SPC AC 160728

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0228 AM CDT Tue May 16 2017

   Valid 181200Z - 191200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST KS
   INTO THE SOUTHERN PLAINS...

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

   ...SUMMARY...
   Severe thunderstorms are expected across parts of southeast Kansas
   into the southern Plains Thursday afternoon into the overnight
   hours. All severe hazards will be possible, including very large
   hail, damaging winds and a few tornadoes.

   ...Synopsis...
   The western upper low will shift east/southeast toward the
   southern/central Rockies on Thursday. Strong deep-layer
   southwesterly flow will persist across the southern and central
   Plains ahead of the low and forcing for ascent will increase after
   18z. At the surface, a lee cyclone will deepen in the vicinity of
   eastern NM or the TX Panhandle. A dryline will retreat westward
   during the morning, extending southward from the eastern TX
   Panhandle into western TX by late afternoon, and rich low-level
   moisture is expected ahead of this feature. Further north, a cold
   front will be draped across KS to the Great Lakes vicinity. Severe
   thunderstorms are expected to develop in the vicinity of these
   surface boundaries by late afternoon.

   ...Central/Southern Plains...

   There is some uncertainty in the location and evolution of surface
   features, with the operational NAM appearing to be a bit of an
   outlier.  It is important to note this however, because it brings
   the cold front surging southeast across the Plains much faster than
   the GFS/ECMWF. This in turn would impact the northern and western
   extent of severe probs. Have largely discounted the NAM solution for
   now, given the outlier status compared to other guidance, but model
   trends will need to be monitored closely in the coming day or two.

   Otherwise, expect isolated to scattered thunderstorms to develop
   along the sharp dryline by late afternoon as strong heating of a
   moisture-rich boundary layer leads to strong instability. Impressive
   midlevel lapse rates near 8-8.5 deg C/km and supercell-favoring
   kinematic profiles will lead to a large, potentially significant,
   hail threat. Additionally, strong winds and a few tornadoes will be
   possible. The wind threat may increase during the overnight hours as
   the cold front surges southeast and upscale growth becomes more
   likely with eastward extent.

   ..Leitman.. 05/16/2017

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