Mesoscale Discussion 0857
   NWS Storm Prediction Center Norman OK
   1140 AM CDT Sun May 18 2025

   Areas affected...Northeast Oklahoma into northwest Arkansas and far
   southwest Missouri

   Concerning...Severe potential...Watch possible 

   Valid 181640Z - 181845Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Elevated thunderstorms developing across northeast
   Oklahoma into northwest Arkansas and southwest Missouri may pose a
   hail threat through early afternoon. Confidence in the coverage and
   duration of this threat is uncertain, but convective trends will be
   monitored.

   DISCUSSION...Isentropic ascent over a residual convective outflow
   across northeast OK/northwest AR has promoted scattered
   thunderstorms within the past hour. Based on forecast soundings and
   surface observations, this convection is likely being driven by
   ascent within the 850-700 mb level on the eastern fringe of an EML.
   Steep lapse rates above this layer (around 8 C/km) is supporting
   MUCAPE values between 1500-2000 J/kg, and strong flow within the
   850-250 mb layer is supportive effective shear values around 50
   knots. Consequently, organized convection is possible and may pose a
   severe hail threat through the next few hours. Weak ascent along the
   outflow boundary may be insufficient for sustained deep convection
   despite the favorable convective environment, and stable conditions
   in place downstream across northern AR/southern MO should limit the
   spatial extent of the threat. As such, overall coverage, duration,
   and intensity is uncertain. However, if convection can persist
   through mid afternoon, additional heating may support a higher
   potential for sustained/intense storms. Watch issuance is currently
   not likely, but convective trends will continue to be monitored
   given the environment.

   ..Moore/Hart.. 05/18/2025

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

   ATTN...WFO...LZK...SGF...TSA...

   LAT...LON   35089407 35239499 35779567 35999572 36219568 36719447
               36709389 36459356 36179327 35929306 35639287 35389299
               35269311 35139351 35089407 

   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN