SWODY1
SPC AC 211247
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0747 AM CDT MON APR 21 2008
VALID 211300Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF OK...KS...AND
MO...
A LARGE UPPER TROUGH IS PRESENT TODAY OVER THE WESTERN STATES...
WITH SEVERAL SMALLER-SCALE FEATURES ROTATING THROUGH BASE OF TROUGH
INTO THE SOUTHERN/CENTRAL ROCKIES. ONE SUCH FEATURE IS CURRENTLY
ROTATING ACROSS THE SOUTHERN ROCKIES AND WILL MOVE INTO WEST TX/OK
AND PARTS OF KS LATER TODAY AND TONIGHT. LOW LEVEL MOISTURE IS
RAPIDLY RETURNING NORTHWARD ACROSS THE PLAINS...WHILE A COLD FRONT
SURGES SOUTHWARD ACROSS WESTERN KS AND THE TX/OK PANHANDLE. DESPITE
SEVERAL FAVORABLE PARAMETERS FOR SEVERE STORM DEVELOPMENT THIS
EVENING OVER KS/OK/TX...A STRONG CAPPING INVERSION RESULTS IN A
HIGHLY CONDITIONAL SEVERE OUTLOOK TODAY OVER PARTS OF KS/OK.
...OK...
MORNING SOUNDINGS AT OUN/FWD SHOW A PRONOUNCED CAP THAT IS LIKELY TO
BE MAINTAINED THROUGH TODAY/TONIGHT. MEANWHILE...LIMITED VERTICAL
MIXING MAY HELP DEWPOINTS POOL WELL INTO THE 60S ACROSS PARTS OF OK.
THIS WILL YIELD AFTERNOON MLCAPE VALUES OF 3500+ J/KG. PRESENT
INDICATIONS ARE THAT COLD FRONT/DRYLINE TRIPLE POINT WILL DEVELOP
OVER NORTHWEST OK AND WILL BE THE MOST LIKELY INITIATION POINT FOR
THUNDERSTORMS BY EARLY EVENING. NAM AND EXPERIMENTAL MESOSCALE
NMM/ARW SOLUTIONS SHOW VERY ISOLATED BUT INTENSE THUNDERSTORM
ACTIVITY IN THIS AREA. MEANWHILE...ECMWF/GFS SOLUTIONS INDICATE CAP
WILL REMAIN TOO STRONG AND NO CONVECTION DEVELOPS IN OK. THESE
DIFFERENCES IN MODEL GUIDANCE AND NOTED STRENGTH OF CAP ON MORNING
SOUNDINGS PROVIDE CONSIDERABLE UNCERTAINTY IN THIS OUTLOOK. IF
ISOLATED STORMS CAN DEVELOP NEAR THE TRIPLE POINT...VERTICAL SHEAR
AND CAPE PROFILES ARE CERTAINLY FAVORABLE FOR SUPERCELL STORMS
CAPABLE OF VERY LARGE HAIL AND ISOLATED TORNADOES.
...KS/MO/AR...
FARTHER NORTH...CONVECTIVE INITIATION APPEARS MORE LIKELY FROM SOUTH
CENTRAL KS INTO NORTHWEST MO BY LATE THIS AFTERNOON AND EVENING AS
UPPER FEATURE APPROACHES. INSTABILITY PARAMETERS WILL BE SOMEWHAT
WEAKER THAN IN OK...BUT WILL STILL BE SUFFICIENT FOR STRONG/SEVERE
STORMS CAPABLE OF LARGE HAIL AND DAMAGING WINDS. THESE STORMS MAY
PERSIST WELL INTO THE NIGHT AND DEVELOP SOUTHEASTWARD INTO AR AS
STRONG THERMAL/MOISTURE ADVECTION OCCURS.
...UPPER MS VALLEY...
MODELS SUGGEST FORCING FOR ASCENT ATTENDANT TO A LEAD MID LEVEL
IMPULSE SPREADING ENEWD ACROSS THIS REGION TODAY COMBINED WITH
FRONTAL CIRCULATION ALONG COLD FRONT SHOULD SUPPORT TSTMS SPREADING
EWD THROUGH ERN DAKOTAS/MN TO WRN WI/WRN U.P. OF MI. EFFECTIVE BULK
SHEAR OF 25-30 KT MAY SUPPORT A FEW ORGANIZED STORMS...BUT WEAK
INSTABILITY IS EXPECTED TO LIMIT THE SEVERE WEATHER THREAT. STORMS
SHOULD BECOME UNDERCUT AS THE COLD FRONT SPREADS EWD...WITH ISOLATED
HAIL BEING THE PRIMARY THREAT.
...ERN NC...
CLOSED UPPER LOW LOCATED OVER CENTRAL NC AT 12Z TODAY IS EXPECTED TO
WEAKEN AS IT TRACKS SEWD TO OFF THE NC/SC COAST BY MID-LATE THIS
EVENING. RESIDUAL SURFACE MOISTURE /DEWPOINTS IN THE MID 50S/
COMBINED WITH SURFACE HEATING BENEATH COLD MID LEVEL TEMPERATURES
/-22 C AT 500 MB/ ARE EXPECTED TO RESULT IN MARGINAL INSTABILITY
/MUCAPE 500-1000 J/KG/ INTO THE AFTERNOON. ALTHOUGH DEEP LAYER
SHEAR WILL BE WEAK ALONG TRACK OF UPPER LOW...STEEP LAPSE RATES/COLD
MID LEVEL TEMPERATURES MAY PROVE SUFFICIENT FOR ISOLATED HAIL/WIND
THREATS WITH STRONGEST STORMS.
..HART/GRAMS.. 04/21/2008
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