[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 290530
SWODY2
SPC AC 290528

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1128 PM CST TUE NOV 28 2006

VALID 301200Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE S-CNTRL OH VALLEY SWD
INTO THE LOWER MS VALLEY AND CNTRL GULF COAST...

...SYNOPSIS...

INTENSIFICATION OF SRN STREAM TROUGH IS FORECAST DURING THE DAY TWO
PERIOD AS IT TRANSLATES EWD THROUGH THE SRN PLAINS...PRIOR TO
BECOMING NEGATIVELY TILTED AND EJECTING MORE NEWD INTO THE MID MS
AND LOWER OH VALLEYS BY FRIDAY MORNING.  AN ACCOMPANYING BELT OF
STRONG /80-100 KT AT 500 MB/ MID-LEVEL FLOW WILL PROPAGATE THROUGH
THE TROUGH BASE...SPREADING THROUGH THE ARKLATEX...MID SOUTH AND
LOWER MS VALLEY REGIONS.

IN THE LOW-LEVELS...COLD FRONT INITIALLY EXTENDING FROM CNTRL LOWER
MI SWWD INTO SERN TX WILL RAPIDLY PUSH SEWD/EWD WITH SECONDARY
CYCLOGENESIS FORECAST OVER THE LOWER MS VALLEY THURSDAY. 
DIFFERENCES EXIST IN LATEST SHORT RANGE MODEL GUIDANCE WITH REGARD
TO THE TRACK AND STRENGTH OF THIS FEATURE...BUT IN GENERAL IT IS
FORECAST TO DEVELOP NEWD ALONG COLD FRONT INTO THE UPPER OH VALLEY
BY FRIDAY MORNING.

...S-CNTRL OH VALLEY SWD INTO THE LOWER MS VALLEY AND CNTRL GULF
COAST...

LARGE-SCALE PATTERN CONTINUES TO INDICATE THE POTENTIAL FOR A LOW
INSTABILITY - HIGH SHEAR SERIAL-TYPE WIND EVENT ACROSS THE REGION
THURSDAY INTO THURSDAY NIGHT.

29/00Z OBSERVED SOUNDINGS...CURRENT SURFACE OBSERVATIONS AND GOES
SOUNDER PW LOOP ALL INDICATE A FAIRLY RAPID RETURN OF LOW-LEVEL
MOISTURE THROUGH THE SABINE AND LOWER MS RIVER VALLEYS NWD INTO THE
MID SOUTH AND WRN TN VALLEY WITH 60F DEWPOINTS TO LIT AND THE MS
DELTA. SWLY LLJ WILL BE MAINTAINED AHEAD OF EVOLVING UPPER
SYSTEM...TRANSPORTING AN INCREASINGLY MOIST BOUNDARY LAYER NWD WITH
60F DEWPOINTS INTO KY...AND MID/UPPER 60S INTO THE LOWER MS VALLEY
BY THURSDAY AFTERNOON. LATEST MODEL GUIDANCE CONTINUES TO INDICATE
ONLY MARGINAL INSTABILITY /MUCAPES OF 200-600 J PER KG/ AHEAD OF
SURFACE FRONT THURSDAY...LARGELY DUE TO WEAK LOW TO MID-LEVEL LAPSE
RATES. 

DESPITE THE MARGINAL INSTABILITY...INCREASED LARGE-SCALE
FORCING...SLAB ASCENT ALONG COLD FRONT AND STRONG VERTICAL SHEAR ALL
SHOULD CONTRIBUTE TO THE INTENSIFICATION OF A LOW-TOPPED CONVECTIVE
LINE BY AFTERNOON FROM THE CONFLUENCE OF THE MS/OH RIVERS SWWD INTO
ERN AR AND CNTRL LA.  PRIMARY CONVECTIVE MODE IS EXPECTED TO BE
LINEAR WITH EMBEDDED LEWP/BOW STRUCTURES.  THE STRENGTH OF THE
AMBIENT WIND FIELDS WILL SUPPORT STORM MOTIONS OF 45-50+KT WITH THE
POTENTIAL FOR CORRIDORS OF WIND DAMAGE.

LOW-TOPPED SUPERCELLS WILL ALSO BE POSSIBLE...BOTH EMBEDDED IN LINE
OR FORMING IN MORE DISCRETE FASHION AHEAD OF PRIMARY CONVECTIVE
SYSTEM.  GIVEN THE LOW LCL HEIGHTS AND STRONG LOW-LEVEL SHEAR...THE
THREAT FOR ISOLATED TORNADOES WILL EXIST.  THIS IS ESPECIALLY THE
CASE INVOF DEEPENING SURFACE CYCLONE WHERE LOW LEVEL SHEAR/FORCING
WILL BE LOCALLY MORE INTENSE.

THIS CONVECTIVE LINE WILL RAPIDLY SHIFT EWD THROUGH THE SRN OH AND
TN VALLEYS...AS WELL AS THE CNTRL GULF COAST THURSDAY NIGHT WITH A
CONTINUING THREAT OF DAMAGING WINDS AND PERHAPS A FEW TORNADOES.

..MEAD.. 11/29/2006