Columbus, OH...Memphis, TN...Charlotte, NC...Oklahoma City, OK...Nashville, TN...
SPC AC 211731
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1231 PM CDT Thu Jun 21 2018
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL/SOUTHERN PLAINS AND SOUTHEAST...
Scattered severe storms will be possible across parts of the
central/southern Plains and southeast US on Friday.
Initial mid-level ridging over the High Plains will yield to an
upstream trough, characterized by several embedded impulses, which
will overspread the region during peak heating. Broad forcing for
ascent will support a deepening surface low over the southern High
Plains, with increasing upslope flow over Colorado and surface
convergence southward into the Texas/Oklahoma Panhandles. Surface
dew points rising into the 50s/lower 60s and strong heating (once
low-level cloud cover dissipates) should support at least 1000-1500
J/kg of MLCAPE, with much of this buoyancy residing in the favored
-10 to -30 C zone for hail growth. Combined with ample veering of
flow with height, this thermodynamic environment will be supportive
of initial supercells capable of very large hail, damaging winds,
and perhaps a tornado or two.
Through the evening hours, an amplifying low-level jet will likely
foster upscale growth into one or more east/southeastward-moving
convective systems, with damaging winds becoming the primary threat.
Although surface-based inhibition will rise given nocturnal cooling,
residual steep mid-level lapse rates and dry air aloft may allow a
mature convective system (characterized by a well-established cold
pool) to make farther eastward progress than would be expected of
individual cells alone. As such, continued adjustments to the
outlook will likely be needed.
...Southeast US to the Ohio Valley...
500mb flow will be anomalously strong over much of the Southeast
Friday (based on sounding climo for various sites), such that
pockets of storms will exhibit more organization than what would be
otherwise expected for mid/late June here. Still, the potential for
early-day convection and related cloud cover/overturning/outflow
lends considerable spatial uncertainty with regards to
destabilization and convective initiation during peak heating.
Across the lower Mississippi Valley, strong storms may be ongoing
Friday morning, given a lobe of ascent dropping southeast along the
periphery of a closed low centered over the Midwest. To the
west/southwest of these storms, heating through the day should yield
at least moderate instability. However, increasing subsidence aloft
and southward-advancing outflow may: (a) Decouple new development
from stronger flow aloft and (b) Cause cells to become elevated atop
outflow relatively quickly. Still, a conditional threat will exist
for large hail, damaging winds, and perhaps a tornado or two, and no
change is made to the ongoing slight risk here.
Farther east, downstream cloud cover from the aforementioned
convection may slow destabilization over parts of Mississippi and
Alabama, and a relative minimum in storm coverage may be realized in
some areas. Nonetheless, where heating does occur, enhanced
unidirectional flow will likely encourage small linear segments with
an attendant damaging wind threat, as they move east during the
afternoon and evening. An embedded tornado or two may be possible as
well. This risk should extend farther northeast towards Kentucky and
Virginia, and the marginal risk has been expanded accordingly. Some
of these areas may require an upgrade to slight risk, pending
greater confidence in the focus of destabilization and convective
...MAXIMUM RISK BY HAZARD...
Tornado: 5% - Slight
Wind: 15% - Slight
Hail: 15% SIG - Slight
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z