[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 132000
SWODY1
SPC AC 131959

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SAT MAY 13 2006

VALID 132000Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM NRN TX EWD ACROSS LOWER MS
VALLEY INTO GA...

...GULF STATES...
SURFACE ANALYSIS SHOWED A COLD FRONT EXTENDING FROM WRN TN SWWD INTO
CENTRAL AR AND THEN WWD THROUGH CENTRAL OK TO THE TX PANHANDLE.  AN
OUTFLOW BOUNDARY FROM EARLIER CONVECTION ACROSS AL/GA EXTENDED FROM
SWRN GA/SERN AL WNWWD ACROSS SRN TO WRN AL TO NRN MS.  MOISTURE
RETURN ACROSS THE GULF COAST STATES HAS BEEN SOMEWHAT LIMITED THUS
FAR PRIMARILY TO THE SURFACE/NEAR SURFACE LAYER.  HOWEVER...PRESENCE
OF STEEP MID LEVEL LAPSE RATES IS CONTRIBUTING TO SBCAPE VALUES
AROUND 1500 J/KG OVER SRN AL TO 2000 J/KG IN NRN MS WHERE SURFACE
DEWPOINTS WERE HIGHER.

INCREASING LARGE SCALE ASCENT SPREADING SEWD ACROSS TN VALLEY AND
GULF COAST STATES THIS AFTERNOON/EVENING WITH THE APPROACH OF SRN
MO/NRN AR SHORT WAVE TROUGH/MID LEVEL SPEED MAX EXPECTED TO AID IN
THUNDERSTORM DEVELOPMENT.  HAIL WILL BE LIKELY WITH MANY OF THE
STORMS GIVEN STRONG DEEP LAYER SHEAR AND STEEP LAPSE RATES...WHILE
INDICATION OF LOW RH VALUES/DRY AIR IN LOW LEVELS PER 1730Z ACARS
DATA AT MEM SHOULD PROMOTE POTENTIAL FOR STRONG WIND GUSTS.

ALTHOUGH ERN PARTS OF AL/CENTRAL GA ARE RATHER STABLE PER CLOUDINESS
LEFT OVER FROM EARLIER CONVECTION...SLIGHT RISK WILL BE MAINTAINED
ACROSS THIS REGION GIVEN POTENTIAL FOR UPSTREAM STORMS...ONCE THEY
DEVELOP...TO TRACK INTO THIS AREA LATER THIS EVENING.

...LOWER MS VALLEY INTO NRN TX...
NWD MOISTURE RETURN IS ONGOING FROM THE TX COAST TO CENTRAL/ERN
PARTS OF THE RED RIVER VALLEY. SURFACE TEMPERATURES RISING THROUGH
THE 80S BENEATH A PLUME OF STEEP LAPSE RATES WERE CONTRIBUTING TO
INCREASING INSTABILITY AS EXPECTED PER EARLIER OUTLOOK.  HOWEVER...
THESE STEEP LAPSE RATES WERE ALSO RESULTING IN A STRONG CAP THAT IS
EXPECTED TO PRECLUDE SURFACE BASED DEVELOPMENT ALONG THE SWD MOVING
COLD FRONT UNTIL THIS EVENING ACROSS NRN TX INTO SRN AR.

MOISTURE ADVECTION THROUGH THE FORECAST PERIOD SHOULD RESULT IN
MLCAPE VALUES UP TO 2500 ACROSS ERN TX LATE THIS AFTERNOON. 
INSTABILITY EXPECTED TO REMAIN STRONG INTO THE OVERNIGHT PERIOD AS
STRENGTHENING SSWLY LLJ AIDS IN NWD MOISTURE TRANSPORT AND
INCREASING WAA.

ONCE STORMS DEVELOP...STRONG DEEP LAYER SHEAR...PER PROXIMITY OF MID
LEVEL WIND MAX EXTENDING FROM ERN KS TO TN VALLEY...AND STRONG
INSTABILITY WILL SUPPORT SUPERCELLS WITH LARGE HAIL AND DAMAGING
WINDS. AS COLD FRONT MOVES SWD ACROSS ERN TX/LOWER MS VALLEY
TONIGHT...SEVERE THREAT EXPECTED TO PERSIST WELL AFTER DARK GIVEN
PROGGED MAGNITUDE OF ELEVATED INSTABILITY/BULK SHEAR.

...ERN PA INTO PARTS OF CENTRAL/WRN NY...
AFTERNOON WATER VAPOR IMAGERY INDICATED SEVERAL VORTICITY MAXIMA
ROTATING AROUND THE ERN PERIPHERY OF THE LARGE ERN STATES UPPER
CYCLONE.  ONE SUCH MID LEVEL IMPULSE WAS LOCATED OVER NERN PA/
CENTRAL NY AND AIDING WITH ONGOING THUNDERSTORMS ACROSS ERN PA NNWWD
INTO CENTRAL/WRN NY.  ADDITIONAL LARGE SCALE ASCENT IS EXPECTED TO
SPREAD NWD ACROSS THIS SAME REGION LATER THIS AFTERNOON/EVENING AS A
PAIR OF UPSTREAM IMPULSES LOCATED OVER SERN VA AND CENTRAL NC AT 18Z
ROTATE NWD.  WEAK LOW-LEVEL CONVERGENCE ALONG SURFACE TROUGH AND
ASCENT WITH VORTICITY MAXIMA EXPECTED TO SUPPORT ADDITIONAL
THUNDERSTORMS THIS AFTERNOON AND EARLY EVENING.  WEAK INSTABILITY
/MLCAPE 500-800 J/KG/ AND MODEST DEEP LAYER SHEAR /20-25 KT/ SHOULD
LIMIT STORM ORGANIZATION...THOUGH A FEW STORMS MAY BECOME STRONG
ENOUGH TO PRODUCE MARGINALLY SEVERE HAIL AND/OR STRONG WIND GUSTS.

..PETERS.. 05/13/2006