Valid 312000Z – 011200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN
KENTUCKY INTO FAR WEST-CENTRAL VIRGINIA…
A few strong storms are possible across parts of the Ohio Valley to
central Appalachians this afternoon.
No significant changes were made to the previous outlook. Only
isolated storms are expected along the east-west instability axis
from northern KY into far western VA, aided by strong heating. 18Z
soundings indicate a subsidence inversion aloft, and weak shear,
with only short lived, marginal wind or hail expected.
.PREV DISCUSSION… /ISSUED 1130 AM CDT Sat Aug 31 2019/
…Ohio Valley to central Appalachians…
Robust boundary-layer heating near a weakly convergent
quasi-stationary front, ahead of a decaying mid-level impulse,
should aid in isolated thunderstorms forming by mid afternoon. A
confined corridor of modest buoyancy should develop, characterized
by MLCAPE of 1000-1500 J/kg. While low-level winds will be weak, a
belt of 25-30 kt 500-mb southwesterlies should support transient
updraft rotation in a few cells. This may yield locally strong wind
gusts along with marginally severe hail.
…Northern Nebraska to southern/eastern South Dakota…
While overall forcing for ascent will be limited, sufficient
moist/convergence could influence isolated thunderstorm development
near a weak surface/boundary across northern Nebraska/southern South
Dakota. If storms develop, a severe storm or two cannot be entirely
ruled out given adequate buoyancy and moderately strong
northwesterly flow aloft. Storms are a bit more likely to develop
later tonight across eastern South Dakota with increasing warm
advection, although hail potential will tend to be limited by modest
mid-level lapse rates. Overall scenario across the region currently
appears too marginal/uncertain to warrant severe probabilities.
An isolated storm or two could develop over/near the mountains of
southeast Arizona this afternoon and drift generally westward.
However, storm organization should be limited by weaker mid-level
winds, while the strongest updrafts should be relegated to south of
the international border. As such, severe wind probabilities do not