Mesoscale Discussion 0673
   NWS Storm Prediction Center Norman OK
   0516 PM CDT Sat May 18 2019

   Areas affected...portions of northern into southwestern LA and
   southeast TX

   Concerning...Severe potential...Watch likely 

   Valid 182216Z - 190015Z

   Probability of Watch Issuance...80 percent

   SUMMARY...A new tornado watch is likely across portions of northern
   into southwest LA and southeast TX this evening.

   DISCUSSION...Severe storms currently intensifying across portions of
   northern and central Texas WW 183 and 184 will track east/northeast
   this evening into portions of southeast TX and northern, central and
   southwest LA. Effective shear may decrease modestly later this
   evening, but will remain sufficient to maintain severe convection
   within favorable thermodynamic environment and vertically veering
   low level shear resulting in continued tornado threat. So far,
   convection in Texas has shown mixed convective mode with some bowing
   segments and some semi-discrete supercells. Expect this will
   continue across the MCD are, though some guidance suggests a
   tendency toward more linear modes. In fact, recent VWP from KPOE
   showed evidence increasing 2-3 km winds (near 50 kt). Regardless,
   mean mixing ratios greater than 16 g/kg backed low level flow will
   support low LCLs and rotation either from embedded/semi-discrete
   cells or in mesovortices along leading edge of bowing structures. 

   Additionally, isolated cells were developing in warm advection/weak
   ascent across northern and central LA. Low level shear is not
   impressive across this area currently, but strong instability and
   modest midlevel lapse rates could result in an uptick in intensity,
   especially as shear improves across the region the next few hours.

   A new tornado watch will likely be needed across the MCD area within
   the next 1-2 hours.

   ..Leitman/Guyer.. 05/18/2019

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

   ATTN...WFO...JAN...LCH...SHV...HGX...FWD...

   LAT...LON   30609368 30369533 30399596 30639619 30919598 31649526
               32249447 32709355 33029278 33109231 33069207 32839178
               32249182 31669212 31099264 30789324 30609368