DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 271612
SWODY1
SPC AC 271610

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1110 AM CDT SAT APR 27 2013

VALID 271630Z - 281200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT FROM
SW TX TO PARTS OF TN/MS/AL...

...AR/TN/MS...
MORNING SATELLITE IMAGERY SHOWS A COMPACT UPPER LOW OVER WESTERN
MO...AND A SHORTWAVE TROUGH EXTENDING SOUTHWARD FROM THE LOW INTO
WESTERN AR. THE TROUGH WILL ROTATE EASTWARD TODAY INTO THE MID MS
VALLEY AND PROVIDE LARGE SCALE ASCENT FOR THE DEVELOPMENT OF
SCATTERED SHOWERS AND THUNDERSTORMS. SURFACE ANALYSIS INDICATES A
LOW OVER SOUTHEAST OK AND A WARM FRONT EXTENDING EASTWARD ACROSS
CENTRAL AR INTO SOUTHWEST TN. INCREASING BREAKS IN THE CLOUDS TO
THE SOUTH OF THE WARM FRONT WILL HELP TO SLOWLY DESTABILIZE THE AIR
MASS...WHILE DEWPOINTS CLIMB INTO THE MID 60S. THIS SCENARIO SHOULD
RESULT IN A FOCUSED AREA OF STRONG/SEVERE THUNDERSTORM DEVELOPMENT
LATER THIS AFTERNOON AND EVENING ACROSS PARTS OF EASTERN AR/WEST
TN/NORTHERN MS. FORECAST SOUNDINGS SHOW STRONG EFFECTIVE SHEAR AND
0-3KM HELICITY VALUES OF 150-250 M2/S2. THESE PARAMETERS COUPLED
WITH SUFFICIENT INSTABILITY WILL PROMOTE THE RISK OF SUPERCELLS
CAPABLE OF LARGE HAIL...DAMAGING WINDS...AND ISOLATED TORNADOES.
ACTIVITY WILL SPREAD EASTWARD THROUGH THE EVENING INTO MIDDLE TN AND
NORTHWEST AL BEFORE WEAKENING.

...LA/EAST TX...
A COLD FRONT CURRENTLY EXTENDS FROM THE AFOREMENTIONED LOW OVER
SOUTHEAST OK INTO EAST TX. THIS BOUNDARY IS EXPECTED TO SAG
SOUTHEASTWARD INTO NORTHWEST LA BY LATE AFTERNOON. MODEL SOLUTIONS
ARE IN AGREEMENT THAT THE CAPPING INVERSION SHOULD WEAKEN THROUGH
THE DAY LEADING TO SCATTERED THUNDERSTORMS ALONG THE FRONT. LOW
LEVEL SHEAR IS EXPECTED TO BE RATHER WEAK...BUT SUFFICIENT DEEP
LAYER FLOW AND MODERATE INSTABILITY WILL PROMOTE STRONG UPDRAFTS
CAPABLE OF HAIL AND GUSTY WINDS.

...SOUTH CENTRAL TX...
THE COLD FRONT IS FORECAST TO EXTEND FROM AUS WESTWARD ACROSS THE
HILL COUNTRY LATER THIS AFTERNOON. MORNING STRATUS TO THE SOUTH OF
THE FRONT IS SLOWLY BURNING OFF...WHICH SHOULD HELP TO YIELD
AFTERNOON MLCAPE VALUES OF 2500 J/KG. DEEP WEAK EASTERLY LOW LEVEL
FLOW BENEATH MODERATELY STRONG WESTERLY FLOW AT MID LEVELS WILL
PROVIDE SUFFICIENT SHEAR FOR ORGANIZED/SUPERCELL STORMS CAPABLE OF
LARGE HAIL AND DAMAGING WINDS.

..HART/PETERS.. 04/27/2013

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