ACUS01 KWNS 200100
SPC AC 200058
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0658 PM CST Tue Feb 19 2019
Valid 200100Z - 201200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE LOWER MISSISSIPPI VALLEY...
A marginal risk for severe storms will evolve later tonight from
Louisiana into south central Mississippi with primary risks being a
couple of strong to damaging wind gusts and perhaps a brief tornado.
...Louisiana through south central Mississippi...
A warm front situated along the LA coast will advance farther inland
this evening, reaching southern MS later tonight. The deeper forcing
for ascent resulting from a shortwave trough moving northeastward
into the southern and central Plains will remain well northwest of
the warm sector with only weak surface low development expected on
the warm front. By 12Z Wednesday this low will be situated over
southwest MS with a cold front trailing south into southwest LA. The
warm front will extend southeast from the low through southern MS.
As the moist, warm sector moves inland, dewpoints will rise to near
70 F along the LA coast and mid-upper 60s farther north into
southern MS. Persistent low-mid level ascent and destabilization
along the warm conveyor belt should promote an increase in
thunderstorms along and east of the cold front later tonight. 00Z
RAOB data show a mid-level inversion over southern LA into southern
MS. Persistent low-mid level ascent may contribute to some cooling
in the inversion layer, especially well inland from the coast,
possibly supporting more robust updrafts. However, offsetting this
will be greater likelihood of only partial erosion of the low-level
stable layer with northward extent, suggesting most storms could
remain slightly elevated. Nevertheless...storms developing in this
regime may become close to surface based, where effective storm
relative helicity and deep shear will be sufficient for some
supercell and bowing segments. Given the potential limiting factors
due primarily to weak low-level lapse rates and presence of at least
a persistent, modest mid-level inversion, will maintain marginal
risk this update.