SWODY1
SPC AC 202000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT FRI MAY 20 2011
VALID 202000Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM NERN TX TO THE MO
BOOTHEEL/WRN KY AND WRN TN...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN AND
CNTRL PLAINS...
...ARKLATEX TO MO BOOTHEEL/WRN TN...
ADJUSTED SLGT RISK AND RAISED HAIL AND WIND PROBABILITIES ACROSS
THESES AREAS BASED ON LATEST TRENDS. SURFACE AND UA ANALYSIS REVEALS
PRIMARILY TWO AREAS WITHIN THIS BROADER ZONE WHERE SEVERE STORMS
WILL BE MOST LIKELY THIS AFTERNOON AND EVENING. IN BETWEEN THE TWO
AREAS...GENERALLY FROM ERN OK ACROSS THE OZARKS...EXISTS A LARGE
COLD POOL WHERE AIRMASS HAS BEEN CONVECTIVELY OVERTURNED.
AREA 1) ACROSS NERN/ERN TX TO SRN AR AND NWRN LA. AIRMASS HERE HAS
BECOME STRONGLY UNSTABLE AND WEAKLY CAPPED AND WOULD EXPECT TO
CONTINUE TO SEE VERY INTENSE CONVECTION SPREAD GRADUALLY
EAST/NORTHEAST ACROSS THE REGION THROUGH THIS EVENING. MARGINAL DEEP
LAYER SHEAR ACROSS MUCH OF THE AREA SOUTH OF WELL-DEFINED OUTFLOW
BOUNDARY WILL LIKELY SUPPORT MULTICELLULAR STORMS WITH SOME THREAT
FOR WIND AND HAIL. GREATER STORM ORGANIZATION AND A POSSIBLE TORNADO
OR TWO MAY OCCUR ALONG THE OUTFLOW BOUNDARY WHERE BOTH DEEP LAYER
AND LOW LEVEL SHEAR WILL BE STRONGEST.
AREA 2) NERN AR ACROSS MO BOOTHEEL AND WRN KY/TN. LEADING EDGE OF
STRONGER CONVECTION WILL SPREAD INTO VERY WARM AIRMASS WHERE DCAPE
VALUES IN EXCESS OF 1000 J PER KG SHOULD RESULT IN AN ENHANCED WIND
THREAT THIS AFTERNOON. THIS POTENTIAL CURRENTLY EXISTS OVER A
RELATIVELY SMALL AREA AND THERE IS SOME UNCERTAINTY ABOUT THE EWD
EXTENT OF THE THREAT ACROSS THE MS RIVER. HOWEVER...LATEST RADAR
TRENDS SUGGEST AN INCREASE IN SEVERE WIND PROBABILITIES IN THIS AREA
IS WARRANTED.
...SRN/CNTRL PLAINS...
TSTMS ARE CURRENTLY DEVELOPING ALONG A COLD FRONT WHICH STRETCHES
FROM CNTRL NEB SWD INTO WRN OK. FORCING FOR ASCENT ATTENDANT TO
VORTICITY MAXIMUM PIVOTING NNEWD ACROSS THE REGION SHOULD SUPPORT AN
INCREASE IN STORM COVERAGE AND INTENSITY THROUGH THE REMAINDER OF
THE AFTERNOON. AMBIENT WARM SECTOR AIR MASS IS CHARACTERIZED BY A
GRADUALLY WARMING BOUNDARY LAYER WITH DEWPOINTS IN THE UPPER 50S TO
LOWER 60S...RESULTING IN MLCAPE VALUES OF 500-1000 J/KG. GIVEN THE
SUPERPOSITION OF MID AND UPPER-LEVEL JET AXES ALONG INSTABILITY
AXIS...SETUP WILL CONTINUE TO FAVOR THE DEVELOPMENT OF ORGANIZED
STORMS...INCLUDING SUPERCELLS AND LINE SEGMENTS CAPABLE OF HAIL AND
LOCALLY DAMAGING WIND GUSTS.
..CARBIN.. 05/20/2011
.PREV DISCUSSION... /ISSUED 1128 AM CDT FRI MAY 20 2011/
...ERN PARTS OF OK/TX INTO AR/NRN LA...
