SPC AC 271623

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1123 AM CDT THU JUN 27 2013

   VALID 271630Z - 281200Z

   ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING
   ACROSS PARTS OF CENTRAL AND EASTERN KANSAS...

   ...THERE IS A SLGT RISK OF SVR TSTMS TODAY INTO TONIGHT ACROSS PARTS
   OF THE CENTRAL PLAINS INTO THE OZARK PLATEAU...

   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING
   ACROSS PARTS OF THE UPPER MIDWEST AND GREAT LAKES...

   ...THERE IS A SLGT RISK OF SVR TSTMS TODAY ALONG THE EASTERN SLOPES
   OF THE APPALACHIANS INTO THE ATLANTIC COASTAL PLAIN...

   ...SYNOPSIS...
   FURTHER AMPLIFICATION OF THE UPPER FLOW PATTERN ACROSS THE EASTERN
   PACIFIC INTO THE WESTERN U.S. IS FORECAST THROUGH THIS PERIOD. 
   UPPER RIDGING EXTENDING NORTH OF A BROAD SUBTROPICAL HIGH CENTERED
   NEAR THE FOUR CORNERS REGION IS EXPECTED TO SHARPEN NORTHWARD ACROSS
   THE NORTHERN U.S. ROCKIES INTO ALBERTA.  AS THIS OCCURS...THE FIRST
   COUPLE IN A SERIES OF MID/UPPER SPEED MAXIMUM...WITHIN A STRONG JET
   NOSING INLAND OFF THE PACIFIC AROUND THE CREST OF THE UPPER
   RIDGE...SHOULD CONTINUE TO DIG ACROSS THE NORTHERN PLAINS TOWARD THE
   OHIO VALLEY.

   AN UPPER TROUGH...WITH AN EMBEDDED LOW/MID-LEVEL CYCLONE... ALREADY
   APPROACHING THE NORTHERN/CENTRAL APPALACHIANS...SHOULD PROGRESS
   EASTWARD TOWARD NORTHERN MID ATLANTIC COASTAL AREAS LATER
   TODAY...THEN NORTHEASTWARD TOWARD NEW ENGLAND TONIGHT...AS BROADER
   SCALE UPPER TROUGHING BEGINS TO AMPLIFY ACROSS THE GREAT LAKES AND
   OHIO VALLEY.  MEANWHILE...A CONVECTIVELY GENERATED OR ENHANCED
   PERTURBATION TRAILING THE LEAD IMPULSE APPEARS LIKELY TO MIGRATE
   SOUTH SOUTHEASTWARD INTO/THROUGH EASTERN GULF COASTAL AREAS.

   ASSOCIATED WITH THIS EVOLVING PATTERN...STEEPEST MID-LEVEL LAPSE
   RATES...ASSOCIATED WITH VERY WARM AND STRONGLY CAPPING ELEVATED
   MIXED LAYER AIR...WILL REMAIN CONFINED TO THE CENTRAL AND SOUTHERN
   PLAINS...AND PROBABLY ERODED FROM NORTH TO SOUTH ACROSS THE CENTRAL
   PLAINS...PERHAPS FROM THE SOUTH AND EAST ACROSS TEXAS. 
   HOWEVER...MID-LEVEL LAPSE RATES REMAIN MODESTLY STEEP ACROSS PARTS
   OF THE UPPER MIDWEST...MUCH OF THE MISSISSIPPI VALLEY...AND THE
   CENTRAL/EASTERN GULF STATES...NORTHEASTWARD TO THE LEE OF THE
   CENTRAL AND SOUTHERN APPALACHIANS...WITH SOME STEEPENING POSSIBLE
   WITH WEAK MID-LEVEL COOLING ACROSS THE LOWER GREAT LAKES TOWARD THE
   HUDSON/CHAMPLAIN VALLEY TODAY.  WITH SEASONABLY MOIST CONDITIONS
   PREVAILING ACROSS MUCH OF THE MID MISSOURI VALLEY AND ADJACENT
   CENTRAL PLAINS...AND MOST AREAS EAST OF THE MISSISSIPPI VALLEY...
   DESTABILIZATION WITH DAYTIME HEATING SHOULD CONTRIBUTE TO
   CONSIDERABLE THUNDERSTORM ACTIVITY TODAY...INCLUDING THE RISK FOR
   SEVERE STORMS.  OTHER SCATTERED THUNDERSTORM ACTIVITY APPEARS
   POSSIBLE BENEATH THE WESTERN RIDGE...MAINLY ACROSS THE HIGHER
   TERRAIN FROM THE SOUTHERN SIERRA NEVADA INTO THE CENTRAL ROCKIES.

