[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 210532
SWODY2
SPC AC 210531

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1231 AM CDT WED JUN 21 2006

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM MUCH OF THE LWR GREAT
LAKES/OHIO VALLEY REGION INTO THE SOUTH CENTRAL HIGH PLAINS....

WHILE THE SOUTHERN BRANCH OF HIGHER LATITUDE SPLIT FLOW PATTERN
REMAINS GENERALLY ZONAL NEAR OR JUST SOUTH OF THE CANADIAN U.S.
BORDER THROUGH THIS FORECAST PERIOD...MODELS CONTINUE TO INDICATE
THAT SIGNIFICANT AMPLIFICATION WILL OCCUR IN THE NORTHERN STREAM
...ACROSS EASTERN CANADA.  THIS SHOULD BE WELL UNDERWAY BY 12Z
THURSDAY...WHEN A STRONG SHORT WAVE TROUGH IS FORECAST TO BE IN THE
PROCESS OF DIGGING THROUGH SOUTHERN HUDSON BAY/NORTHERN ONTARIO.

IN ADVANCE OF THE NORTHERN BRANCH SYSTEM...WHICH IS PROGGED TO TURN
EASTWARD ACROSS ONTARIO INTO WESTERN QUEBEC THURSDAY/THURSDAY
NIGHT....A SIGNIFICANT SOUTHERN BRANCH IMPULSE WILL CONTINUE LIFTING
ACROSS QUEBEC THROUGH THE CANADIAN MARITIMES.  AS THIS
OCCURS...STRONGER SOUTHERLY LOW-LEVEL FLOW FIELDS WILL LIFT OUT OF
THE NORTHEAST...BUT WESTERLY LOWER/MID TROPOSPHERIC FLOW WILL
INTENSIFY AHEAD OF SIGNIFICANT SURFACE COLD FRONT ADVANCING THROUGH
SOUTHEASTERN CANADA.  THIS WILL GENERALLY OCCUR ACROSS THE LOWER
GREAT LAKES INTO NORTHERN NEW ENGLAND...BUT THE SOUTHERN FRINGE OF
MORE MODERATE WESTERLIES COULD EXTEND AS FAR SOUTH/WEST AS NORTHERN
PARTS OF THE LOWER OHIO VALLEY THROUGH MUCH OF THE PERIOD.

ACROSS THE WEST...ANOTHER MID-LEVEL JET STREAK/IMPULSE PROGRESSING
ACROSS THE NORTHERN INTERMOUNTAIN REGION/ROCKIES APPEARS LIKELY TO
BE INCONSEQUENTIAL TO SIGNIFICANT CONVECTIVE DEVELOPMENT DURING THIS
PERIOD.  BUT...AN IMPULSE IN THE WEAKER SUBTROPICAL STREAM TO THE
SOUTH/EAST COULD ENHANCE CONVECTIVE POTENTIAL TO THE LEE OF THE
SOUTH CENTRAL ROCKIES.

...MIDDLE MISSISSIPPI VALLEY EASTWARD THROUGH THE NORTHEAST...
CONSIDERABLE UNCERTAINTIES EXIST.  HOWEVER...IT APPEARS MOST
PROBABLE THAT SUBSTANTIAL CONVECTIVE CLUSTER ASSOCIATED WITH INITIAL
SOUTHERN BRANCH IMPULSE WILL WEAKEN AS IT PROGRESSES ACROSS THE
HUDSON/CHAMPLAIN VALLEY THROUGH NORTHERN NEW ENGLAND EARLY THURSDAY.
 LOW-LEVEL MOISTURE IN ADVANCE OF SYSTEM ACROSS THIS REGION DOES NOT
APPEAR LIKELY TO MAINTAIN VIGOROUS CONVECTION. 
BUT...MOISTENING/DAYTIME HEATING ACROSS THE NORTH CENTRAL
APPALACHIANS...AND THE URBAN CORRIDOR FROM WASHINGTON D.C./BALTIMORE
THROUGH NEW YORK CITY...COULD BE SUFFICIENT TO SUPPORT NEW STRONG
STORMS ON THE LEADING EDGE OF CONVECTIVELY GENERATED COLD
POOL...POSSIBLY BY EARLY AFTERNOON.

IN THE WAKE OF WEAKENING CONVECTIVE SYSTEM...DOUBTS ARE INCREASING
CONCERNING LIKELIHOOD OF SIGNIFICANT DESTABILIZATION FROM PARTS OF
NORTHERN NEW YORK INTO NEW ENGLAND...AHEAD OF STRONG COLD FRONT
WHICH COULD ADVANCE INTO THE LOWER GREAT LAKES/ST. LAWRENCE VALLEY
AS EARLY AS LATE THURSDAY AFTERNOON.  IT NOW APPEARS MOST LIKELY
THAT COMPOSITE OUTFLOW BOUNDARY/PRE-FRONTAL CONFLUENT ZONE WILL BE
THE FOCUS FOR PRIMARY CONVECTIVE DEVELOPMENT.  THIS FEATURE IS
EXPECTED TO STALL NEAR OR JUST SOUTH OF THE NEW YORK/PENNSYLVANIA
BORDER...SOUTHWESTWARD THROUGH THE MIDDLE MISSISSIPPI VALLEY...
BEFORE SLOWLY ADVANCING SOUTHWARD AS CONVECTION INCREASES LATE
THURSDAY/THURSDAY NIGHT.  ACTIVITY...PARTICULARLY ACROSS THE OHIO
VALLEY/SOUTHERN GREAT LAKES...COULD BE ENHANCED BY A SHEARING
SUBTROPICAL STREAM IMPULSE...GRADUALLY ACCELERATING OUT OF THE
CENTRAL PLAINS.

SEVERAL CLUSTERS OF STORMS APPEAR POSSIBLE...IN THERMODYNAMIC
ENVIRONMENT WITH RELATIVELY STEEP LAPSE RATES AND MIXED LAYER CAPE
IN EXCESS OF 2000 J/KG.  MOMENTUM ON SOUTHERN FRINGE OF WESTERLIES
IS EXPECTED TO SUPPORT STORM MOTIONS OF 30-35+ KT...WHICH SHOULD
CONTRIBUTE TO DAMAGING WIND POTENTIAL...IN ADDITION TO LARGE HAIL.

...SOUTH CENTRAL PLAINS...
MOIST UPSLOPE FLOW IN WAKE OF COMPOSITE OUTFLOW BOUNDARY ADVANCING
SOUTHWARD TO THE LEE OF THE CENTRAL ROCKIES WILL CONTRIBUTE TO LARGE
SCALE ASCENT/DESTABILIZATION IN STEEP LAPSE RATE ENVIRONMENT.  THIS
IS EXPECTED TO SUPPORT CONVECTIVE DEVELOPMENT OFF THE HIGHER TERRAIN
LATE THURSDAY AFTERNOON.  FLOW WILL BE RATHER WEAK...BUT VEERING
WINDS WITH HEIGHT BENEATH NORTHWESTERLY MID-LEVEL FLOW MAY PROVIDE
SUFFICIENT DEEP LAYER SHEAR FOR MID-LEVEL UPDRAFT ROTATION IN
STRONGER STORMS.  AIDED BY WEAK UPPER IMPULSE...ACTIVITY COULD
CONSOLIDATE INTO ANOTHER MESOSCALE CONVECTIVE SYSTEM WITH ISOLATED
DAMAGING WIND GUSTS...IN ADDITION TO HAIL...AS IT PROGRESSES
INTO/THROUGH THE TEXAS PANHANDLE REGION THURSDAY NIGHT.

..KERR.. 06/21/2006