SRN EXTENSION OF NOCTURNAL QLCS IS EXPECTED TO PERSIST
TODAY...GRADUALLY MOVING/DEVELOPING EWD WITH TIME. THE INFLUX OF A
SEASONABLY MOIST AIR MASS /CHARACTERIZED BY BOUNDARY LAYER DEWPOINTS
IN UPPER 60S TO LOWER 70S/ WILL BE MAINTAINED BY A 35-45 KT SLY LLJ
WHICH SHOULD SERVE TO ENHANCE UPDRAFT STRENGTH ALONG LEADING EDGE OF
SYSTEM COLD POOL. ADDITIONAL MORE DISCRETE STORM DEVELOPMENT WILL
REMAIN POSSIBLE IN ADVANCE OF QLCS AND S OF WARM FRONT LIFTING NWD
INTO SRN MO WHERE LOW-LEVEL SHEAR WILL BE ENHANCED BY THE PRESENCE
OF THE LLJ. WHILE MID AND HIGH-LEVEL WIND FIELD WILL NOT BE
PARTICULARLY STRONG...THE PRESENCE OF 0-1 KM SRH OF 200-250 M2/S2
AND THE MOIST BOUNDARY LAYER SUGGEST A RISK FOR A FEW TORNADOES WITH
ANY SUPERCELLS THAT CAN BECOME ESTABLISHED. OTHERWISE...EXPECT
LARGER-SCALE CONVECTIVE SYSTEM TO REMAIN CAPABLE OF DAMAGING WIND
GUSTS AND HAIL TODAY INTO THIS EVENING.
FOR ADDITIONAL NEAR TERM GUIDANCE...SEE MCD 825.
...CNTRL/ERN NEB INTO WRN OK...
LATEST MODEL GUIDANCE SUGGESTS THAT BREAKS IN THE CLOUDS COUPLED
WITH HEIGHT FALLS/DYNAMIC COOLING IN THE MIDLEVELS ASSOCIATED WITH
VORTICITY MAXIMUM PIVOTING NNEWD THROUGH THE HIGH PLAINS MAY SUPPORT
A NARROW AXIS OF MODERATE INSTABILITY BY AFTERNOON IMMEDIATELY AHEAD
OF PACIFIC FRONT. THE STRONGEST DEEP-LAYER VERTICAL SHEAR /40-50
KT/ WILL RESIDE ACROSS OK INTO SRN KS...DECREASING TO 30-35 KT IN
NEB. AS SUCH...ISOLATED TO WIDELY SCATTERED STORMS /INCLUDING
SUPERCELLS/ WILL BE POSSIBLE THIS AFTERNOON INTO EVENING WITH THE
PRIMARY HAZARD BEING LARGE HAIL.
...NRN PLAINS...
AS MIDLEVEL DRY SLOT CONTINUES TO DEVELOP NWD TODAY...SOME POTENTIAL
FOR CLEARING WILL EXIST ALONG IMMEDIATE FRONT ARCING NWWD FROM CNTRL
NEB TO WEAK LOW PRESSURE OVER WRN SD. GIVEN VERTICALLY VEERING
WINDS WITH HEIGHT...BOUNDARY LAYER DEWPOINTS IN THE 50S AND A
RELATIVELY COOL THERMODYNAMIC PROFILE PER 12Z RAP SOUNDING...A RISK
FOR ISOLATED SEVERE STORMS WILL EXIST SHOULD SUFFICIENT
HEATING/DESTABILIZATION OCCUR. DUE TO UNCERTAINTY IN THE DEGREE OF
INSTABILITY THAT WILL DEVELOP LATER TODAY...LOW SEVERE WEATHER
PROBABILITIES WILL BE MAINTAINED.
...ERN CAROLINAS...
VORTICITY MAXIMUM OVER WV/VA LATE THIS MORNING WILL CONTINUE SEWD
TODAY...GLANCING THE REGION WITH WEAK HEIGHT FALLS/FORCING FOR
ASCENT. THIS MIDLEVEL SYSTEM WILL BE ATTENDED BY A WEAK SURFACE
TROUGH/COLD FRONT WHICH MAY SERVE AS THE FOCUS FOR ISOLATED TO
WIDELY SCATTERED TSTM DEVELOPMENT THIS AFTERNOON. DAYTIME HEATING
COUPLED WITH MODEST BOUNDARY LAYER MOISTURE CONTENT MAY YIELD MLCAPE
VALUES APPROACHING 500-1000 J/KG AHEAD OF FRONT. GIVEN MODESTLY
STRONG MID AND HIGH-LEVEL WNWLY FLOW OBSERVED BY 12Z SOUNDINGS...
SOME RISK FOR LOCALLY STRONG WIND GUSTS AND PERHAPS HAIL WILL EXIST
WITH ANY STORMS THAT CAN DEVELOP.
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