Storm Prediction Center increases sections of Louisiana, Arkansas and Mississippi to Moderate Risk

From the SPC:

…THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM FAR EAST TEXAS ACROSS NORTHERN LOUISIANA AND SOUTHERN ARKANSAS INTO WEST-CENTRAL MISSISSIPPI…

…SUMMARY…
Numerous severe thunderstorms are expected across portions of east Texas, Louisiana, southern Arkansas, Mississippi and surrounding areas Saturday and Saturday night.

…Synopsis…
As an upper low/trough shifts northeastward across the Great Lakes into eastern Canada, an evolving trough pivoting around the western and southern fringe of this system will shift out of the southern Rockies and across southern Plains Saturday/Saturday night.

In response to this system, a surface low — initially expected to reside in the vicinity of the Texas Hill Country — will strengthen as it shifts northeastward. By the end of the period Sunday morning, the low should reside in the vicinity of the confluence of the Ohio and Mississippi Rivers. Trailing from this low, a cold front will sweep across east Texas to near the Sabine River by sunset, and then continue eastward across the lower Mississippi River into Mississippi and eventually western Alabama. Widespread thunderstorms — including potential for a substantial severe weather event — are expected.

…east Texas eastward to southwest Tennessee/Mississippi/western Alabama…
A potentially significant severe weather episode is expected to evolve across portions of the south central U.S. — focused from the Arklatex to the lower Mississippi Valley area, as a seasonably strong southern-stream storm system advances across the region.

With a moist low-level airmass within an evolving warm sector undergoing ample daytime heating, mixed-layer CAPE in the 1000 to 2000 J/kg range is expected to evolve by early to mid afternoon. Increasing ascent associated with the eastward advance of the upper system should result in an increase in convection by early afternoon. CAM guidance varies from model to model, but general consensus appears reasonable — in that a band of storms will develop near the front, with some linear/upscale growth with time, while more cellular convection evolves ahead of the band. At this time, the banded convection appears likely to evolve across east Texas, with the more cellular storms affecting northern Louisiana and southern Arkansas by mid afternoon, and then spreading across the Mississippi Delta region into western Mississippi by mid to late afternoon. Given very strong the very strong wind field accompanying this system, with flow veering/increasing with height from southeasterly to south-southwesterly, and reaching 60 to 70 kt at mid levels, well-organized rotating updrafts will likely evolve within several cells. Along with locally damaging winds and hail, strong tornadoes may also occur, within a few of the most intense storms. Convection will continue spreading eastward through the evening and into the overnight hours. While the pre-frontal, cellular convection should diminish overnight, a semi-organized band of storms — with embedded rotating updrafts and continued severe/tornado potential — will cross the central Gulf Coast states through the end of the period.

…MAXIMUM RISK BY HAZARD…
Tornado: 15% SIG – Moderate
Wind: 45% – Enhanced
Hail: 30% – Enhanced

For Mississippi: