[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 270553
SWODY1
SPC AC 270551

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1251 AM CDT SUN AUG 27 2006

VALID 271200Z - 281200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE CNTRL AND
SRN HIGH PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS FROM SRN PARTS OF THE UPPER OH
VALLEY INTO THE MID ATLANTIC AND NERN U.S....

...SYNOPSIS...

UPPER PATTERN WILL REMAIN PROGRESSIVE THIS PERIOD. UPPER LOW OVER CO
WILL CONTINUE EWD INTO THE CNTRL AND SRN PLAINS. FARTHER EAST...A
VORT MAX NOW OVER IND WILL MOVE EWD INTO PA AND THE NERN U.S. DURING
THE AFTERNOON. AT THE SURFACE A COLD FRONT WILL ACCOMPANY THE VORT
MAX INTO THE MID ATLANTIC AND NERN U.S. DURING THE AFTERNOON.
TRAILING PORTION OF THIS BOUNDARY WILL EXTEND SWWD INTO THE LOWER MS
VALLEY AND SRN PLAINS. A WARM FRONT CURRENTLY FROM NRN VA INTO SWRN
PA MAY LIFT SLOWLY NWD DURING THE DAY.


...CNTRL AND SRN HIGH PLAINS...

WEAK ENELY BOUNDARY LAYER FLOW IN POST FRONTAL ENVIRONMENT SHOULD
MAINTAIN LOW LEVEL DEWPOINTS IN THE UPPER 50S TO NEAR 60 INTO THE
CNTRL AND SRN HIGH PLAINS. MID LEVEL DRY SLOT WILL ADVECT NEWD
THROUGH ERN CO IN WAKE OF VORT MAX NOW OVER ERN CO. SECONDARY VORT
MAX WILL ROTATE THROUGH THE BASE OF THE EWD ADVANCING UPPER LOW AND
INTO PARTS OF THE CNTRL HIGH PLAINS DURING THE DAY. SURFACE HEATING
WITHIN DRY SLOT AND COOLING MID LEVEL TEMPERATURES ACCOMPANYING THE
UPPER LOW WILL RESULT IN STEEP LAPSE RATES DURING THE AFTERNOON. THE
STEEP LAPSE RATES AND IN SITU LOW LEVEL MOISTURE WILL RESULT IN
MODERATE INSTABILITY WITH MLCAPE AROUND 1500 J/KG. STORMS ARE
EXPECTED TO DEVELOP WITHIN ZONE OF LARGE SCALE ASCENT ACCOMPANYING
THE SHORTWAVE TROUGH AS THE BOUNDARY LAYER DESTABILIZES DURING THE
AFTERNOON. LOW LEVEL WIND FIELDS WILL REMAIN RATHER WEAK.
HOWEVER...A 40 KT MID LEVEL JET ROTATING THROUGH BASE OF UPPER
TROUGH WILL CONTRIBUTE TO FAVORABLE DEEP SHEAR FOR SUPERCELL
STRUCTURES. LARGE HAIL AND DAMAGING WIND WILL BE THE MAIN THREATS.


...SRN PORTIONS OF THE UPPER OH VALLEY THROUGH PORTIONS OF THE MID
ATLANTIC AND NERN STATES...

CORRIDOR OF LOW LEVEL DEWPOINTS IN THE UPPER 60S TO NEAR 70 SHOULD
PERSIST IN VICINITY OF WARM FRONT AS IT RETREATS SLOWLY NWD. THIS
BOUNDARY SHOULD EXTEND FROM NJ WNWWD THROUGH PA SUNDAY AFTERNOON.
PRIMARY CONCERN AND POTENTIAL OVERALL LIMITING FACTOR WILL BE DEGREE
OF DESTABILIZATION. THUNDERSTORMS WILL LIKELY CONTINUE DEVELOPING
INTO EARLY SUNDAY WITHIN ZONE OF ASCENT ACCOMPANYING A VORT MAX
CURRENTLY OVER NRN IND. THIS FEATURE SHOULD APPROACH WRN PA BY
SUNRISE. OTHER STORMS MAY CONTINUE INTO PARTS OF PA WITHIN ZONE OF
WARM ADVECTION N OF THE WARM FRONT. CLOUDS SHOULD REMAIN MORE
WIDESPREAD N OF THE FRONT FROM PARTS OF OH AND PA NWD INTO THE NERN
STATES. BEST POTENTIAL FOR DESTABILIZATION WILL EXIST NEAR AND S OF
THIS BOUNDARY. HOWEVER...WEAK MID LEVEL LAPSE RATES SHOULD LIMIT
MLCAPE TO AOB 1000 J/KG. STORMS MAY INTENSIFY ALONG AND N OF WARM
FRONT AS WARM SECTOR SOURCE REGION DESTABILIZES. SRN BRANCH OF LOW
LEVEL JET IS FORECAST TO STRENGTHEN FROM THE MID ATLANTIC INTO THE
NERN STATES IN ASSOCIATION WITH APPROACHING SHORTWAVE TROUGH. THIS
WILL RESULT IN LOW LEVEL HODOGRAPHS FAVORABLE FOR A THREAT OF
SUPERCELLS WITH LOW LEVEL MESOCYCLONES AND ISOLATED TORNADOES NEAR
WARM FRONT. OTHERWISE...THREAT OF ISOLATED DAMAGING WIND WILL EXIST
AS STORMS DEVELOP EWD ALONG AND AHEAD OF COLD FRONT.

...NERN TX AND SERN OK THROUGH PORTIONS OF THE LOWER AND MIDDLE MS
VALLEY...

STORMS ARE EXPECTED TO REDEVELOP DURING THE AFTERNOON ALONG FRONT OR
RESIDUAL CONVECTIVE OUTFLOW BOUNDARIES. THE ATMOSPHERE WILL LIKELY
ONCE AGAIN BECOME MODERATELY UNSTABLE IN VICINITY OF THESE
BOUNDARIES WHERE SURFACE HEATING CAN DEVELOP OUTSIDE OF CONVECTIVE
DEBRIS. MODEST VERTICAL SHEAR WILL SUPPORT MAINLY MULTICELLS WITH A
THREAT OF ISOLATED DAMAGING WIND. 

MCV CURRENTLY MOVING ENEWD THROUGH CNTRL OK MAY RESULT IN A GREATER
CONCENTRATION OF STORMS OVER PARTS OF AR OR SRN MO DURING THE DAY.
AN UPGRADE TO SLIGHT RISK MIGHT BE NEEDED FOR PARTS OF THIS AREA IN
LATER OUTLOOKS IF IT BECOMES MORE CERTAIN THAT ONGOING STORMS WILL
NOT EXHAUST THE INSTABILITY IN THIS REGION.

..DIAL/TAYLOR.. 08/27/2006