Mesoscale Discussion 0707
   NWS Storm Prediction Center Norman OK
   0435 PM CDT Mon May 20 2019

   Areas affected...eastern Oklahoma...southeast Kansas...southwest
   Missouri...and Arkansas

   Concerning...Severe potential...Watch likely 

   Valid 202135Z - 202330Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Thunderstorms are developing near and along the warm
   front. Given the strong instability and highly sheared environment,
   a tornado watch may be needed for portions of the area.

   DISCUSSION...Thunderstorms are developing within a broad warm-air
   advection regime across portions of eastern Oklahoma into central
   Arkansas. At present these thunderstorms may not be fully rooted in
   the boundary layer, but given the increasingly unstable and highly
   sheared airmass, and continued northward advancement of a warm
   front, at least transient, episodic tapping of the boundary-layer
   airmass is likely. The boundary-layer airmass, characterized by
   mixed-layer CAPE values at or above 2000 J/kg and deep-layer shear
   over 50 knots, will support at least a hail threat for any sustained
   thunderstorms. Fort Smith (KSRX) VAD indicated 0-3km storm-relative
   helicity values above 500 m2/s2, suggesting that a tornado threat
   will be possible with any thunderstorm that can sustain itself in
   the boundary layer.

   Model guidance is not bullish on evolving or maintaining severe
   thunderstorms across the region in the short term, however given the
   high quality of the airmass in the vicinity of these thunderstorms,
   a lifting warm front across the region, and confidence in additional
   strong thunderstorms moving into the area from the west later this
   evening, a tornado watch will likely be needed in the next few
   hours.

   ..Marsh/Guyer.. 05/20/2019

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...JAN...LZK...SGF...SHV...TSA...ICT...

   LAT...LON   34799458 36399569 37619528 37289351 35259166 33459132
               33269333 34799458