SPC AC 140728
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Tue Aug 14 2018
Valid 161200Z - 171200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE CENTRAL PLAINS AS WELL AS THE LOWER MISSISSIPPI...TENNESSEE
AND OHIO VALLEYS...
A few strong to severe storms will be possible Thursday over a part
of the central Plains, as well as from the lower Mississippi Valley
into the Tennessee and Ohio Valleys.
Deamplifying shortwave trough will move northeast through the Ohio
Valley, while an upstream impulse embedded within northwest flow
advances southeast through the Central Plains and middle MS Valley.
A convectively reinforced front will advance slowly south through
the central Plains, while a weaker front/trough accompanies the
shortwave trough into the OH Valley, with trailing portion extending
southwest into OK.
...Central Plains into the middle Mississippi Valley...
A moist warm sector with dewpoints in the mid to upper 60s should
reside in vicinity of front beneath modest (7 C/km) mid-level lapse
rates, and the atmosphere will likely become moderately unstable as
the surface layer warms during the day. Storms may be ongoing within
zone of ascent along/north of the front across a part of NE, but
with new development likely during the afternoon along the front and
residual outflow boundaries as the surface layer destabilizes. A
belt of modest northwesterly winds aloft accompanying the shortwave
trough will support 35-45 kt effective bulk shear. A few organized
storms including embedded supercell structures capable of isolated
large hail and damaging wind are possible with some potential for
upscale growth into a small MCS during the evening. Have introduced
a marginal risk for this outlook, but a slight risk may be needed in
...Ohio, Tennessee and lower Mississippi Valley regions...
A belt of stronger winds in the 850-700 mb layer is forecast to
accompany the shortwave trough the OH Valley region during the day.
Areas of showers and storms with widespread clouds will likely be in
progress early Thursday within plume of subtropical moisture and
weak cap. However, partial clearing and pockets of heating may
occur, especially south of the warm conveyor belt, and additional
storms may develop during the afternoon. While vertical shear will
remain weak, the stronger flow in the 850-500 mb layer may increase
the threat for locally strong to damaging wind gusts with
redevelopment of multicells and line segments during the afternoon.
Other storms may develop along trailing part of the boundary as far
back as AR and OK. Uncertainty regarding evolution of the
thermodynamic environment precludes more than a marginal risk this
update, but area will continue to be monitored for a possible slight
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