ACUS01 KWNS 190041
SPC AC 190040
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0640 PM CST Sat Nov 18 2017
Valid 190100Z - 191200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THROUGH MID TO
LATE EVENING ACROSS PARTS OF THE UPPER TENNESSEE VALLEY INTO THE
CENTRAL AND SOUTHERN APPALACHIANS...
A remnant band of thunderstorms approaching the central and southern
Appalachians region may continue to be accompanied by locally
damaging wind gusts through about 8-9 PM EST.
...01Z Outlook Update...
Strong mid/upper forcing for ascent, associated with a vigorous
short wave trough progressing east of the Mississippi Valley, is
maintaining convective development across eastern Kentucky and
Tennessee into portions of northern Alabama. As activity advances
into a progressively cooler and drier low-level environment near the
central and southern Appalachians, thermodynamic profiles are
becoming less conducive for the development of charge separation and
lightning. However, remnant convection may continue to aid the
downward transfer of high momentum air to the surface, resulting in
a continuing risk for localized damaging surface gusts.
As the cold front reaches the crest of the southern Appalachians
toward 03-04Z, the risk for deeper convection enhanced wind gusts
seems likely to diminish.
The risk for pre-frontal thunderstorm activity east of the
Appalachians later tonight is more unclear. However, latest
forecast soundings from the Rapid Refresh continue to suggest this
potential is generally low, but perhaps maximized on the
southeastern fringe of the mid-level trough as it pivots toward the
Atlantic Coast. This is where a modest influx of moisture could
contribute to weak CAPE through the favorable mixed phase layer for
charge separation. Any such activity is expected to be elevated
above a neutral to stable near-surface layer, which may tend to
limit potential for convectively enhanced gusts to reach the
surface. Given the apparent low probabilities for thunderstorms,
severe wind probabilities still seem less than 5 percent.