[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 160611
SWODY1
SPC AC 160609

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0109 AM CDT SUN APR 16 2006

VALID 161200Z - 171200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID MS/OH VALLEYS TO
MID-ATLANTIC STATES...

...SYNOPSIS...
WELL DEFINED CLOSED UPPER LOW...NOW LOCATED OVER ERN NEB PER WATER
VAPOR IMAGERY...IS EXPECTED TO WEAKEN/BECOME AN OPEN WAVE TODAY AS
IT MOVES ESEWD THROUGH MID/UPPER RIDGE AXIS ALONG THE MS VALLEY. 
BAND OF 55-65 KT MID-LEVEL FLOW ALONG SRN PERIPHERY OF THIS TROUGH
SHOULD EXTEND FROM THE MID MS VALLEY TO VA/NC BY THIS AFTERNOON.  IN
THE LOW-LEVELS...SURFACE LOW OVER SWRN IA AT 12Z THIS MORNING WILL
TRACK SEWD ALONG WARM FRONT THROUGH CENTRAL/SRN IL THIS AFTERNOON...
AND THEN ACROSS SRN IND/NRN KY LATE THIS EVENING/OVERNIGHT. 
TRAILING COLD FRONT WILL SPREAD EWD ACROSS LOWER MO TO LOWER OH
VALLEYS...WITH THE SRN EXTENT MOVING SLOWLY SWD ACROSS THE SRN
PLAINS. 

...MID MS/OH VALLEYS...
AT 12Z TODAY...THUNDERSTORMS SHOULD BE ONGOING FROM PARTS OF THE
UPPER MS VALLEY SEWD INTO THE OH VALLEY...PRIMARILY ALONG/N OF
SURFACE WARM FRONT.  LOW-LEVEL WAA AND LARGE SCALE ASCENT AHEAD OF
UPPER TROUGH SHOULD MAINTAIN THIS EARLY ACTIVITY N OF WARM FRONT. 
SURFACE HEATING EXPECTED IN THE WARM SECTOR COMBINED WITH RESIDUAL
MOISTURE /SURFACE DEWPOINTS IN THE UPPER 50S-LOWER 60S/ ALONG THIS
BOUNDARY AND STEEP LAPSE RATES WILL SUPPORT MLCAPE VALUES UP TO
2000-2500 J/KG BY EARLY-MID AFTERNOON FROM SERN IA/ERN MO INTO THE
OH VALLEY.  THERMODYNAMICS COMBINED WITH LARGE SCALE ASCENT AHEAD OF
UPPER TROUGH WILL ALLOW NEW THUNDERSTORMS TO DEVELOP BY EARLY
AFTERNOON FROM SURFACE LOW SEWD ALONG THE WARM FRONT AND SWD ALONG
THE COLD FRONT INTO SERN MO.  STRONG DEEP LAYER SHEAR WILL SUPPORT
ORGANIZED STORMS WITH SUPERCELLS POSSIBLE ESPECIALLY WITH INITIAL
ACTIVITY FROM SERN IA/ERN MO INTO IL WHERE SHEAR VECTORS WILL BE
ORIENTED MORE NORMAL TO SURFACE BOUNDARIES.  BACKED LOW-LEVEL FLOW
VICINITY SURFACE LOW/ALONG WARM FRONT IS EXPECTED TO ENHANCE THE
THREAT FOR TORNADOES...WHILE STEEP LAPSE RATES ALSO SUPPORT A THREAT
FOR VERY LARGE HAIL WITH SOME OF THE INITIAL STORMS.  MODELS SUGGEST
UPSCALE GROWTH INTO A FORWARD-PROPAGATING MCS ACROSS IL/IND AND
WRN-NRN KY LATER THIS AFTERNOON/EVENING AS LOW-LEVEL JET VEERS AND
SHEAR VECTORS BECOME ORIENTED PARALLEL TO WARM FRONT.  DAMAGING
WINDS SHOULD BECOME THE PRIMARY THREAT WITH THE MCS AS IT TRACKS
SEWD THROUGH THE OH VALLEY...POTENTIALLY REACHING WV/WRN VA LATE IN
THE PERIOD. 

STRONGER CAP LOCATED SOUTH OF MID-LEVEL JET AXIS SHOULD LIMIT SWD
EXTENT OF SEVERE THREAT ALONG THE COLD FRONT TO THE VICINITY OF THE
SERN MO/NERN AR BORDER REGION. 

...MID-ATLANTIC STATES...
POCKETS OF SURFACE HEATING EXPECTED TO OVERCOME WEAKLY CAPPED AIR
MASS BY LATE MORNING/EARLY AFTERNOON TO AID IN THUNDERSTORM
DEVELOPMENT ALONG THE SURFACE BOUNDARY.  STEEP LAPSE RATES COMBINED
WITH SURFACE DEWPOINTS IN THE 50S TO AROUND 60 ALONG THE SURFACE
BOUNDARY EXPECTED TO SUPPORT MLCAPE VALUES AROUND 1000 J/KG BY THIS
AFTERNOON.  FAIRLY DEEP UNI-DIRECTIONAL WIND FIELDS AND STRONG DEEP
LAYER SHEAR WILL SUPPORT A THREAT FOR ORGANIZED SEVERE STORMS. 
GIVEN STORMS SHOULD BE TIED TO SURFACE HEATING... THREAT SHOULD
DECREASE AFTER SUNSET AS AIR MASS BEGINS TO STABILIZE WITH THE LOSS
OF DAYTIME HEATING.  

...NRN HIGH PLAINS...
ENTRANCE REGION OF SWLY MID-LEVEL JET THAT MOVED INLAND OVER ORE/NRN
CA SATURDAY EVENING PER 00Z UPPER AIR ANALYSIS IS EXPECTED TO BE
LOCATED OVER THE NRN HIGH PLAINS BY LATE THIS AFTERNOON/EARLY
EVENING.  LARGE SCALE ASCENT ASSOCIATED WITH THIS FEATURE WILL AID
IN THUNDERSTORM DEVELOPMENT THIS AFTERNOON AS COLD FRONT MOVES EWD
ACROSS ERN MT/WY.  INCREASING SSELY LOW-LEVEL WINDS BY LATE
AFTERNOON/EVENING OVER THE WRN DAKOTAS SHOULD AID IN THE TRANSPORT
OF A NARROW PLUME OF MOISTURE BENEATH PLUME OF STEEP LAPSE RATES. 
THUS...WEAK INSTABILITY MAY SUPPORT AN ISOLATED SEVERE THREAT WITH
STORMS THAT FORM ALONG THE COLD FRONT AS IT MOVES EWD ACROSS THE NRN
HIGH PLAINS THIS EVENING.

..PETERS/GRAMS.. 04/16/2006