   ...CENTRAL PLAINS INTO OZARK PLATEAU...
   ISOLATED SEVERE STORM DEVELOPMENT IS ALREADY UNDERWAY ACROSS PARTS
   OF THE MID MISSOURI VALLEY.  THIS APPEARS IN RESPONSE TO FORCING
   ASSOCIATED WITH A ZONE OF ENHANCED LOWER/MID TROPOSPHERIC WARM
   ADVECTION ON THE NORTHEASTERN PERIPHERY OF THE SUBTROPICAL
   HIGH...AND THE STRONGER CAPPING ELEVATED MIXED LAYER AIR ACROSS THE
   CENTRAL AND SOUTHERN PLAINS.  THIS IS EXPECTED TO PERSIST THROUGH
   THE DAY...WITH UPSCALE CONVECTIVE GROWTH POSSIBLE INTO ONE OR TWO
   SUBSTANTIVE SOUTHWARD PROPAGATING CONVECTIVE CLUSTERS...BENEATH
   MODERATELY STRONG NORTHWESTERLY MID/UPPER FLOW.  DEEP LAYER SHEAR
   WILL BE MORE THAN SUFFICIENT FOR ORGANIZED STORM
   DEVELOPMENT...INCLUDING SUPERCELLS.  GIVEN THE THERMODYNAMIC
   PROFILES...CHARACTERIZED BY STEEP MID-LEVEL LAPSE RATES...LARGE
   CAPE...AND SIZABLE SUB-CLOUD TEMPERATURE-DEW POINT
   SPREADS...STRONGEST STORMS WILL BE CAPABLE OF PRODUCING VERY LARGE
   HAIL...PERHAPS WIND DRIVEN...ALONG WITH STRONG SURFACE COLD POOLS
   CAPABLE OF PRODUCING SWATHS OF DAMAGING WIND GUSTS.

   ...ERN GULF STATES AND APPALACHIANS TO ATLANTIC SEABOARD...
   DEEP LAYER SHEAR ACROSS MUCH OF THE REGION IS EXPECTED TO REMAIN
   WEAK THROUGH THE PERIOD.  HOWEVER...FORCING ASSOCIATED WITH THE MAIN
   IMPULSE TURNING EAST OF THE NORTH CENTRAL APPALACHIANS...COUPLED
   WITH AN ASSOCIATED BELT OF MODEST LOWER/MID-LEVEL FLOW...COULD
   ENHANCE CONVECTIVE DEVELOPMENT LATE THIS AFTERNOON ACROSS PARTS OF
   EASTERN VIRGINIA/MARYLAND AND THE DELMARVA PENINSULA INTO NORTHERN
   MID ATLANTIC COASTAL AREAS.  A LINE OR CLUSTER OF STORMS APPEARS
   POSSIBLE...WITH THE RISK FOR POTENTIALLY DAMAGING WIND GUSTS.  

   OTHER SCATTERED STRONG/SEVERE STORM DEVELOPMENT STILL APPEARS
   POSSIBLE IN THE PRESENCE OF MODERATE INSTABILITY...NORTHWARD INTO
   UPSTATE NEW YORK...AND SOUTHWARD...TO THE SOUTH AND EAST OF THE
   SOUTHERN APPALACHIANS.  IT IS POSSIBLE THAT THE CONVECTIVELY
   ENHANCED PERTURBATION COULD CONTRIBUTE TO ANOTHER CLUSTER OVER
   STORMS TODAY ACROSS PARTS OF ALABAMA AND GEORGIA...WHICH COULD
   PERHAPS DEVELOP SOUTHWARD INTO NORTHERN FLORIDA.

   ...UPPER MIDWEST INTO GREAT LAKES...
   WEAK TO MODERATE INSTABILITY AND STRENGTHENING DEEP LAYER SHEAR
   ...TO THE CYCLONIC SIDE OF THE MID/UPPER JET STREAK NOSING SOUTHWARD
   THROUGH THE UPPER MISSISSIPPI VALLEY...MAY CONTRIBUTE TO SCATTERED
   STRONG/SEVERE STORM DEVELOPMENT TODAY INTO TONIGHT.  THIS MAY
   INCLUDE A COUPLE OF SUPERCELLS.

   ..KERR/GRAMS.. 06/27/2013

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