SPC AC 160558

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1258 AM CDT Sun Apr 16 2017

   Valid 161200Z - 171200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN AND CENTRAL PLAINS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OUTSIDE OF THE
   SLIGHT RISK AREA FROM PARTS OF THE SOUTHERN PLAINS NORTHEASTWARD
   INTO THE MID MISSISSIPPI VALLEY...OHIO VALLEY AND CENTRAL TO
   NORTHERN APPALACHIANS...

   ...SUMMARY...
   Isolated to scattered severe thunderstorms with a potential for
   large hail and wind damage are possible today across parts of the
   southern Plains into the northern Ozarks.  Marginally severe
   thunderstorms with strong wind gusts and hail are also possible from
   the Ohio Valley into the central and northern Appalachians.

   ....Southern and Central Plains/Northern Ozarks...
   West southwest mid-level flow will be in place today across the
   southern Plains. At the surface, a cold front will move slowly
   southward across the Texas Panhandle, northern Oklahoma and western
   Missouri. A moist airmass will be in place south of the front with
   surface dewpoints in the mid 60s F. As surface heating takes place
   across the warm sector today, moderate to strong instability is
   expected to develop ahead of the front from the southern Plains into
   the northern Ozarks. This along with increasing low-level
   convergence along the boundary should result in the initiation of
   scattered thunderstorms during the mid to late afternoon from the
   southeast Texas Panhandle northeastward across western and northern
   Oklahoma into southwest Missouri. Forecast soundings along this
   corridor at 00Z/Monday show MLCAPE values in the 2000 to 3000 J/Kg
   range along with steep mid-level lapse rates. This along with 30 to
   35 kt of 0-6 km shear should be enough for rotating cells and
   organized line segments. Supercells with large hail and wind damage
   will be possible across parts of the southern Plains along the axis
   of strongest instability. Wind damage may also occur with short
   multicell line segments. The current thinking is that several small
   clusters of strong to severe thunderstorms will move southeastward
   across the slight risk area during the late afternoon and early
   evening. Isolated strong to severe thunderstorms will also be
   possible to the east of a surface trough in west Texas but limited
   large-scale ascent should help to keep any severe threat marginal
   there.

   ...Central and Northern Appalachians/Ohio Valley/Mid Mississippi
   Valley...
   Westerly mid-level flow will be in place across the Ohio Valley and
   lower Great Lakes region today. At the surface, a cold front will
   advance eastward across the region today with a narrow corridor of
   low-level moisture in place just ahead of the front. Surface
   dewpoints should range from the mid 50s F in the central Appalachian
   mountains to the lower 60s F in the Ohio Valley. As surface heating
   takes place, weak instability is forecast to develop along the
   front. This combined with increasing low-level convergence should
   result in thunderstorm development by midday from eastern Ohio
   northeastward into northwest Pennsylvania and western New York. This
   convection is forecast to organize into a line and move eastward
   across central New York and western Pennsylvania during the early to
   mid afternoon. Forecast soundings along this corridor at 21Z show
   unidirectional wind profiles above 850 mb along with strong speed
   shear in the low to mid-levels. This along with steep low-level
   lapse rates should result in an isolated wind damage threat with
   hail also possible. The threat should remain marginal due to weak
   instability.

   Further southwest across the mid Mississippi Valley and lower Ohio
   Valley, scattered thunderstorm development is forecast to occur
   along and ahead of the front this afternoon.  Although pockets of
   moderate instability may develop along this corridor, forecast
   soundings suggest 0-6 km shear will remain mostly below 30 kt. This
   should marginalize any severe threat with isolated damaging wind
   gusts and hail as the primary hazards.

   ..Broyles/Mosier.. 04/16/2017

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