[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 011712
SWODY2
SPC AC 011711

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1111 AM CST SAT APR 01 2006

VALID 021200Z - 031200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF IA...MO AND MUCH
OF IL...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE GREAT LAKES SWD INTO
THE MID SOUTH AND ARKLATEX...

--POTENTIALLY SIGNIFICANT SEVERE WEATHER EPISODE IS BEING FORECAST
ACROSS THE MIDWEST AND MID MS VALLEY SUNDAY AND SUNDAY NIGHT--

...SYNOPSIS...

MID AND UPPER-LEVEL TROUGH NOW OVER THE PACIFIC NW AND GREAT BASIN
WILL TRANSLATE EWD INTO THE GREAT PLAINS LATE SATURDAY NIGHT INTO
SUNDAY MORNING...PRIOR TO INTENSIFYING INTO A CLOSED CIRCULATION
OVER THE UPPER MIDWEST SUNDAY NIGHT.  AS THIS OCCURS...ACCOMPANYING
MID AND HIGH-LEVEL JET STREAKS WILL PROPAGATE THROUGH THE TROUGH
BASE INTO MO AND IL/IND SUNDAY AFTERNOON AND EVENING.

IN THE LOW-LEVELS...PRIMARY SURFACE LOW INITIALLY OVER ERN NEB WILL
DEVELOP ENEWD INTO LOWER MI BY MONDAY MORNING. ASSOCIATED WARM
FRONT WILL CONCURRENTLY LIFT NEWD THROUGH THE OH VALLEY AND GREAT
LAKES WHILE TRAILING COLD FRONT SURGES EWD THROUGH THE MID/LOWER MO
AND MS VALLEYS AND INTO THE OH AND TN VALLEYS THROUGH THE FORECAST
PERIOD.

...MID/LOWER MO VALLEY INTO THE GREAT LAKES...MID MS AND OH
VALLEYS...

A NW-SE ORIENTED BAND OF MAINLY ELEVATED TSTMS IS EXPECTED TO BE
ONGOING 02/12Z FROM VICINITY OF THE SURFACE LOW OVER ERN NEB/WRN IA
INTO WRN KY AND MIDDLE TN...LARGELY DRIVEN BY WAA ALONG BROAD SWLY
LLJ.  THIS ACTIVITY WILL LIKELY CONTINUE THROUGH THE PERIOD AHEAD OF
RETREATING WARM FRONT INTO THE GREAT LAKES WITH THE STRONGEST STORMS
CAPABLE OF MAINLY LARGE HAIL.

IN THE WAKE OF THIS INITIAL ACTIVITY...THE PRESENCE OF STEEP
MID-LEVEL LAPSE RATES / 7-8 C/KM / COUPLED WITH BOUNDARY-LAYER
DEWPOINTS IN THE LOW TO MID 60S WILL CONTRIBUTE TO A MODERATELY
UNSTABLE AIR MASS ACROSS SYSTEM WARM SECTOR WITH MLCAPES INCREASING
TO 1500-2500 J/KG FROM SERN SE/CNTRL MO SWWD INTO THE ARKLATEX AND
LOWER MS VALLEY.

INCREASED FORCING FOR ASCENT AHEAD OF MID-LEVEL TROUGH AND EXIT
REGIONS OF ACCOMPANYING JET STREAKS WILL CONTRIBUTE TO RAPID
SURFACE-BASED TSTM DEVELOPMENT BY EARLY TO MID AFTERNOON FROM NEAR
SURFACE LOW OVER WRN OR CNTRL IA SWD ALONG COLD FRONT INTO MO. 
ADDITIONAL SURFACE-BASED STORMS WILL ALSO BE POSSIBLE AT THIS TIME
ALONG WARM FRONT.

FORECAST SOUNDINGS INDICATE A POTENT COMBINATION OF INSTABILITY AND
VERTICAL SHEAR ACROSS MODERATE RISK AREA...WHICH SHOULD SUPPORT
INTENSE SUPERCELL DEVELOPMENT WITH THE POTENTIAL FOR A FEW STRONG
TORNADOES IN ADDITION TO VERY LARGE...DESTRUCTIVE HAIL AND DAMAGING
WINDS. WITH TIME...STORMS MAY EVOLVE INTO BOWING LINE SEGMENTS OR A
MESOSCALE LEWP STRUCTURE WITH CORRIDORS OF DAMAGING WINDS POSSIBLE
EWD ACROSS THE OH VALLEY SUNDAY NIGHT.

...MID SOUTH INTO ARKLATEX...

AS MENTIONED ABOVE...PRE-FRONTAL AIR MASS IS FORECAST TO BECOME
MODERATELY UNSTABLE BY AFTERNOON OWING TO STEEPENING LAPSE RATES AND
A MOIST BOUNDARY-LAYER.  GIVEN A STRONGER CAP AND THAT LARGE-SCALE
FORCING FOR ASCENT AND LOW-LEVEL FRONTAL CONVERGENCE WILL TEND TO
WEAKEN WITH SWD EXTENT...SOME UNCERTAINTY EXISTS WITH REGARD TO
EVENTUAL CONVECTIVE COVERAGE AND INTENSITY ACROSS REGION.  LATEST
SHORT TERM MODEL GUIDANCE SUGGESTS THAT TSTMS SHOULD BEGIN TO BUILD
SWWD ALONG FRONT BY MID TO LATE AFTERNOON FROM NEAR THE CONFLUENCE
OF THE OH AND MS RIVERS INTO PORTIONS OF ERN AR...WRN TN AND PERHAPS
SWD INTO NRN LA AND NRN MS.

THE COMBINATION OF MODERATE INSTABILITY AND 45-55 KT WLY MID-LEVEL
FLOW SUGGEST THE THREAT FOR A FEW SUPERCELLS AND BOWING LINE
SEGMENTS CAPABLE OF DAMAGING WINDS...LARGE HAIL AND A FEW TORNADOES.
 THIS SEVERE THREAT WILL LIKELY CONTINUE SUNDAY NIGHT ACROSS THE TN
VALLEY AND NRN PORTIONS OF MS AND AL.

..MEAD.. 04/01/2006