Mesoscale Discussion 0399 NWS Storm Prediction Center Norman OK 0904 AM CDT Sun Apr 02 2017 Areas affected...eastern Texas through extreme western Louisiana Concerning...Severe potential...Tornado Watch likely Valid 021404Z - 021630Z Probability of Watch Issuance...95 percent SUMMARY...The threat for tornadoes is expected to increase from late morning into the afternoon over a portion of east TX. A tornado watch will likely be issued for parts of east TX into western LA by 16Z, and a PDS tornado watch is being considered. The new watch might also replace the eastern portion of tornado watch 108. DISCUSSION...Early this morning numerous discrete to semi-discrete storms including supercells are developing within a zone of warm advection and isentropic ascent in the vicinity of a warm front located from southern LA through eastern TX. The storms north of the warm front are likely slightly elevated, while activity along and just south of this boundary are probably ingesting near-surface-based inflow parcels. Current expectations are for the storms well north of the warm front to weaken as they move north into the more stable boundary layer across northeast TX, but may still pose a short term large hail threat. Visible imagery indicates some diabatic warming may commence by mid morning over southeast TX, contributing to further boundary layer destabilization near the warm front. The front should move slowly north as the low-level jet strengthens across eastern TX into far western LA in response to forcing for ascent within exit region of an upper jet rotating through base of synoptic trough. Increasing 0-1 km hodograph size resulting from the strengthening LLJ and destabilization of the boundary layer should contribute to an increasing threat for supercells with strong low-level mesocyclones and tornadoes as storms continue developing in vicinity of the warm front. ..Dial/Hart.. 04/02/2017 ATTN...WFO...LCH...SHV...HGX...FWD... LAT...LON 31489588 31999457 31709347 31169310 30469325 30339473 30209578 31489588