Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
SPC AC 201628
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Fri Jul 20 2018
Valid 201630Z - 211200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
KENTUCKY...SOUTHERN/EASTERN INDIANA...AND SOUTHWESTERN OHIO...
The greatest threat for severe thunderstorms will develop across the
Ohio and Tennessee Valley regions into the Mid-South today into
early tonight, with damaging gusts, large hail and tornadoes
...Mid MS/OH/TN Valleys...
Morning water vapor loop shows a significant upper low tracking
southeastward across southern WI. A strong mid level jet lies to
the south of the low, extending from the northern Plains into MO.
As this upper wind max overspreads the warm sector over parts of the
Mid MS, OH, and TN Valleys, the risk of rather widespread severe
thunderstorms will develop this afternoon into tonight. A very
moist and unstable air mass has developed across this region with
pockets of MUCAPE in the 5000-6000 J/kg range. Steep low and mid
level lapse rates combined with strong effective shear values will
result in a conditional risk of severe storms throughout the region.
The primary forecast uncertainty is the timing and location of
12z model guidance shows wide diversity in where/when the most
intense convective clusters will occur later today. Due to this
uncertainty, few changes have been made to the ongoing outlook.
Discrete supercell development is possible along/ahead of the
approaching cold front due to shear vectors orthogonal to the front
and favorable shear magnitudes. Any storms that remain discrete
will pose a risk of very large hail and a tornado or two. It
appears likely that multiple clusters of storms will congeal into
fast-moving bowing structures posing a risk of rather widespread
damaging winds. This threat will likely spread as far east as
eastern KY/TN overnight.
...KS/MO/OK/AR this evening...
A surface boundary will extend from western KS into southwest MO and
northwest AR later today. Given the intense heat to the south of
boundary, and a corridor of high dewpoints immediately north of the
boundary, a zone of high CAPE values will result. There is
relatively good consensus of 12z models that show clusters of storms
forming over KS late this afternoon and tracking along this corridor
though the evening. Damaging winds and large hail will be possible
if this scenario unfolds.
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z