SPC MD 399

MD 0399 CONCERNING SEVERE POTENTIAL...TORNADO WATCH LIKELY FOR EASTERN TEXAS THROUGH EXTREME WESTERN LOUISIANA

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

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

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

LAT...LON   31489588 31999457 31709347 31169310 30469325 30339473
            30209578 31489588 

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