[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 131300
SWODY1
SPC AC 131258

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0658 AM CST MON MAR 13 2006

VALID 131300Z - 141200Z

...THERE IS A MDT RISK OF SVR TSTMS THIS AFTN ACROSS MUCH OF THE
OHIO VALLEY AND LWR GREAT LAKES REGION...FOR THE POSSIBILITY OF A
CONTINUING SEVERE WEATHER OUTBREAK...INCLUDING THE POTENTIAL FOR
DAMAGING WINDS AND ISOLATED STRONG TORNADOES....

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
AREA...EAST OF THE MISSISSIPPI VALLEY THROUGH THE NRN AND CENTRAL
APPALACHIANS AND NRN MID ATLANTIC COAST STATES....

A BROAD COLD UPPER TROUGH CONTINUES TO LIFT OUT OF THE WESTERN
STATES.  THE POLAR TROUGH IS PROGGED TO REMAIN IN PHASE WITH THE
SUBTROPICAL STREAM...AND PROGRESS INTO THE EASTERN HALF OF THE
NATION BY EARLY TUESDAY.  THE MOST SIGNIFICANT EMBEDDED SHORT WAVE
TROUGH/JET STREAK HAS LIFTED OUT OF THE BASE OF THIS FEATURE... INTO
THE UPPER MISSISSIPPI VALLEY...WITH ASSOCIATED DEEP SURFACE CYCLONE
NOW APPROACHING THE UPPER GREAT LAKES REGION.

ANOTHER UPSTREAM IMPULSE ALREADY APPEARS TO LIFTING ACROSS THE SOUTH
CENTRAL HIGH PLAINS.  AS THIS FEATURE CONTINUES NORTHEASTWARD...IT
IS EXPECTED TO CONTRIBUTE TO FURTHER DEEPENING OF THE LOW/MID-LEVEL
CYCLONE ACROSS THE UPPER GREAT LAKES REGION INTO EASTERN
ONTARIO/WESTERN QUEBEC LATER TODAY/TONIGHT.

WHILE FAVORABLE LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION SEEMS
LIKELY TO SUPPORT THE CONTINUATION OF A SEVERE WEATHER OUTBREAK INTO
THE NORTHEASTERN QUARTER OF THE NATION ...UNCERTAINTIES ARE ARISING
WHICH COULD POSSIBLY LIMIT THE MAGNITUDE OF CONVECTIVE POTENTIAL.  A
RETURN FLOW OF 60F+ DEW POINTS IS OCCURRING OFF THE GULF OF
MEXICO...AHEAD OF COLD FRONT INTO THE WESTERN SLOPES OF THE
APPALACHIANS...WITH ANOTHER RETURN FLOW DEVELOPING OFF THE WESTERN
ATLANTIC INTO THE MID ATLANTIC COAST STATES.  HOWEVER...COLD CORE OF
UPPER TROUGH WILL CONTINUE TO LAG WARM SECTOR THROUGH THIS FORECAST
PERIOD...AND NORTHEASTWARD ADVECTION OF ELEVATED MIXED LAYER FROM
THE PLATEAU REGION IS BEING SUPPRESSED.  FURTHER COMPLICATING
MATTERS...CLOUD COVER FROM WIDESPREAD OVERNIGHT CONVECTION MAY
RESTRICT INSOLATION.

ALL OF THIS IS EXPECTED TO LIMIT PEAK MIXED LAYER CAPE TO AROUND
1000 J/KG IN A CORRIDOR AHEAD OF SURFACE COLD FRONT ADVANCING TOWARD
THE APPALACHIANS THIS AFTERNOON...AND PERHAPS JUST SOUTH OF WARM
FRONT ACROSS PARTS OF THE NORTHERN MID ATLANTIC COAST STATES. 
THOUGH CONVECTIVE INSTABILITY MAY NOT BE PARTICULARLY STRONG...
STRENGTHENING FLOW/SHEAR IN CONDITIONALLY UNSTABLE WARM
SECTOR...JUST EAST OF 100+ KT 500 MB JET STREAK SHIFTING INTO THE
LOWER GREAT LAKES REGION...WILL SUPPORT DAMAGING WIND/TORNADO THREAT
IN THUNDERSTORM ACTIVITY.

...GREAT LAKES/OHIO VALLEY...
THE PRIMARY SEVERE THREAT SEEMS LIKELY TO EXIST WITH ONGOING
PRE-FRONTAL CONVECTIVE LINE NOW ADVANCING INTO THE LOWER OHIO
VALLEY.  THIS ACTIVITY SHOULD CONTINUE EASTWARD IN THE VICINITY OF A
50+ KT SOUTHERLY LOW-LEVEL JET...WHICH WILL PROVIDE LARGE LOW-LEVEL
HODOGRAPHS SUPPORTING CONTINUING RISK FOR TORNADIC SUPERCELLS. 
ISOLATED STRONG TORNADOES ARE POSSIBLE...PARTICULARLY DURING THE
PEAK AFTERNOON HEATING...ACROSS PARTS OF EASTERN KENTUCKY/OHIO INTO
WESTERN PENNSYLVANIA.

BEST CHANCE FOR REDEVELOPMENT UPSTREAM IS EXPECTED IN CLOSER
PROXIMITY TO THE SURFACE CYCLONE...ACROSS LOWER MICHIGAN...WHERE
ENVIRONMENT IS ALSO EXPECTED TO BE SUFFICIENT FOR ISOLATED
SUPERCELLS WITH POTENTIAL FOR TORNADOES.

AS COLD FRONT SURGES THROUGH THE LOWER GREAT LAKES LATER THIS
EVENING/TONIGHT...FORCING COULD SUPPORT SOLIDIFYING CONVECTIVE LINE
WITH POTENTIAL FOR DAMAGING WINDS...EASTWARD ACROSS PARTS OF CENTRAL
NEW YORK/PENNSYLVANIA.

...NORTHERN MID ATLANTIC STATES...
RELATIVELY STEEP LAPSE RATES MAY DEVELOP BY AFTERNOON WITH STRONG
HEATING IN THE LEE OF THE NORTH CENTRAL APPALACHIANS...WHERE SHEAR
PROFILES WILL ALREADY BE SUFFICIENT FOR SUPERCELLS...WELL AHEAD OF
MAIN UPPER SYSTEM.  AIDED BY BROAD WARM ADVECTION AND MOISTURE
RETURN FROM THE ATLANTIC...STORMS MAY DEVELOP DURING THE AFTERNOON
HOURS...WITH POTENTIAL FOR LARGE HAIL/DAMAGING WINDS AND ISOLATED
TORNADOES.

...LOWER MISSISSIPPI VALLEY/GULF STATES...
LOW-LEVEL MOISTURE/INSTABILITY WILL BE SOMEWHAT GREATER THAN AREAS
FARTHER TO THE NORTH.  THIS COULD CONTRIBUTE TO STRONG/SEVERE
CONVECTIVE DEVELOPMENT...INCLUDING ISOLATED SUPERCELLS...IN NARROW
PRE-FRONTAL CORRIDOR.  HOWEVER...OVERALL POTENTIAL SEEMS LIMITED AS
LOW-LEVEL SUBTROPICAL RIDGING IS SLOW TO WEAKEN WITH MAIN UPPER
FORCING SHIFTING TO NORTH OF REGION.

..KERR/GRAMS.. 03/13/2006