Severe Storm Outlook Narrative (AC)
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ACUS01 KWNS 180545
SWODY1
SPC AC 180544

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1144 PM CST Tue Jan 17 2017

Valid 181200Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF SOUTHWESTERN LOUISIANA AND SOUTHEASTERN TEXAS...

...SUMMARY...
Isolated damaging wind gusts cannot be ruled out with thunderstorms
tonight across portions of southwestern Louisiana and southeastern
Texas.

...Synopsis...
An area of midlevel cyclonic flow, and a jet streak along its
eastern flank, are forecast to track eastward across portions of the
south-central States. As this occurs, a weak wave is forecast to
develop northeastward along a surface front draped from south Texas
to the lower MS Valley region.

...Portions of southwestern Louisiana and southeastern Texas...
Despite the very modest low-level mass response to the approaching
jet streak, onshore flow ahead of the wave will maintain a moist
boundary layer across portions of the western/central Gulf Coast
vicinity. Tuesday evening soundings at Lake Charles and Corpus
Christi indicate mean mixing ratios around 13-15 g/kg, and similar
moisture will support marginal buoyancy on the warm side of the
front through the period.

Areas of showers and thunderstorms will likely be continuing into
the day across portions of eastern TX and western LA, in response to
initial warm advection. Thereafter, a renewed potential for
thunderstorm activity will likely accompany low-level ascent related
to the progressive frontal wave tonight, after additional inland
moistening occurs. Sufficient deep shear will exist around the jet
streak to support weakly organized convective clusters, perhaps
supporting localized damaging wind gusts.

However, the presence of weak low-level flow and poor midlevel lapse
rates will marginalize the severe risk. The Marginal area has been
confined to areas of anticipated greatest inland moistening amid the
enhanced vertical shear, though areal reductions or removal of the
Marginal area may become necessary in subsequent outlooks.

..Cohen/Dean.. 01/18/2017

$$



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