000
ACUS01 KWNS 221932
SWODY1
SPC AC 221930
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0130 PM CST WED FEB 22 2012
VALID 222000Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS
PARTS OF THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS REGION...
...20Z OUTLOOK UPDATE...TN VALLEY INTO SRN APPALACHIANS...
ENOUGH UNCERTAINTIES EXIST TO PRECLUDE MAKING SUBSTANTIVE CHANGES TO
THE 1630Z OUTLOOK. HOWEVER...GUIDANCE GENERALLY SEEMS TO INDICATE
THE SOUTHERN TENNESSEE/ALABAMA/GEORGIA BORDER AREA AS THE MOST
LIKELY FOCUS FOR SIGNIFICANT CONVECTIVE DEVELOPMENT THROUGH 22-00Z.
THIS APPEARS TO BE WHERE LOW-LEVEL WARM ADVECTION IS STRONGEST...AS
ANOTHER AREA OF AT LEAST WEAK MID-LEVEL FORCING FOR UPWARD VERTICAL
MOTION APPROACHES. A GRADUAL DESTABILIZATION OF THE BOUNDARY LAYER
IS ONGOING ACROSS THIS REGION...WITH INSOLATION AND SURFACE DEW
POINTS RISING THROUGH THE LOWER 50S. CAPE WILL REMAIN WEAK...BUT
SIZABLE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS AND STRONG MEAN
LOWER/MID TROPOSPHERIC FLOW OF 40-50+ KT SUPPORTS AT LEAST THE RISK
FOR POTENTIAL DAMAGING CONVECTIVELY ENHANCED GUSTS.
..KERR.. 02/22/2012
.PREV DISCUSSION... /ISSUED 1026 AM CST WED FEB 22 2012/
...SYNOPSIS...
A BROAD CYCLONIC MIDLEVEL FLOW REGIME WILL BE MAINTAINED ACROSS MUCH
OF THE CONUS THROUGH THE D1 PERIOD. SEVERAL LOW-AMPLITUDE
PERTURBATIONS WILL PROGRESS THROUGH THIS PATTERN...ONE OF NOTE WILL
TRANSLATE FROM THE CNTRL PLAINS INTO THE TN VALLEY BY THIS EVENING.
IN THE LOW LEVELS...A DIFFUSE WARM FRONT ANALYZED FROM SERN OK
ACROSS NRN PARTS OF MS/AL/GA/SC INTO CNTRL NC MAY LIFT SLIGHTLY
NWD...SERVING AS THE FOCUS FOR STRONG-SEVERE TSTM DEVELOPMENT THIS
AFTERNOON AND EVENING. FARTHER S...A SECONDARY WARM FRONT
--DELINEATING A MODIFIED CP AIR MASS FROM THAT OF MT ORIGIN-- WILL
LIFT NWD FROM THE SHELF WATERS ONTO THE GULF COAST. THIS BOUNDARY
MAY ALSO GIVE RISE TO ISOLATED STRONG TO POTENTIALLY SEVERE TSTM
DEVELOPMENT THIS AFTERNOON AND EVENING.
...TN VALLEY/SRN APPALACHIANS...
CLUSTERS OF ELEVATED TSTMS ARE ONGOING ACROSS TN...FORCED BY DCVA
ATTENDANT TO A WEAK LEAD IMPULSE AND WAA/ISENTROPIC ASCENT OCCURRING
TO THE N OF SURFACE WARM FRONT AT THE TERMINUS OF A 40-50 KT WSWLY
LLJ. ALONG AND S OF THE CURRENT TSTM ACTIVITY...FILTERED SUNSHINE
COUPLED WITH BOUNDARY LAYER DEWPOINTS RISING THROUGH THE 50S WILL
ALIGN WITH STEADILY COOLING MIDLEVEL TEMPERATURES TO YIELD AFTERNOON
MLCAPE VALUES OF 500-1500 J/KG.
IN THE WAKE OF THE INITIAL TSTM ACTIVITY...THE WEAKLY FORCED NATURE
OF THE LARGE-SCALE PATTERN IS MANIFEST IN NOTABLE VARIANCE IN MODEL
FORECASTS OF WHEN/WHERE SURFACE-BASED TSTMS WILL DEVELOP LATER
TODAY. CURRENT INDICATIONS ARE THAT DIURNALLY ENHANCED TSTM
DEVELOPMENT WILL BECOME INCREASINGLY LIKELY BY MID-LATE AFTERNOON
INVOF WARM FRONT AS FORCING FOR ASCENT ATTENDANT TO ABOVE-MENTIONED
UPSTREAM IMPULSE INTERACTS WITH THE DESTABILIZING BOUNDARY LAYER.
HERE...FORECAST SOUNDINGS SHOW LONG HODOGRAPHS WITH EFFECTIVE BULK
SHEAR OF 50-60 KT AND EFFECTIVE SRH OF 150-250 M2/S2. AS
SUCH...SETUP WILL BE SUPPORTIVE OF SUPERCELLS AND BOWING STRUCTURES
CAPABLE OF A FEW TORNADOES...DAMAGING WINDS AND HAIL.
EXPECT THE SEVERE WEATHER THREAT TO DIMINISH BY LATE EVENING INTO
TONIGHT OVER THE SRN APPALACHIANS AS THE BOUNDARY LAYER BEGINS TO
COOL AND STABILIZE.
...CNTRL/NERN GULF COAST...
AS MENTIONED ABOVE...SRN WARM FRONT WILL LIFT NWD THROUGH THE PERIOD
WITH BOUNDARY CURRENTLY EXTENDING FROM SRN LA ESEWD TO VICINITY OF
DEVELOPING TSTMS OVER THE SHELF WATERS OF THE NERN GULF OF MEXICO.
LARGE-SCALE FORCING FOR ASCENT IS FORECAST TO REMAIN NEGLIGIBLE AND
THE DEVELOPING TSTMS MAY SLOW THE NWD RETREAT OF THE WARM FRONT.
NONETHELESS...MODEL GUIDANCE DOES INDICATE AN INCREASING RISK FOR
ISOLATED SEVERE TSTMS LATER TODAY INTO THIS EVENING AS A
MOISTENING/DESTABILIZING BOUNDARY LAYER ALIGNS WITH A KINEMATIC
ENVIRONMENT SIMILAR TO THAT MENTIONED IN THE PREVIOUS SECTION. DUE
TO UNCERTAINTIES IN STORM COVERAGE...LOW SEVERE PROBABILITIES WILL
BE MAINTAINED. HOWEVER...AN UPGRADE TO A CATEGORICAL SLIGHT RISK
REMAINS POSSIBLE LATER TODAY.
