Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS02 KWNS 261731
SPC AC 261730
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1130 AM CST Sun Feb 26 2017
Valid 271200Z - 281200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE LOWER MISSISSIPPI VALLEY...
A few strong to severe storms will be possible over a portion of the
lower Mississippi Valley on Monday. Primary threats will be damaging
wind gusts and some hail.
Downstream from a positive-tilt synoptic trough amplifying over the
western states, broad west-southwesterly flow aloft will prevail. A
deamplifying shortwave trough will move from the lower-middle
Mississippi Valley at the start of the period to the Middle Atlantic
Area late Monday afternoon. At the surface a lee-low will develop
over the central High Plains, while a warm front advances north
through eastern TX and the lower MS valley. A dryline will also
evolve across central TX.
...Lower Mississippi Valley region...
An MCS should be in progress 12Z Monday from western TN through a
portion of LA. Storms along southern end of the MCS may pose an
ongoing marginal risk for small to marginally severe hail and a few
strong wind gusts. The warm sector south and east of this activity
will destabilize with the onset of diabatic warming within an
environment of 40-50 kt 0-6 km shear. However, tendency will be for
the low-level jet to gradually shift east of this region in
association with the progressive, low-amplitude shortwave trough.
Moreover warmer air aloft accompanying a northeastward-expanding
elevated mixed layer will slowly overspread the region from the
southwest. These processes might contribute to limiting factors for
a more robust severe threat. Nevertheless, storms along the southern
end of the MCS may redevelop/intensify along the residual outflow
boundary as the downstream atmosphere destabilizes, supporting a
risk for a few instances of damaging wind and hail into the
afternoon. Have therefore introduced a marginal risk category for
this region, and trends will continue to be monitored for a possible
slight risk in upcoming day 1 updates.
Farther west the warm sector will destabilize from across eastern
TX, but warm advection aloft accompanying the
northeastward-expanding elevated mixed layer and weak forcing should
inhibit additional thunderstorm development. However, storms may
develop Monday evening or overnight north of the warm front across a
portion of AR. These storms will be elevated, but the stronger
storms may pose some risk for small to marginally severe hail.