SWODY1
SPC AC 171949
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0249 PM CDT MON MAR 17 2008
VALID 172000Z - 181200Z
..THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF CNTRL AND
SOUTHWEST TX...
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN PLAINS
AND OZARK PLATEAU...
..SRN PLAINS...
WATER VAPOR IMAGERY CURRENTLY SHOWS A STRONG UPPER-LEVEL LOW OVER
THE SOUTHWESTERN STATES AND THE LOW IS FORECAST TO DIG SEWD INTO NRN
MEXICO TONIGHT. THIS WILL RESULT IN INCREASING LARGE-SCALE ASCENT
ACROSS THE SRN PLAINS AND NUMEROUS THUNDERSTORMS SHOULD DEVELOP LATE
THIS AFTERNOON THROUGH THE OVERNIGHT PERIOD. AT THE SFC...A DRYLINE
IS CURRENTLY LOCATED ACROSS WCNTRL TX WITH SFC DEWPOINTS EAST OF THE
DRYLINE AROUND 60 F. STRONG TO SEVERE STORMS ARE ALREADY DEVELOPING
ACROSS SRN OK AND NCNTRL TX AND THIS ACTIVITY SHOULD GRADUALLY
EXPAND IN COVERAGE. IN ADDITION...MOISTURE ADVECTION ON THE WEST
SIDE OF A 50 TO 60 KT LOW-LEVEL JET WILL INCREASE DEWPOINTS INTO THE
LOWER TO MID 60S F ACROSS MUCH OF OK AND WCNTRL TX. ALTHOUGH A
CAPPING INVERSION IS IN PLACE ACROSS MUCH OF CNTRL AND SOUTHWEST
TX...SHORT-TERM MODEL FORECASTS GRADUALLY WEAKEN THE CAP AND DEVELOP
MODERATE INSTABILITY NWD ACROSS THE HILL COUNTRY INTO NORTH TX BY
LATE AFTERNOON. THIS SHOULD ALLOW A LARGE MCS TO ORGANIZE TONIGHT
ACROSS THE WARM SECTOR AS THE UPPER-LEVEL SYSTEM APPROACHES FROM THE
WEST.
CONCERNING THE SHEAR ENVIRONMENT...RUC ANALYSIS SHOWS A 80 TO 90 KT
MID-LEVEL JET OVER NRN MEXICO. THIS FEATURE WILL DRIFT EWD INTO WEST
TX THROUGH THIS EVENING REINFORCING THE STRONG VERTICAL SHEAR
ALREADY IN PLACE. CURRENT RADAR TRENDS SHOW LINEAR ORGANIZATION
OCCURRING ALONG A COLD FRONT IN WRN OK. SUPERCELLS WILL BE POSSIBLE
WITHIN THE CONVECTIVE LINES WITH THE GREATEST POTENTIAL WHERE GAPS
IN THE LINES EXIST. FURTHER SOUTH ACROSS THE MODERATE RISK AREA
WHERE THE EML IS MORE PRONOUNCED...THE POTENTIAL FOR DISCRETE
SUPERCELLS APPEARS HIGHER. IN THIS AREA...LOW-LEVEL SHEAR SHOULD
GRADUALLY INCREASE LATE THIS AFTERNOON INTO THIS EVENING AS A 50 TO
60 KT LOW-LEVEL JET DEVELOPS ACROSS SOUTH TX. THIS SHOULD SUPPORT A
THREAT FOR TORNADOES AS SUPERCELLS MATURE AND MOVE EWD INTO
INCREASING LOW-LEVEL MOISTURE. THE TORNADO THREAT SHOULD BE GREATEST
IN THE 00Z TO 06Z TIME FRAME FROM DEL RIO NNEWD ACROSS THE TX HILL
COUNTRY TO AREAS WEST OF FORT WORTH WHERE AN ISOLATED STRONG TORNADO
OR TWO WILL BE POSSIBLE. A FEW TORNADOES WILL ALSO BE POSSIBLE
ACROSS CNTRL AND ERN OK WHERE STRONG LOW-LEVEL SHEAR IS PRESENT AND
LCL HEIGHTS WILL BE RELATIVELY LOW. IN ADDITION...FORECAST
SOUNDINGS THIS AFTERNOON THROUGH TONIGHT SHOW STEEP MID-LEVEL LAPSE
RATES ACROSS THE SRN PLAINS ASSOCIATED WITH AN ELEVATED MIXED LAYER
SUGGESTING THE SHEAR AND THERMODYNAMIC ENVIRONMENT IS VERY FAVORABLE
FOR SUPERCELLS WITH LARGE HAIL. VERY LARGE HAIL WILL BE POSSIBLE
FROM THE RED RIVER SSWWD TO THE RIO GRAND VALLEY WHERE MODERATE
INSTABILITY SHOULD DEVELOP BY LATE AFTERNOON AND PERSIST THROUGH THE
EVENING. DURING THE OVERNIGHT PERIOD...MODEL FORECASTS SUGGEST A
TRANSITION TO A LINEAR-STRUCTURED MCS SHOULD OCCUR SUGGESTING A MORE
WIDESPREAD WIND DAMAGE THREAT SHOULD DEVELOP ACROSS THE I-35
CORRIDOR IN ECNTRL AND SOUTHWEST TX. THE SEVERE THREAT SHOULD
PERSIST THROUGH LATE IN THE PERIOD DUE TO INCREASING LOW-LEVEL
MOISTURE AND THE RESULTANT MODERATE INSTABILITY.
..OZARK REGION/CNTRL PLAINS...
LOW-LEVEL MOISTURE WILL BEGIN TO INCREASE ACROSS SE KS AND SRN MO
THIS AFTERNOON AS A COLD FRONT ADVANCES SEWD ACROSS THE REGION. IN
ADDITION...MODEL FORECASTS INCREASE LOW-LEVEL CONVERGENCE ALONG THE
BOUNDARY AND THIS SHOULD RESULT IN THE DEVELOPMENT OF SEVERAL
CONVECTIVE LINES THIS EVENING. ALTHOUGH...INSTABILITY WILL BE
SOMEWHAT LIMITED...THE STRONG VERTICAL SHEAR SHOWN BY RUC ANALYSIS
AND COLD TEMPS ALOFT MAY SUPPORT A THREAT FOR HAIL.
.BROYLES.. 03/17/2008
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