITH DAMAGING WINDS. DESPITE DEWPOINTS IN THE MID 60S...WEAK
MID LEVEL LAPSE RATES WILL ONLY RESULT IN MLCAPES AROUND 1000 J/KG.
ONLY MARGINALLY SEVERE HAIL IS EXPECTED GIVEN THE WEAK DYNAMICAL
FORCING/INSTABILITY. WITH LOSS OF DIURNAL HEATING...STORMS SHOULD
WEAKEN BELOW SEVERE CRITERIA.
..IMY/GARNER.. 05/02/2009
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