SWODY1
SPC AC 121930
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 PM CDT WED OCT 12 2011
VALID 122000Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS THERE IS A SLGT RISK OF SVR
TSTMS THIS AFTERNOON AND EVENING OVER PARTS OF ERN KS...NERN
OK...WRN MO...AND NWRN AR...
...THERE IS A SLGT RISK OF SVR TSTMS THERE IS A SLGT RISK OF SVR
TSTMS THIS AFTERNOON AND EVENING FROM PARTS OF ERN TX INTO WRN MS...
...20Z OUTLOOK UPDATE...
SEVERE POTENTIAL STILL APPEARS GENERALLY LOW TO NEGLIGIBLE ACROSS
MOST AREAS LATE THIS AFTERNOON AND EVENING. IT IS DEBATABLE
WHETHER SLIGHT RISK PROBABILITIES ACROSS EASTERN PORTIONS OF THE
CENTRAL/SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY ARE STILL
JUSTIFIED DUE TO THE GENERALLY MARGINAL NATURE OF THE THREAT AND THE
LIMITED ANTICIPATED COVERAGE OF POSSIBLE STORM REPORTS. BUT THE
1630Z IS BEING MAINTAINED...AS DISCUSSED BELOW.
..KERR.. 10/12/2011
.PREV DISCUSSION... /ISSUED 1126 AM CDT WED OCT 12 2011/
...ARKLATEX/LOWER MS VALLEY NWD INTO THE OZARKS...
HEIGHT FALLS WITHIN EXIT REGION OF STRONG MID- TO UPPER-LEVEL JET
STREAK OVER THE CNTRL/SRN PLAINS WILL CONTRIBUTE TO AMPLIFICATION OF
NEGATIVELY TILTED...FULL-LATITUDE TROUGH TRANSLATING INTO THE MS
VALLEY. AN ASSOCIATED COLD FRONT OVER THE GREAT PLAINS WILL
ACCORDINGLY ADVANCE EWD INTO THE MS VALLEY BY TONIGHT.
COUPLING OF DCVA ATTENDANT TO MIDLEVEL TROUGH AND LOW-LEVEL UPLIFT
ALONG SYNOPTIC COLD FRONT AND RESIDUAL OUTFLOW BOUNDARIES WILL
FOSTER AN INCREASE IN STORM COVERAGE AND INTENSITY TODAY ACROSS THE
REGION WITH ISOLATED OCCURRENCES OF HAIL AND LOCALLY STRONG WIND
GUSTS POSSIBLE. WITHIN THIS BROADER-SCALE REGIME...TWO REGIONS MAY
HAVE A COMPARATIVELY HIGHER RISK FOR SEVERE STORMS. THE FIRST AREA
IS AHEAD OF THE COLD FRONT OVER ERN KS AND NERN OK INTO WRN MO AND
NWRN AR. HERE...RESIDUAL BOUNDARY LAYER DEWPOINTS IN THE UPPER
50S-LOWER 60S WILL ALIGN WITH STRONGER DIABATIC HEATING ALONG WRN
EDGE OF CLOUD SHIELD AND STEADILY COOLING MIDLEVEL TEMPERATURES TO
YIELD MLCAPE VALUES APPROACHING 1000 J/KG. WHILE DEEP-LAYER FLOW
FIELD AND RESULTING VERTICAL SHEAR WILL REMAIN MARGINALLY SUPPORTIVE
OF STORM ORGANIZATION...STEEPENING MIDLEVEL LAPSE RATES AND
RELATIVELY COOL THERMODYNAMIC PROFILES WILL BE FAVORABLE FOR SEVERE
HAIL PRODUCTION WITH THE MOST INTENSE STORMS THIS AFTERNOON AND
EVENING.
THE SECOND AREA OF GREATER SEVERE WEATHER POTENTIAL MAY DEVELOP FROM
PORTIONS OF ERN TX EWD THROUGH NRN/CNTRL LA INTO WRN MS. HERE...THE
RE-DEVELOPMENT OF DIURNALLY ENHANCED STORMS IS ANTICIPATED ALONG
LEADING EDGE OF RESIDUAL COLD POOL ASSOCIATED WITH NOCTURNAL STORM
ACTIVITY. WHILE MIDLEVEL LAPSE RATES WILL NOT BE AS STEEP AS POINTS
TO THE N...THE BOUNDARY LAYER WILL BE MORE MOIST AND VERTICAL SHEAR
WILL BE ENHANCED BY EXIT REGION OF MIDLEVEL JET STREAK DIGGING SEWD.
AS SUCH...THE POTENTIAL WILL EXIST FOR SUPERCELL AND BOWING
STRUCTURES CAPABLE OF MAINLY DAMAGING WIND GUSTS.
...ERN NC INTO THE TIDEWATER...
WATER VAPOR IMAGERY SHOWS A WEAKENING VORTICITY MAXIMUM LIFTING NEWD
ACROSS THE REGION IN RESPONSE TO APPROACH OF UPSTREAM SYSTEM OVER
THE GREAT PLAINS. FORCING FOR ASCENT IN ADVANCE OF THIS FEATURE IS
SUPPORTING AN INCREASE IN TSTMS OVER ERN NC WITHIN A MOIST AND
WEAKLY CAPPED AIR MASS WITH MLCAPE VALUES OF 1000-2000 J/KG. 12Z
OBSERVED SOUNDINGS AND CURRENT VAD DATA INDICATE THAT DEEP-LAYER
WIND FIELD IS MARGINALLY SUPPORTIVE OF STORM ORGANIZATION/ROTATION
WITH EFFECTIVE BULK SHEAR VALUES AROUND 30 KT. HOWEVER...ELY
LOW-LEVEL FLOW IN ADVANCE OF WEAK SURFACE LOW DEVELOPING NWD WILL
MAINTAIN A CORRIDOR OF MODEST LOW-LEVEL SHEAR WHICH MAY PROMOTE SOME
STORM ROTATION AND A LOW PROBABILITY RISK FOR DAMAGING WINDS AND
PERHAPS A BRIEF TORNADO.
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