SPC AC 280700

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CST Tue Feb 28 2017

   Valid 011200Z - 021200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   MISSISSIPPI AND ALABAMA NORTHEASTWARD INTO EASTERN KENTUCKY AND THE
   UPPER OHIO VALLEY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER
   MISSISSIPPI VALLEY NORTHEASTWARD INTO THE OHIO VALLEY AND WESTERN
   CAROLINAS AND NORTHWARD INTO THE MID-ATLANTIC STATES AND INTO NEW
   JERSEY AND PENNSYLVANIA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK...

   ...SUMMARY...
   Strong to severe thunderstorms will be possible from the lower
   Mississippi Valley northeastward across the Tennessee Valley and
   southern Appalachians, and northward into parts of the Mid-Atlantic
   states and into portions of the Northeast.  Damaging winds are
   forecast to be the predominant severe hazard.

   ...Synopsis...
   A large-scale mid-level trough axis over the central states will
   move eastward into the lower Great Lakes/Mid-Atlantic states.  A
   100+ kt 500-mb speed max will translate generally eastward from the
   OH Valley through New England and the Mid-Atlantic region during the
   period.  In the low levels, a surface low is forecast to develop
   northeastward from near Detroit to northern parts of New England
   Wednesday night as a warm front advances northward across much of
   the northeastern U.S.  A cold front initially over the OH Valley
   extending south-southwestward into the lower MS Valley will sweep
   eastward across much of the eastern U.S. by early Thursday morning. 

   ...northern parts of AL/MS northeastward into the central
   Appalachians and Mid-Atlantic states...
   A squall line will likely be ongoing Wednesday morning across the OH
   Valley with some possible breaks and lower storm coverage farther
   south into the lower MS Valley.  A risk for damaging winds will
   accompany the convective line as a plume of low-level moisture
   --featuring surface dewpoints ranging from around 60 degrees F at
   the OH River to the middle 60s in MS/AL-- contributes to 500-1000
   J/kg MUCAPE ahead of the cold front. Although some slight timing
   differences still exist in the models, favoring a timing solution
   similar to the ECMWF/CMC.  

   A strong deep-layer wind field of southwesterly flow from 50-60 kt
   at 850 mb and increasing with height to 70-100 kt in the midlevels,
   will aid in the potential risk for widespread wind damage associated
   with a squall line and other linearly organized storm clusters. 
   Some tornado risk may develop as well with mature linear bands
   (short-lived QLCS variety) or where greater destabilization occurs. 
   Uncertainty remains regarding destabilization to the east of the
   mountains in the Mid-Atlantic region.  Will defer adding higher
   severe probabilities for this area for the time being.  

   The activity will push east of the Appalachians by early evening and
   encounter gradually decreasing buoyancy in part due to the loss of
   heating and deeper inland mixing from southern GA northeastward
   along the Carolina coastal plain.  As a result, there will likely be
   a corresponding decrease in the potential for damaging winds farther
   south in parts of the Southeast.

   ...northern PA into NY and southern New England...
   Strong low-level moisture/warm-air-advection into this area will
   lead to weak destabilization ahead of the cold front.  Models vary
   on the degree of destabilization leading to uncertainty regarding
   coverage of strong/severe storms.  Very strong low- to
   mid-tropospheric flow coupled with several hundred SBCAPE may result
   in some of the stronger storms or a convective line to potentially
   be capable of a risk for primarily damaging winds.

   ..Smith.. 02/28/2017

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