Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 210038
SWOMCD
SPC MCD 210037
LAZ000-TXZ000-210230-

Mesoscale Discussion 0080
NWS Storm Prediction Center Norman OK
0637 PM CST Fri Jan 20 2017

Areas affected...southeast Texas through southwest Louisiana

Concerning...Severe potential...Watch possible

Valid 210037Z - 210230Z

Probability of Watch Issuance...60 percent

SUMMARY...Threat for mainly a few instances of damaging wind and
large hail will persist over southeast TX next couple hours,
spreading into southwest LA by mid evening. With time threat for a
few tornadoes is expected to increase, especially across southern
LA.

DISCUSSION...Early this evening a warm front separating rich Gulf
moisture from modified continental-polar air extends from southeast
LA westward to along the southeast TX coast. This boundary should
slowly develop inland, especially later tonight as the low-level jet
strengthens across LA. In the meantime, thunderstorms are expected
to continue developing initially over southeast TX, but spreading
into southwest LA by mid evening as a northeastward-ejecting
shortwave trough enhances ascent north of this boundary. As steeper
mid-level lapse rates advect eastward in the presence of low-level
theta-e advection, instability will increase and the thermodynamic
environment should become more supportive of robust updrafts. Strong
effective bulk shear will support some supercell and bowing
structures with initial threats being mainly large hail and damaging
wind. Weak low-level winds may initially limit short-term tornado
potential. However, the tornado threat is expected to increase by
mid-evening onward and especially later tonight over southern LA as
the strengthening low-level jet augments 0-1 km hodograph size.

..Dial/Edwards.. 01/21/2017

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

ATTN...WFO...LCH...HGX...

LAT...LON   29759328 29709399 29489470 30089500 30839411 31009278
            30659198 29879202 29759328



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