Day 1 Severe Weather Outlook

Valid 021200Z – 031200Z


Strong to severe thunderstorms may impact parts of the central Gulf
coast today, accompanied by a risk for damaging wind gusts and a
tornado or two.

…Central Gulf Coast States…
A low-amplitude upper-level ridge will move northeastward today
across the Gulf Coast States as southwest mid-level flow becomes
established from the southern Plains into the lower Mississippi
Valley. At the surface, a cold front will advance southeastward
across the southern Plains as moisture advection, associated with a
50 to 60 kt low-level jet, takes place in the lower Mississippi
Valley. In response, surface dewpoints should increase in the mid to
upper 60s F across parts of the region. Although cloud cover should
minimize surface heating, weak instability should still be in place
by afternoon across southeast Louisiana and south-central
Mississippi. Thunderstorms appear likely to develop around midday
along the northwestern edge of the moist sector from central
Louisiana into central Mississippi. This convective line should
gradually organize and move eastward across the Lower Mississippi
Valley and central Gulf Coast States this afternoon.

Although mid-level flow will be anticyclonic across the Gulf Coast
States today, an 80 to 100 kt mid-level jet will cause deep-layer
shear to steadily increase. Forecast soundings this afternoon at
Baton Rouge, LA and Hattiesburg, MS increase 0-6 km shear values
into the 65 to 75 kt range. This combined with strong speed shear
and some directional shear in the lowest 1 km AGL will likely result
in a severe threat. A conditional potential for rotating storms may
develop with cells that initiate ahead of the squall line. Rotating
cells will also be possible along the stronger parts of the line.
Due to the strong low-level shear with 0-3 km storm relative
helicity near 400 m2/s2, the stronger rotating storms may obtain a
tornado threat. A couple tornadoes will be possible across southeast
Louisiana and south-central Mississippi. The more organized cells
may also produce damaging wind gusts with a few damaging wind gusts
also accompanying the stronger segments of the squall-line.

..Broyles.. 01/02/2020


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