[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 211257
SWODY1
SPC AC 211255

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0755 AM CDT FRI APR 21 2006

VALID 211300Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS TODAY INTO EARLY TONIGHT ACROSS
THE LOWER MS AND TN VALLEYS....

...LOWER MS AND TN VALLEYS...
A SRN STREAM SHORTWAVE TROUGH OVER N TX WILL CONTINUE EWD TODAY
ACROSS THE GULF COAST STATES...AROUND THE SRN PERIPHERY OF A CLOSED
LOW OVER THE UPPER MS VALLEY.  IN ADVANCE OF THE SRN STREAM
TROUGH...SMALLER SCALE CONVECTIVELY INDUCED VORTICITY MAXIMA ARE
ASSOCIATED WITH CONVECTIVE CLUSTERS OVER NRN MS AND THE UPPER TX
COAST. THE STABILIZING EFFECTS OF THESE STORM CLUSTERS WILL TEND TO
LIMIT THE SEVERE THREAT TODAY TO THE NW OF THE COMPOSITE OUTFLOW
BOUNDARY FROM SE TX ACROSS NRN LA TO NRN MS...WITH THE STRONGER
STORMS FOCUSED IN ADVANCE OF THE MCV/S AND ALONG THE REMNANT OUTFLOW
BOUNDARIES DURING THE DAY.  SURFACE OBSERVATIONS AND MORNING
SOUNDINGS SHOW BOUNDARY LAYER DEWPOINTS OF 65-70 F ACROSS LA/MS/AL
TO THE S AND E OF THE OUTFLOW BOUNDARIES.  DAYTIME HEATING WILL
COMBINE WITH THIS LOW-LEVEL MOISTURE AND MID LEVEL LAPSE RATES NEAR
7 C/KM TO SUPPORT MLCAPE VALUES OF 1500-2000 J/KG WITHIN THE WARM
SECTOR.  

VERTICAL SHEAR IN THE WARM SECTOR WILL BE MODULATED INITIALLY BY THE
WAVE MOVING NEWD FROM MS TO TN...AS CONFIRMED BY VWP TIME SERIES
ACROSS MS.  EXPECT THE STRONGER L0W-LEVEL SHEAR AND WAA TO SHIFT
NEWD FROM NRN AL TOWARD TN AND N GA THROUGH THE MORNING IN ADVANCE
OF THE NRN MS WAVE...THOUGH WEAKENING INSTABILITY WITH NWD EXTENT
AND THE EFFECTS OF ONGOING CONVECTION WILL TEND TO LIMIT THE SEVERE
THREAT TO THE N OF TN. FARTHER SW...THE BACKING FLOW WITH HEIGHT
OVER MS WILL TEND TO RECOVER TO A SOMEWHAT MORE FAVORABLE PROFILE
DURING THE DAY...AS THE NRN MS WAVE MOVES AWAY TO THE NE AND THE
PRIMARY TROUGH APPROACHES FROM THE W.  MODEST VERTICAL SHEAR BENEATH
55 KT SWLY MID LEVEL FLOW WILL SUPPORT BOWING LINE SEGMENTS AND
PERHAPS SUPERCELLS AS CONVECTION DEVELOPS ALONG THE SURFACE BOUNDARY
FROM CENTRAL LA INTO WRN MS.  CONVECTION MAY ALSO EVOLVE FROM THE
ONGOING STORMS MOVING ACROSS SE TX.  LARGE HAIL AND DAMAGING WINDS
SHOULD BE THE PRIMARY SEVERE THREATS.

..THOMPSON/JEWELL.. 04/21/2006