SWODY1
SPC AC 141232
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0732 AM CDT THU APR 14 2011
VALID 141300Z - 151200Z
...THERE IS A MDT RISK OF SVR TSTMS FROM SERN KS AND FAR SWRN MO
THROUGH ERN OK INTO WRN AR AND EXTREME NERN TX...
...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE CNTRL AND
SRN PLAINS INTO THE LOWER MS VALLEY REGION...
...SYNOPSIS...
MORNING SATELLITE IMAGERY DEPICTS AN UPPER-LEVEL DISTURBANCE EXITING
EWD FROM THE FOUR CORNERS AREA AND APPROACHING THE SRN ROCKIES. THIS
FEATURE WILL EVENTUALLY MOVE INTO THE CNTRL/SRN PLAINS LATER THIS
AFTERNOON...BEFORE ITS DOWNSTREAM PROGRESS SLOWS AS IT BECOMES A
CLOSED LOW. AN INTENSE MID AND UPPER-LEVEL JET WILL BEGIN TO ROUND
THE BASE OF THE UPPER TROUGH OVER THE SRN HIGH PLAINS DURING THE
AFTERNOON...AND THEN SPREAD DOWNSTREAM ACROSS THE LOWER MS VALLEY
TONIGHT. AS THIS TAKES PLACE...INCIPIENT SURFACE CYCLONE INITIALLY
LOCATED OVER THE TX PANHANDLE WILL ADVANCE NEWD ACROSS OK AND THEN
OCCLUDE OVER KS. A DRYLINE WILL SHARPEN OVER CNTRL OK AS THE SURFACE
LOW MOVES INTO KS...WHILE A COLD FRONT INITIALLY TRAILING SWWD
ACROSS THE SRN HIGH PLAINS ACCELERATES EWD ACROSS THE OZARKS BY
15/12Z.
...ERN KS/OK THROUGH THE LOWER MS VALLEY REGION...
SURFACE OBSERVATIONS AT 12Z INDICATE MOIST TONGUE OF AIR CONTINUES
TO ADVECT NWD ACROSS ERN TX...WITH DEWPOINTS NEAR 60 F OVER N-CNTRL
TX TO UPPER 60S ALONG THE TX GULF COAST. BY MID
AFTERNOON...STRENGTHENING LOW-LEVEL SLY FLOW WILL AID IN NWD
MOISTURE TRANSPORT INTO THE CNTRL PLAINS...WITH MOIST AXIS BECOMING
POSITIONED ADJACENT TO THE SURFACE OCCLUSION OVER CNTRL KS /WHERE
MID TO UPPER 50S DEWPOINTS ARE EXPECTED/ SWD ALONG AND AHEAD OF THE
DRYLINE OVER CNTRL/ERN OK /LOW 60S DEWPOINTS/ AND N-NCNTRL/NERN TX
/MID 60S DEWPOINTS/. MEANWHILE...12Z RAOBS INDICATE STEEP MIDLEVEL
LAPSE RATES ARE PRESENT ACROSS THE REGION /AOA 7.5 C PER KM IN THE
700-500 MB LAYER/...WHICH WILL CONTRIBUTE TOWARD THE DEVELOPMENT OF
WEAK TO MODERATE INSTABILITY COINCIDENT WITH THE MOIST AXIS. MLCAPE
VALUES ARE FORECAST TO RANGE FROM 500-1000 J/KG NEAR THE SURFACE LOW
OVER KS...TO 1000-2500 J/KG NEAR THE DRYLINE OVER OK AND TX.
COMBINATION OF STRONG UPPER-LEVEL DIVERGENCE/LARGE-SCALE ASCENT AND
LOW-LEVEL CONVERGENCE...ALONG WITH AXIS OF STEEP LOW-LEVEL LAPSE
RATES DEVELOPING NWD THROUGH SRN KS...WILL AID IN INITIAL AREA OF
SURFACE BASED THUNDERSTORM DEVELOPMENT DURING EARLY TO MID AFTERNOON
INVOF THE CNTRL KS SURFACE LOW. MODEL FORECAST SOUNDINGS FOR AREAS N
OF THE SURFACE LOW APPEAR SOMEWHAT DRY IN THE BOUNDARY LAYER...WHICH
MAY LIMIT THE SEVERE THREAT DESPITE FAVORABLE SHEAR PROFILES FOR
ROTATING STORMS. ADDITIONAL THUNDERSTORM DEVELOPMENT IS EXPECTED TO
OCCUR S-SEWD FROM THE SURFACE LOW OVER S-CNTRL/SERN KS DURING THE
MID TO LATE AFTERNOON. STEEP MIDLEVEL LAPSE RATES AND SUFFICIENT
VERTICAL WIND SHEAR PROFILES WILL BE IN PLACE FOR SUPERCELL
DEVELOPMENT POSING A THREAT OF LARGE HAIL AND TORNADOES. DUE TO THE
INCREASINGLY NARROW WIDTH OF THE UNSTABLE WARM SECTOR AS THE SURFACE
LOW OCCLUDES...IT IS SOMEWHAT UNCERTAIN HOW FAR DOWNSTREAM THE
SEVERE THREAT WILL EXIST OVER ERN KS AND WRN MO.
FARTHER S OVER CNTRL/ERN OK AND NERN TX...MAJORITY OF MODEL GUIDANCE
INDICATES DISCRETE THUNDERSTORM DEVELOPMENT WILL TAKE PLACE BY LATE
AFTERNOON/EARLY EVENING BENEATH STRONGLY DIFFLUENT UPPER JET
SPREADING ACROSS THE DRYLINE. FAVORABLE INSTABILITY COMBINED WITH
STRONG DEEP LAYER VERTICAL WIND SHEAR /NEAR 70 KT IN THE 0-8 KM
LAYER/ WILL FAVOR A FEW LONGER-LIVED SUPERCELLS WITH A THREAT FOR
VERY LARGE HAIL. LOW-LEVEL HODOGRAPH STRUCTURE IS ALSO FORECAST TO
ENLARGE BY EVENING...WITH EFFECTIVE SRH VALUES INCREASING TO 200-400
M2 S-2. THIS WILL FAVOR THE DEVELOPMENT OF TORNADIC
SUPERCELLS...WITH A STRONG TORNADO NOT OUT OF THE QUESTION. BETWEEN
15/00Z-15/12Z...SURFACE COLD FRONT IS FORECAST TO RAPIDLY MOVE
ACROSS ERN OK INTO WRN AR. STRENGTHENING LOW-LEVEL LINEAR FORCING
FOR ASCENT IS EXPECTED TO AID IN UPSCALE GROWTH TO A QLCS STRUCTURE.
THIS ACTIVITY WILL LIKELY MOVE ACROSS AR AND SRN MO
OVERNIGHT...POSING A THREAT FOR DAMAGING WINDS.
..GARNER/HART.. 04/14/2011
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