SWODY1
SPC AC 231241
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0741 AM CDT WED APR 23 2008
VALID 231300Z - 241200Z
...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING FROM
WESTERN NORTH TX INTO SOUTHERN OK...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE SOUTHERN AND
CENTRAL PLAINS STATES...
MORNING WATER VAPOR LOOPS SHOW A DEEP UPPER LOW OFF THE WA/ORE COAST
WITH A SIGNIFICANT SHORTWAVE TROUGH ROTATING INLAND INTO THE GREAT
BASIN. ANOTHER STRONG FEATURE IS EMBEDDED IN THE SUBTROPICAL JET
OVER NORTHERN MEXICO. THIS IMPULSE IS EXPECTED TO PROVIDE A RATHER
ACTIVE SEVERE WEATHER DAY TO PORTIONS OF THE SOUTHERN AND CENTRAL
PLAINS TODAY/TONIGHT.
...TX/OK/KS TODAY...
LARGE SCALE ASCENT IN ADVANCE OF SOUTHERN STREAM SHORTWAVE TROUGH IS
BEGINNING TO OVERSPREAD WEST TX. INCREASING LOW LEVEL WARM
ADVECTION AND LIFT WILL LIKELY WEAKEN CAPPING INVERSION AND LEAD TO
SCATTERED THUNDERSTORMS BY LATE MORNING FROM THE EASTERN TX
PANHANDLE INTO WESTERN OK. 12Z SOUNDINGS AT AMA/MAF/OUN/DDC SHOW
VERY STEEP MID LEVEL LAPSE RATES AND ABUNDANT CAPE VALUES /700-500MB
LR OF 8-9 C/KM AND MUCAPE OF 2000-4000 J/KG/. VERY FAVORABLE
THERMODYNAMIC PARAMETERS SUGGEST A RISK OF LARGE HAIL AND DAMAGING
WINDS ACROSS THIS AREA THROUGH THE AFTERNOON AND EARLY EVENING.
PLEASE REFER TO SWOMCD NUMBER 696 FOR FURTHER DETAILS.
...TX/OK THIS AFTERNOON AND EVENING...
AFOREMENTIONED THUNDERSTORMS WILL LIKELY LIFT NORTHWARD ACROSS TX
PANHANDLE/WESTERN OK TODAY...LEAVING AREAS FROM WEST CENTRAL TX INTO
SOUTH CENTRAL OK RELATIVELY UNDISTURBED. THIS REGION IS EXPECTED TO
REMAIN COVERED BY DENSE CIRRUS MUCH OF THE DAY...BUT WILL STILL SEE
SOME DAYTIME HEATING/DESTABILIZATION. VERY STEEP MID LEVEL LAPSE
RATES AND DEWPOINT VALUES IN THE UPPER 60S WILL YIELD AFTERNOON
MLCAPE VALUES OF 3000+ J/KG. VERTICAL SHEAR PROFILES WILL BE WEAK
THROUGH EARLY AFTERNOON...BUT SHOULD STRENGTHEN RAPIDLY THROUGH 00Z
AS PROGRESSIVE UPPER TROUGH APPROACHES. INITIAL THUNDERSTORM
DEVELOPMENT IS CURRENTLY ANTICIPATED ALONG WEST EDGE OF INSTABILITY
AXIS AND IN EXIT REGION OF COMPACT UPPER JET...ROUGHLY WEST OF
ABI/SJT. THESE STORMS ARE EXPECTED TO INCREASE IN COVERAGE THROUGH
THE LATE AFTERNOON/EVENING AND TRACK/DEVELOP INTO SOUTHERN OK/NORTH
TX. THERMODYNAMIC AND DEEP LAYER VERTICAL SHEAR PARAMETERS ARE VERY
FAVORABLE FOR SUPERCELLS CAPABLE OF VERY LARGE HAIL. MODEL GUIDANCE
VARIES SIGNIFICANTLY REGARDING LOW LEVEL RESPONSE OF WIND FIELDS TO
APPROACHING TROUGH. HOWEVER...IT APPEARS THAT LOW LEVEL SHEAR WILL
BECOME SUFFICIENT FOR AN INCREASING TORNADO THREAT BY EARLY EVENING
OVER MODERATE RISK AREA. THUNDERSTORMS WILL SPREAD EASTWARD ACROSS
OK WITH A CONTINUED THREAT OF LARGE HAIL AND DAMAGING WINDS WELL
INTO THE NIGHT.
...SD/NEB...
SIGNIFICANT SHORTWAVE TROUGH CURRENTLY OVER UT WILL ROTATE EASTWARD
AND BEGIN TO AFFECT THE CENTRAL/NORTHERN HIGH PLAINS BY EVENING.
STRONG SOUTHERLY LOW LEVEL WINDS OVER THE HIGH PLAINS WILL HELP
TRANSPORT MOISTURE NORTHWARD AND YIELD AFTERNOON MLCAPE VALUES OF
500+ J/KG OVER WESTERN NEB/SD. MODEL GUIDANCE IS CONSISTENT IN
DEVELOPING SCATTERED THUNDERSTORMS ALONG THE WY BORDER WHICH WILL
SPREAD ACROSS SLIGHT RISK AREA. FORECAST SOUNDINGS SHOW VERY STEEP
LOW/MID LEVEL LAPSE RATES AND SUFFICIENT VERTICAL SHEAR FOR A RISK
OF HIGH-BASED SUPERCELLS CAPABLE OF LARGE HAIL. THESE STORMS WILL
LIKELY WEAKEN DURING THE EVENING AS DIURNAL COOLING OCCURS.
..HART/JEWELL.. 04/23/2008
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