[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 250559
SWODY1
SPC AC 250557

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT TUE APR 25 2006

VALID 251200Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
PLAINS...LOWER MS VALLEY...TN VALLEY AND CAROLINAS...

...LOWER MS VALLEY/SRN PLAINS...
AT UPPER-LEVELS...A FLAT RIDGE OVER THE MS VALLEY EARLY IN THE
PERIOD WILL WEAKEN AS A BROAD TROUGH DEVELOPS ACROSS THE PLAINS AND
MOVES TOWARD THE MS VALLEY. AT THE SFC...A COLD FRONT WILL MOVE SEWD
ACROSS THE SRN PLAINS/OZARKS AND A LINEAR MCS MAY BE ONGOING ALONG
AND AHEAD OF THE BOUNDARY AT THE BEGINNING OF THE PERIOD. AHEAD OF
THE MCS ACROSS THE LA AND TX COASTAL PLAINS...SFC HEATING AND
DEWPOINTS IN THE 65 TO 70 F RANGE SHOULD RESULT IN MODERATE
INSTABILITY BY MIDDAY. ALTHOUGH LARGE-SCALE ASCENT IS FORECAST TO BE
WEAK...INCREASING LOW-LEVEL CONVERGENCE AHEAD OF THE FRONTAL ZONE
SHOULD RESULT IN SCATTERED THUNDERSTORM INITIATION DURING THE
AFTERNOON.

FORECAST SOUNDINGS THIS AFTERNOON ACROSS THE REGION SHOW MODERATE
VERTICAL SHEAR PROFILES AND STEEP MID-LEVEL LAPSE RATES SUGGESTING
THE ENVIRONMENT WILL BE FAVORABLE FOR SUPERCELLS WITH LARGE HAIL
ESPECIALLY UPON INITIATION. HOWEVER...AS STORMS INCREASE IN COVERAGE
BY THE LATE AFTERNOON AND EARLY EVENING...THE DOMINANT STORM MODE
REMAINS QUESTIONABLE. THE WEAK LARGE-SCALE ASCENT AND LINEARLY
ORIENTED CONVERGENCE ZONE MAY HELP STORMS TO ORGANIZE QUICKLY INTO A
LINE. IF THIS OCCURS...THE STRONGER CELLS IN THE LINE SHOULD STILL
BE CAPABLE OF LARGE HAIL AND ISOLATED WIND DAMAGE. THE LINE SHOULD
CONTINUE SEWD MOVING INTO THE IMMEDIATE COASTAL AREAS BY THE EARLY
EVENING.

FURTHER SOUTH ACROSS SOUTH TX AND THE TX HILL COUNTRY...FORECAST
SOUNDINGS SHOW INCREASING VERTICAL SHEAR PROFILES DURING THE DAY AS
A MID-LEVEL JET NOSES INTO THE REGION. THIS COMBINED WITH MODERATE
INSTABILITY AND STEEP MID-LEVEL LAPSE RATES SHOULD BE FAVORABLE FOR
SUPERCELLS WITH LARGE HAIL AND ISOLATED WIND DAMAGE AS STORMS
INITIATE IN THE AFTERNOON. DUE TO THE STRONGER VERTICAL SHEAR...THE
SUPERCELL POTENTIAL THROUGH THE LATE AFTERNOON AND EVENING APPEARS
GREATER THAN AREAS FURTHER NORTH. THIS COULD SUSTAIN THE THREAT FOR
LARGE HAIL AND WIND DAMAGE THREAT LONGER INTO THE EVENING.
HOWEVER...ANY SEVERE THREAT SHOULD DIMINISH BEFORE MIDNIGHT DUE TO
THE RELATIVELY WEAK LARGE-SCALE ASCENT AND DECREASING INSTABILITY.

...TN VALLEY/SRN APPALACHIANS/CAROLINAS...
AT UPPER-LEVELS...A BROAD RIDGE OVER THE MS VALLEY WILL DRIFT EWD
AND DAMPEN OUT IN WLY FLOW. AT THE SFC...A COLD FRONT WILL MOVE SWD
ACROSS THE REGION. SOUTH OF THE BOUNDARY...SFC DEWPOINTS IN THE 60S
F SHOULD ALLOW MODERATE INSTABILITY TO DEVELOP BY AFTERNOON.
ALTHOUGH LARGE-SCALE ASCENT SHOULD REMAIN RELATIVELY
WEAK...STRENGTHING LOW-LEVEL CONVERGENCE ALONG AND AHEAD OF THE
FRONTAL BOUNDARY AND SFC HEATING SHOULD ALLOW STORMS TO INITIATE IN
TN...NRN AL AND THE SRN APPALACHIAN MTNS DURING THE AFTERNOON.

FORECAST SOUNDINGS THIS AFTERNOON ACROSS THE REGION SHOW THE
STRONGEST VERTICAL SHEAR PROFILES ACROSS TN AND THE SRN APPALACHIAN
MTNS WHERE THE SEVERE THREAT WILL LIKELY BE THE GREATEST. 0-6 KM
SHEAR VALUES OF 30 TO 40 KT SHOULD BE SUFFICIENT FOR SUPERCELLS
BEFORE A GRADUAL TRANSITION TO LINEAR DEVELOPMENT WHICH IS LIKELY IN
THE LATE AFTERNOON. THE STRONGER CELLS IN THE LINE SHOULD BE CAPABLE
OF LARGE HAIL AND ISOLATED WIND DAMAGE ESPECIALLY NEAR PEAK HEATING.
HOWEVER...THE LINE SHOULD GRADUALLY WEAKEN DURING THE EARLY EVENING
AS THE CONVECTION ENCOUNTERS WEAKER VERTICAL SHEAR OVER CNTRL AL AND
NCNTRL GA.

FURTHER EAST ACROSS THE CAROLINAS...WEAK INSTABILITY SHOULD DEVELOP
AHEAD OF A SFC LOW AND FRONTAL BOUNDARY BY AFTERNOON. THIS COMBINED
WITH MODERATE VERTICAL SHEAR SHOWN ON FORECAST SOUNDINGS SHOULD BE
SUFFICIENT FOR AT LEAST AN ISOLATED SEVERE THREAT. ALTHOUGH
SUPERCELLS WILL BE POSSIBLE...QUESTIONS REMAIN CONCERNING
INSTABILITY. IF MODERATE INSTABILITY DEVELOPS...A FEW SUPERCELLS
WITH LARGE HAIL AND WIND DAMAGE COULD DEVELOP. HOWEVER...ANY SEVERE
THREAT SHOULD GRADUALLY DECREASE BY EARLY EVENING AS INSTABILITY
WEAKENS AND THE FRONT MOVES SWD ACROSS THE REGION.

..BROYLES.. 04/25/2006