- Day Three
acus02 kwns 231723
Storm Prediction Center ac 231723
Day 2 convective outlook corr 1
National Weather Service Storm Prediction Center Norman OK
1223 PM CDT sun Sep 23 2018
Valid 241200z - 251200z
..there is a marginal risk of severe thunderstorms over a portion
of the Tennessee and Ohio valleys...
Corrected for categorical graphic
A strong thunderstorm or two may impact portions of the Tennessee
and lower Ohio Valley Monday afternoon and evening, accompanied by a
marginal risk for severe weather.
A positive-tilt upper trough currently over the northern rockies
will advance east through the northern plains and upper MS valley
region Monday. A weaker southern-stream shortwave trough now over
the lower MS valley will move northeast through the Tennessee and Ohio
valleys. The northern-stream trough will be accompanied by a cold
front through the upper MS valley. Farther south, the western
portion of a quasi-stationary front now from the Carolinas westward
into the Tennessee Valley will lift north as a warm front into the Ohio
..Tennessee into the Ohio Valley...
A modest southerly low-level jet is forecast to develop in response
to forcing associated with the southern-stream trough, and this
feature will migrate northward through the Tennessee and Ohio valleys. A
moist warm sector with low 70s f dewpoints will reside in warm
sector south of the warm front, but weak lapse rates with areas of
clouds and ongoing rain within plume of deep subtropical moisture
will limit destabilization potential. Nevertheless, at least weak
instability with 500 j/kg MLCAPE will exist, and low-level
hodographs will increase in size along the low-level jet axis,
though flow through a deeper layer will remain weak. This
environment may support at least a marginal risk for a couple of
transient rotating updrafts and northeast-moving bowing segments
with primary threats being locally strong wind gusts and a brief
..upper Mississippi Valley region...
Overall severe potential in this region appears very limited.
Widespread clouds, weak lapse rates and limited low-level moisture
with dewpoints in the 50s f will result in very weak instability
with MLCAPE near or below 300 j/kg. Showers and possibly isolated
thunderstorms should develop within the zone of deeper ascent along
the cold front from Minnesota into eastern SD, and this activity will be
embedded within a kinematic environment favorable for severe storms
with sfc-6 km shear around 40-45 kt. However, the very marginal
thermodynamic environment is expected to limit the severe threat in
..maximum risk by hazard...
Tornado: 2% - marginal
wind: 5% - marginal
hail: <5% - none