[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 161635
SWODY1
SPC AC 161633

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1133 AM CDT SUN APR 16 2006

VALID 161630Z - 171200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS A LARGE PART OF IL INTO
SWRN IND AND FAR NWRN KY...

...THERE IS A SLGT RISK OF SVR TSTMS FROM IA TO THE NC/VA COAST...

...IA INTO THE OH RIVER VALLEY...
STRONG UPPER SYSTEM WITH NEARLY VERTICALLY STACKED LOW CENTER NOW
OVER CENTRAL IA WILL TRACK ESEWD ACROSS CENTRAL IL...WITH TRAILING
SURFACE TROUGH ADVANCING ESEWD ACROSS THE MID MS RIVER VALLEY TODAY.
 THIS WILL SUPPORT WIDESPREAD SEVERE THUNDERSTORMS INTO ERN IA AND
MUCH OF IL THIS AFTERNOON...SPREADING INTO WRN IN/NRN KY THIS
EVENING.  BOTH DEEP LAYER SHEAR AND MID LEVEL LAPSE RATES REMAIN
QUITE IMPRESSIVE ACCORDING TO OBSERVED AND FORECAST SOUNDINGS. 12Z
NAM CONTINUES TO OVERFORECAST SURFACE DEW POINTS AHEAD OF THIS
SYSTEM.  HOWEVER...COLD TEMPERATURES ALOFT/STEEP LAPSE RATES ALONG
WITH VERY STRONG LARGE SCALE ASCENT SUGGEST LOWER 60F SURFACE DEW
POINTS WILL BE MORE THAN ADEQUATE FOR MODERATE INSTABILITY AND AN
ENHANCED SEVERE THUNDERSTORM THREAT TODAY.  DEVELOPMENT WILL LIKELY
OCCUR IN TWO DIFFERENT MODES.  ONE WILL BE UNDER COLD UPPER LOW
WHERE VERY STRONG AMBIENT VORTICITY AND STEEP LOW LEVEL LAPSE
RATES/MODERATE SFC-3 KM CAPE WILL BE FOUND.  DEVELOPMENT IS ALREADY
INCREASING IN THIS ENVIRONMENT ACROSS CENTRAL IA AND WILL SHIFT INTO
NERN MO/ERN IA AND WRN IL THROUGH THE DAY.  

ADDITIONAL DEVELOPMENT IS EXPECTED TO OCCUR ALONG SURFACE WARM FRONT
EXTENDING INTO CENTRAL IND AND AHEAD OF SURFACE TROUGH ADVANCING
INTO ERN MO DURING THE AFTERNOON.  SHEAR PARAMETERS ARE STRONGER
ACROSS THIS REGION AND LOW LEVEL SHEAR WILL REMAIN STRONG DESPITE
DEEP WLY COMPONENT.  GIVEN AMOUNT OF SHEAR...MLCAPE SHOULD EXCEED
1500 J/KG AND SUPPORT SUPERCELLS ACROSS THIS REGION...WITH EVENTUAL
EVOLUTION INTO ONE OR MORE LEWP STRUCTURES.  TORNADO THREAT WILL
REMAIN HIGHEST NEAR THE WARM FRONT/AHEAD OF LOW CENTER WHERE STRONG
PRESSURE FALLS AND BACKED SURFACE WINDS WILL ENHANCE LOW LEVEL
HELICITY...THOUGH ISOLATED TORNADOES WILL LIKELY OCCUR WITH WARM
SECTOR DEVELOPMENT INTO THE OH RIVER VALLEY.  LARGE MCS SHOULD
DEVELOP AND SPREAD ESEWD INTO THE IND AND SWRN OH/KY THROUGH THE
EVENING.  DAMAGING WINDS MAY ALSO BECOME WIDESPREAD WITH THIS MCS AS
ACTIVITY ORGANIZES ALONG LEADING OUTFLOW BOUNDARY.

...WV/ERN KY INTO SRN VA/NC...
SEVERE THREAT WILL REMAIN ALONG STALLED SURFACE FRONT EXTENDING
WNW-ESE ACROSS THIS REGION TODAY.  WITH LIMITED LARGE SCALE ASCENT
AND MODEST CAPPING ON 12Z SOUNDINGS...ACTIVITY WILL LIKELY BE
STRONGLY DRIVEN BY DIURNAL HEATING.  HOWEVER...DEEP LAYER SHEAR
REMAINS STRONG WITH EFFECTIVE BULK SHEAR EXCEEDING 40 KT.  IN
ADDITION...STEEP LAPSE RATES AND 55-60F SURFACE DEW POINTS SHOULD
SUPPORT MODEST INSTABILITY BY THE MID TO LATE AFTERNOON.  LARGE HAIL
AND DAMAGING WINDS WILL REMAIN PRIMARY SEVERE THREATS WITH FAIRLY
HIGH-BASED STORMS AS THEY SPREAD ESEWD THROUGH THE EVENING. 
HOWEVER...AN ISOLATED TORNADO COULD OCCUR GIVEN LOCATION OF SURFACE
BOUNDARY/INCREASED LOW LEVEL SHEAR AND LIKELIHOOD OF PERSISTENT
SUPERCELL STRUCTURES.

..EVANS/GUYER.. 04/16/2006