Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS01 KWNS 250043
SPC AC 250041
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0641 PM CST Fri Feb 24 2017
Valid 250100Z - 251200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTH
CENTRAL OHIO SOUTH-SOUTHWEST INTO CENTRAL KENTUCKY...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EXTENDING FROM
SOUTHEAST LOWER MICHIGAN AND LAKE ERIE SOUTH-SOUTHWEST INTO
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
SLIGHT AND ENHANCED RISK AREAS...
Strong to severe thunderstorms are forecast to continue affecting
areas from southeast Lower Michigan southward to Tennessee this
evening and tonight. The primary threat appears to be damaging wind,
but some hail and a tornado or two will be possible.
Two main bands of thunderstorms are ongoing at this time per latest
radar imagery -- one extending from southeast Lower Michigan
south-southwest to western Kentucky along an advancing cold front,
and a second from western Lake Erie south-southwest to northern
Middle Tennessee along a pre-frontal confluence axis. The strongest
of the bands remains the more eastern one, where a few recent
reports of marginal hail and local wind damage have been reported
with stronger/rotating updrafts within the band. Meanwhile farther
west, storms have remained sub-severe, though some local
intensification has been noted recently.
Overall, it appears that this two-banded convective structure will
continue over the next few hours, possibly merging into one larger
zone of convection with time as the cold front accelerates eastward.
The leading band is moving through an axis of around 500 J/kg
mixed-layer CAPE (per objective analysis and evening RAOBs), and
with roughly 50 kt 0-6 km shear present across the area, severe risk
will likely persist until storms encounter a less unstable
environment over eastern Ohio and far eastern Kentucky. Farther
south, storms may expand across Tennessee and into northern Alabama,
along with isolated risk for damaging winds and/or hail.
Meanwhile, as the approaching upper trough takes on neutral to
slightly negative tilt into the overnight hours, the more western
band of convection may grow upscale into a low-topped,
semi-continuous line of frontal storms. Despite weaker instability
-- particularly given the pre-frontal band of storms farther east
which continues to process existing CAPE, potential nonetheless
remains for a few locally damaging wind gusts to emanate from
stronger line segments.