SPC AC 140547

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1247 AM CDT Sun May 14 2017

   Valid 151200Z - 161200Z

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

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
   WESTERN KS INTO THE TX SOUTH PLAINS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE UPPER MIDWEST...

   ...SUMMARY...
   Isolated severe thunderstorms are expected across parts of western
   Kansas into the Texas Panhandle vicinity. Strong winds and large
   hail will be the main threat with these storms. Additional strong
   storms are possible mainly overnight across parts of eastern South
   Dakota, southern and central Minnesota and perhaps far northern Iowa
   and west-central Wisconsin. Hail will be the main threat with these
   storms.

   ...Synopsis...
   The Pacific coast upper trough will pivot eastward on Monday to the
   Great Basin and southwestern deserts. A broad area of enhanced
   southwesterly deep-layer flow will stretch from the southern Rockies
   through the Plains and into the Upper Midwest. In response to the
   eastward progression of the trough, the upper ridge extending from
   the upper MS Valley to the Ozarks will shift east of the MS River.
   Weak shortwave impulses will migrate through broader southwesterly
   flow and, in combination with more substantial height falls after
   00z, aid in thunderstorm development across parts of the Upper
   Midwest during the nighttime hours. Further south, a surface trough
   will extend southward through the central and southern High Plains
   and a dryline will be the focus for thunderstorm activity across
   parts of western KS into the TX Panhandle vicinity during the late
   afternoon/early evening. 

   ...Western KS into the TX Panhandle Vicinity...

   A surface trough will sharpen during the afternoon and southeasterly
   low level flow will advect moisture northwest across the southern
   Plains ahead of a dryline. With the lack of any stronger shortwave
   impulse ejecting across the southern Rockies, thunderstorm activity
   will be diurnally driven and isolated. However, deep-layer shear
   profiles will be sufficient for high-based supercells. Steep
   midlevel lapse rates approaching 8.0 deg C/km and moderate
   instability will support storms capable of large hail. A deeply
   mixed boundary layer to around 700 mb, where flow is progged to be
   around 40 kt, also will support strong wind potential. As storms
   track east toward the eastern TX Panhandle and adjacent portions of
   western KS, loss of daytime heating and increasing capping is
   expected to result in rapid weakening of storms near dark.

   ...Eastern SD, southern/central MN, far northern IA, west-central
   WI...

   Strong capping should inhibit convection across the warm sector
   during the afternoon. A weak surface low will develop over the
   northern High Plains and track eastward across SD overnight. A warm
   from will extend eastward from the low, with some variability among
   deterministic guidance in how far north the front will advance
   during the nighttime hours. However, the front should be lifting
   northward in the vicinity of eastern SD to southern/central MN and
   west-central WI overnight. A south/southwesterly low-level jet will
   increase after 00z from the central Plains into the upper MS Valley.
   Strong warm advection atop the surface boundary, coupled with
   falling midlevel heights, should support elevated thunderstorm
   development north of the front. Steeper-than-normal midlevel lapse
   rates for this time of year and sufficient deep-layer shear will
   support a hail threat with these storms. Given uncertainty in the
   location of the surface boundary and lack of stronger forcing aloft,
   will introduce only low severe probs at this time.

   ..Leitman.. 05/14/2017

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