SPC AC 161623

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1123 AM CDT Tue May 16 2017

   Valid 161630Z - 171200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
   WESTERN OKLAHOMA AND THE EASTERN TEXAS PANHANDLE...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM WEST TEXAS
   INTO PARTS OF NEBRASKA AND IOWA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE
   PLAINS STATES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE
   PLAINS STATES...

   ...SUMMARY...
   Multiple clusters of severe thunderstorms are expected this
   afternoon and tonight within a swath from west Texas across the
   central Plains to the western Corn Belt and mid Missouri Valley. 
   Tornadoes, severe gusts, and large, damaging hail are expected
   within this corridor.  The greatest threat of a strong tornado or
   two appears to be focused over parts of western Oklahoma and the
   eastern Texas Panhandle.

   ...KS/NEB/IA/MO...
   Morning water vapor loop shows a deep trough over the western
   states, with a leading shortwave impulse rotating across NM.  12z
   model solutions remain consistent that a cluster of intense
   thunderstorms will develop by mid afternoon over parts of southwest
   KS as this shortwave trough approaches.  Strong heating is occurring
   in this region, with afternoon MLCAPE values over 3000 J/kg and
   minimal cap.  Initial storms will likely be capable of very large
   hail and isolated tornadoes, but it seems likely that rapid upscale
   growth into a fast-moving squall line will occur.  This will enhance
   the risk of damaging winds as storms spread northeastward across
   central/eastern KS and into parts of NE/IA/MO.  If storm-scale
   trends dictate, this area may be considered for an upgrade to MDT
   risk in later updates.

   ...Western OK/TX Panhandle...
   Low level moisture continues to stream rapidly northward into the TX
   Panhandle and western OK, with dewpoints now in the mid 60s across
   the region.  Model forecast soundings by mid-late afternoon suggest
   strong instability will be present with MLCAPE values over 3500 J/kg
   and 8 C/km lapse rates.  Isolated and discrete convection is
   expected to form along the dryline in the TX Panhandle and track
   northeastward through the mid-evening.  A pocket of strong low-level
   shear is forecast to develop in this region, resulting in favorable
   hodograph structures for supercells capable of very large hail and
   strong tornadoes.  Therefore have upgraded this area to MDT risk.

   ...West TX...
   Later this evening, thunderstorms will likely develop southward
   along the dryline/cold front across parts of west TX.  Large hail
   and damaging winds are expected with these storms.  However, this
   activity is not expected to develop until well after dark when the
   capping inversion will be strengthening.  This may tend to somewhat
   limit the coverage of severe storms.  The line of storms will spread
   eastward and into west-central TX overnight.

   ...MN/WI/Upper MI...
   A shortwave trough over the eastern Dakotas will track eastward and
   help to maintain scattered thunderstorms over parts of the western
   Great Lakes region.  Breaks in the clouds will help to destabilize
   this area, and may lead to a few strong/severe storms later this
   afternoon and evening.  Forecast soundings suggest sufficient
   vertical shear and CAPE to pose a risk of hail and damaging winds in
   the strongest cells.  An isolated tornado is also possible.

   ..Hart/Dean.. 05/16/2017

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